Soils in the Humid Tropics and Monsoon Region of Indonesia 9781420069075, 1420069071

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Soils in the Humid Tropics and Monsoon Region of Indonesia

BOOKS IN SOILS, PLANTS, AND THE ENVIRONMENT

Editorial Board Agricultural Engineering

Robert M. Peart, University of Florida, Gainesville

Crops

Mohammad Pessarakli, University of Arizona, Tucson

Environment

Kenneth G. Cassman, University of Nebraska, Lincoln

Irrigation and Hydrology

Donald R. Nielsen, University of California, Davis

Microbiology

Jan Dirk van Elsas, Research Institute for Plant Protection, Wageningen, The Netherlands

Plants

L. David Kuykendall, U.S. Department of Agriculture, Beltsville, Maryland Kenneth B. Marcum, Arizona State University, Tempe

Soils

Jean-Marc Bollag, Pennsylvania State University, University Park Tsuyoshi Miyazaki, University of Tokyo, Japan

Soil Biochemistry, edited by A. D. McLaren and G. H. Peterson Soil Biochemistry, edited by A. D. McLaren and J. Skujins Soil Biochemistry, edited by E. A. Paul and A. D. McLaren Soil Biochemistry, edited by E. A. Paul and A. D. McLaren Soil Biochemistry, edited by E. A. Paul and J. N. Ladd Soil Biochemistry, edited by Jean-Marc Bollag and G. Stotzky Soil Biochemistry, edited by G. Stotzky and Jean-Marc Bollag Soil Biochemistry, edited by Jean-Marc Bollag and G. Stotzky Soil Biochemistry, edited by G. Stotzky and Jean-Marc Bollag Organic Chemicals in the Soil Environment, edited by C. A. I. Goring and J. W. Hamaker Humic Substances in the Environment, M. Schnitzer and S. U. Khan Microbial Life in the Soil: An Introduction, T. Hattori Principles of Soil Chemistry, Kim H. Tan Soil Analysis: Instrumental Techniques and Related Procedures, edited by Keith A. Smith

Soil Reclamation Processes: Microbiological Analyses and Applications, edited by Robert L. Tate III and Donald A. Klein Symbiotic Nitrogen Fixation Technology, edited by Gerald H. Elkan Soil–Water Interactions: Mechanisms and Applications, Shingo Iwata and Toshio Tabuchi with Benno P. Warkentin Soil Analysis: Modern Instrumental Techniques, Second Edition, edited by Keith A. Smith Soil Analysis: Physical Methods, edited by Keith A. Smith and Chris E. Mullins Growth and Mineral Nutrition of Field Crops, N. K. Fageria, V. C. Baligar, and Charles Allan Jones Semiarid Lands and Deserts: Soil Resource and Reclamation, edited by J. Skujins Plant Roots: The Hidden Half, edited by Yoav Waisel, Amram Eshel, and Uzi Kafkafi Plant Biochemical Regulators, edited by Harold W. Gausman Maximizing Crop Yields, N. K. Fageria Transgenic Plants: Fundamentals and Applications, edited by Andrew Hiatt Soil Microbial Ecology: Applications in Agricultural and Environmental Management, edited by F. Blaine Metting, Jr. Principles of Soil Chemistry: Second Edition, Kim H. Tan Water Flow in Soils, edited by Tsuyoshi Miyazaki Handbook of Plant and Crop Stress, edited by Mohammad Pessarakli Genetic Improvement of Field Crops, edited by Gustavo A. Slafer Agricultural Field Experiments: Design and Analysis, Roger G. Petersen Environmental Soil Science, Kim H. Tan Mechanisms of Plant Growth and Improved Productivity: Modern Approaches, edited by Amarjit S. Basra Selenium in the Environment, edited by W. T. Frankenberger, Jr. and Sally Benson Plant–Environment Interactions, edited by Robert E. Wilkinson Handbook of Plant and Crop Physiology, edited by Mohammad Pessarakli Handbook of Phytoalexin Metabolism and Action, edited by M. Daniel and R. P. Purkayastha Soil–Water Interactions: Mechanisms and Applications, Second Edition, Revised and Expanded, Shingo Iwata, Toshio Tabuchi, and Benno P. Warkentin Stored-Grain Ecosystems, edited by Digvir S. Jayas, Noel D. G. White, and William E. Muir Agrochemicals from Natural Products, edited by C. R. A. Godfrey Seed Development and Germination, edited by Jaime Kigel and Gad Galili

Nitrogen Fertilization in the Environment, edited by Peter Edward Bacon Phytohormones in Soils: Microbial Production and Function, William T. Frankenberger, Jr., and Muhammad Arshad Handbook of Weed Management Systems, edited by Albert E. Smith Soil Sampling, Preparation, and Analysis, Kim H. Tan Soil Erosion, Conservation, and Rehabilitation, edited by Menachem Agassi Plant Roots: The Hidden Half, Second Edition, Revised and Expanded, edited by Yoav Waisel, Amram Eshel, and Uzi Kafkafi Photoassimilate Distribution in Plants and Crops: Source–Sink Relationships, edited by Eli Zamski and Arthur A. Schaffer Mass Spectrometry of Soils, edited by Thomas W. Boutton and Shinichi Yamasaki Handbook of Photosynthesis, edited by Mohammad Pessarakli Chemical and Isotopic Groundwater Hydrology: The Applied Approach, Second Edition, Revised and Expanded, Emanuel Mazor Fauna in Soil Ecosystems: Recycling Processes, Nutrient Fluxes, and Agricultural Production, edited by Gero Benckiser Soil and Plant Analysis in Sustainable Agriculture and Environment, edited by Teresa Hood and J. Benton Jones, Jr. Seeds Handbook: Biology, Production, Processing, and Storage, B. B. Desai, P. M. Kotecha, and D. K. Salunkhe Modern Soil Microbiology, edited by J. D. van Elsas, J. T. Trevors, and E. M. H. Wellington Growth and Mineral Nutrition of Field Crops: Second Edition, N. K. Fageria, V. C. Baligar, and Charles Allan Jones Fungal Pathogenesis in Plants and Crops: Molecular Biology and Host Defense Mechanisms, P. Vidhyasekaran Plant Pathogen Detection and Disease Diagnosis, P. Narayanasamy Agricultural Systems Modeling and Simulation, edited by Robert M. Peart and R. Bruce Curry Agricultural Biotechnology, edited by Arie Altman Plant–Microbe Interactions and Biological Control, edited by Greg J. Boland and L. David Kuykendall Handbook of Soil Conditioners: Substances That Enhance the Physical Properties of Soil, edited by Arthur Wallace and Richard E. Terry Environmental Chemistry of Selenium, edited by William T. Frankenberger, Jr., and Richard A. Engberg Principles of Soil Chemistry: Third Edition, Revised and Expanded, Kim H. Tan Sulfur in the Environment, edited by Douglas G. Maynard Soil–Machine Interactions: A Finite Element Perspective, edited by Jie Shen and Radhey Lal Kushwaha

Mycotoxins in Agriculture and Food Safety, edited by Kaushal K. Sinha and Deepak Bhatnagar Plant Amino Acids: Biochemistry and Biotechnology, edited by Bijay K. Singh Handbook of Functional Plant Ecology, edited by Francisco I. Pugnaire and Fernando Valladares Handbook of Plant and Crop Stress: Second Edition, Revised and Expanded, edited by Mohammad Pessarakli Plant Responses to Environmental Stresses: From Phytohormones to Genome Reorganization, edited by H. R. Lerner Handbook of Pest Management, edited by John R. Ruberson Environmental Soil Science: Second Edition, Revised and Expanded, Kim H. Tan Microbial Endophytes, edited by Charles W. Bacon and James F. White, Jr. Plant–Environment Interactions: Second Edition, edited by Robert E. Wilkinson Microbial Pest Control, Sushil K. Khetan Soil and Environmental Analysis: Physical Methods, Second Edition, Revised and Expanded, edited by Keith A. Smith and Chris E. Mullins The Rhizosphere: Biochemistry and Organic Substances at the Soil–Plant Interface, Roberto Pinton, Zeno Varanini, and Paolo Nannipieri Woody Plants and Woody Plant Management: Ecology, Safety, and Environmental Impact, Rodney W. Bovey Metals in the Environment, M. N. V. Prasad Plant Pathogen Detection and Disease Diagnosis: Second Edition, Revised and Expanded, P. Narayanasamy Handbook of Plant and Crop Physiology: Second Edition, Revised and Expanded, edited by Mohammad Pessarakli Environmental Chemistry of Arsenic, edited by William T. Frankenberger, Jr. Enzymes in the Environment: Activity, Ecology, and Applications, edited by Richard G. Burns and Richard P. Dick Plant Roots: The Hidden Half,Third Edition, Revised and Expanded, edited by Yoav Waisel, Amram Eshel, and Uzi Kafkafi Handbook of Plant Growth: pH as the Master Variable, edited by Zdenko Rengel Biological Control of Major Crop Plant Diseases edited by Samuel S. Gnanamanickam Pesticides in Agriculture and the Environment, edited by Willis B. Wheeler Mathematical Models of Crop Growth and Yield, , Allen R. Overman and Richard Scholtz

Plant Biotechnology and Transgenic Plants, edited by Kirsi-Marja Oksman Caldentey and Wolfgang Barz Handbook of Postharvest Technology: Cereals, Fruits, Vegetables,Tea, and Spices, edited by Amalendu Chakraverty, Arun S. Mujumdar, G. S. Vijaya Raghavan, and Hosahalli S. Ramaswamy Handbook of Soil Acidity, edited by Zdenko Rengel Humic Matter in Soil and the Environment: Principles and Controversies, edited by Kim H. Tan Molecular Host Plant Resistance to Pests, edited by S. Sadasivam and B. Thayumanayan Soil and Environmental Analysis: Modern Instrumental Techniques, Third Edition, edited by Keith A. Smith and Malcolm S. Cresser Chemical and Isotopic Groundwater Hydrology,Third Edition, edited by Emanuel Mazor Agricultural Systems Management: Optimizing Efficiency and Performance, edited by Robert M. Peart and W. David Shoup Physiology and Biotechnology Integration for Plant Breeding, edited by Henry T. Nguyen and Abraham Blum Global Water Dynamics: Shallow and Deep Groundwater: Petroleum Hydrology: Hydrothermal Fluids, and Landscaping, , edited by Emanuel Mazor Principles of Soil Physics, edited by Rattan Lal Seeds Handbook: Biology, Production, Processing, and Storage, Second Edition, Babasaheb B. Desai Field Sampling: Principles and Practices in Environmental Analysis, edited by Alfred R. Conklin Sustainable Agriculture and the International Rice-Wheat System, edited by Rattan Lal, Peter R. Hobbs, Norman Uphoff, and David O. Hansen Plant Toxicology, Fourth Edition, edited by Bertold Hock and Erich F. Elstner Drought and Water Crises: Science,Technology, and Management Issues, edited by Donald A. Wilhite Soil Sampling, Preparation, and Analysis, Second Edition, Kim H. Tan Climate Change and Global Food Security, edited by Rattan Lal, Norman Uphoff, B. A. Stewart, and David O. Hansen Handbook of Photosynthesis, Second Edition, edited by Mohammad Pessarakli Environmental Soil-Landscape Modeling: Geographic Information Technologies and Pedometrics, edited by Sabine Grunwald Water Flow In Soils, Second Edition, Tsuyoshi Miyazaki Biological Approaches to Sustainable Soil Systems, edited by Norman Uphoff, Andrew S. Ball, Erick Fernandes, Hans Herren, Olivier Husson, Mark Laing, Cheryl Palm, Jules Pretty, Pedro Sanchez, Nteranya Sanginga, and Janice Thies

Plant–Environment Interactions,Third Edition, edited by Bingru Huang Biodiversity In Agricultural Production Systems, edited by Gero Benckiser and Sylvia Schnell Organic Production and Use of Alternative Crops, Franc Bavec and Martina Bavec Handbook of Plant Nutrition, edited by Allen V. Barker and David J. Pilbeam Modern Soil Microbiology, Second Edition, edited by Jan Dirk van Elsas, Janet K. Jansson, and Jack T. Trevors Functional Plant Ecology, Second Edition, edited by Francisco I. Pugnaire and Fernando Valladares Fungal Pathogenesis in Plants and Crops: Molecular Biology and Host Defense Mechanisms Second Edition, P. Vidhyasekaran Handbook of Turfgrass Management and Physiology, edited by Mohammad Pessarakli Soils in the Humid Tropics and Monsoon Region of Indonesia, Kim H. Tan

Soils in the Humid Tropics and Monsoon Region of Indonesia Kim H. Tan University of Georgia Athens, Georgia

Boca Raton London New York

CRC Press is an imprint of the Taylor & Francis Group, an informa business

CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2008 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number-13: 978-1-4200-6907-5 (Hardcover) This book contains information obtained from authentic and highly regarded sources Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The Authors and Publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www. copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Tan, Kim H. (Kim Howard), 1926Soils in the humid tropics and monsoon region of Indonesia / Kim H. Tan. p. cm. -- (Books in soils, plants, and the environment ; 123) Includes bibliographical references and index. ISBN 978-1-4200-6907-5 (alk. paper) 1. Soils--Indonesia. 2. Soils--Tropics. I. Title. II. Series. S599.6.I5T36 2008 631.4’9598--dc22 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com

2007050715

Contents Preface ............................................................................. xv Acknowledgments ...................................................... xxv Chapter 1 1.1 1.2

The development of soil science in Indonesia....................................................1 The pre-World War II period .............................2 The post-World War II period ............................6 1.2.1 The establishment of higher education .................................................8 1.2.2 The Kentucky Contract Team (KCT) and Midwestern Universities Consortium for International Activities (MUCIA) projects ................11 1.2.3 Pedology ................................................13 1.2.4 Soil survey .............................................14 1.2.5 Soil fertility and plant nutrition .........15 1.2.6 The dawn of new experiment stations ...................................................17 1.2.7 National conferences and scientiic societies..................................................19 1.2.8 Land use and soil conservation ..........20

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Contents

Chapter 2 Geomorphology of Indonesia.................27 2.1 Geographical setting of Indonesia ..................27 2.2 Geomorphology of major islands ....................30 2.2.1 Geomorphological features of Java ....31 2.2.2 Geomorphological features of Sumatra..................................................35 2.2.3 Geomorphological features of Kalimantan............................................38 2.2.4 Geomorphological features of Sulawesi .................................................41 2.2.5 Geomorphological features of Maluku ..................................................44 2.2.5.1 Ambon ...................................45 2.2.5.2 Ceram .....................................46 2.2.6 Geomorphological features of Nusa Tenggara ......................................46 2.2.7 Geomorphological features of Papua (West Irian) ................................47 Chapter 3 Climate of Indonesia ................................51 3.1 Climate ...............................................................51 3.1.1 The concepts of equatorial and tropical climates....................................52 3.1.1.1 Equatorial climate .................52 3.1.1.2 Tropical climate .....................54 3.1.2 The concept of monsoon climates ......55 3.1.2.1 Concept of monsoons ...........55 3.1.2.2 West and east monsoons in Indonesia ...........................59 3.2 Climatic divisions based on length of dry and wet seasons.................................................61

Contents

xiii 3.2.1 3.2.2

3.3

3.4

The climatic system of Mohr ..............62 Climatic system of Schmidt and Ferguson ................................................65 Altitudinal variations in climate .....................67 3.3.1 Variations in rainfall patterns with altitude ...................................................68 3.3.2 Variations in temperatures with altitude ...................................................68 3.3.3 Zonal divisions into lowland, upland, mountain, and highmountain lands.....................................67 Signiicance of tropical and monsoon climates in pedogenesis....................................72 3.4.1 Balance effects between precipitation and evaporation in different climatic types ........................73 3.4.2 Altitudinal variations in soil genesis and soil fertility ......................74

Chapter 4 Vegetation of Indonesia.......................... 77 4.1 Climax vegetation .............................................77 4.1.1 The tropical rain forest ........................77 4.1.2 The tropical monsoon forest ...............78 4.1.3 The tropical Savannah forest ..............79 4.2 Vegetation provinces.........................................79 4.2.1 West Indonesian vegetation province .................................................80 4.2.2 East Indonesian vegetation province .................................................80 4.2.3 South Indonesian vegetation province .................................................81 4.3 Altitudinal vegetation zones............................84

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Contents 4.3.1 4.3.2 4.3.3 4.3.4

Chapter 5 5.1 5.2

5.3 5.4

The coastal lora ....................................84 The rain forest and the mountain rain forest ..............................................88 The cloud-belt forest.............................89 The subalpine vegetation.....................90

Soil formation, classiication, and land use ...................................................93 Soil-formation factors........................................93 Soil-forming processes .....................................94 5.2.1 Previous concept of soil-forming processes ................................................96 5.2.2 Today’s versions of soil-forming processes ..............................................102 5.2.2.1 Desiliciication .....................102 5.2.2.2 Siliciication .........................103 5.2.2.3 Translocation of clays .........104 5.2.2.4 Translocation of aluminum and iron ............106 5.2.2.5 Redox reactions ...................108 5.2.3 Inluence of climatic variations on soil-forming processes ....................... 110 5.2.3.1 Mineralization versus humiication ........................ 110 5.2.4 Inluence of parent materials on soil formation ...................................... 115 5.2.5 Precipitation/evaporation ratio and weathering intensity .......................... 117 The system of soil classiication in Indonesia ..........................................................121 Land use in Indonesia ....................................125

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Chapter 6 Soils in the lowlands of Indonesia ..... 129 6.1 Introduction .....................................................129 6.2 Oxisols ..............................................................130 6.2.1 Parent materials ..................................132 6.2.2 Climate.................................................138 6.2.3 Soil morphology .................................142 6.2.4 Soil classiication ................................148 6.2.5 Physicochemical characteristics........153 6.2.5.1 Particle size distribution ....153 6.2.5.2 Chemical characteristics ....154 6.2.5.3 Charge characteristics ........157 6.2.5.4 Clay mineralogy .................159 6.2.6 Land use and evaluation ................... 161 6.2.6.1 Evaluation of analytical properties ............................. 161 6.2.6.2 Signiicance of basic soil properties .............................164 6.2.6.3 Agricultural operations .....165 6.3 Ultisols ..............................................................177 6.3.1 Parent materials ..................................179 6.3.2 Climate................................................. 181 6.3.3 Soil morphology .................................182 6.3.4 Soil classiication ................................186 6.3.5 Physicochemical characteristics........190 6.3.5.1 Particle size distribution ....190 6.3.5.2 Chemical characteristics ....192 6.3.5.3 Charge characteristics ........193 6.3.5.4 Clay mineralogy .................194 6.3.6 Land use and evaluation ...................197 6.3.6.1 Evaluation of analytical properties .............................197

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Contents 6.3.6.2

6.4

6.5

Signiicance of basic soil properties .............................199 6.3.6.3 Agricultural operations .....200 Lowland alisols ..............................................209 6.4.1 Parent materials .................................. 210 6.4.2 Climate.................................................212 6.4.3 Soil morphology .................................213 6.4.4 Soil classiication ................................215 6.4.5 Physicochemical characteristics........ 218 6.4.5.1 Particle size distribution ....218 6.4.5.2 Chemical characteristics .... 218 6.4.5.3 Clay mineralogy .................220 6.4.6 Land use and evaluation ...................221 6.4.6.1 Evaluation of analytical properties .............................221 6.4.6.2 Signiicance of basic soil properties .............................221 6.4.6.3 Agricultural operations .....222 Vertisols ............................................................227 6.5.1 Parent materials ..................................228 6.5.2 Climate.................................................230 6.5.3 Soil morphology .................................232 6.5.4 Soil classiication ................................235 6.5.5 Physicochemical characteristics........237 6.5.5.1 Particle size distribution ....237 6.5.5.2 Chemical characteristics ....238 6.5.5.3 Clay mineralogy .................239 6.5.6 Land use and evaluation ...................242 6.5.6.1 Evaluation of analytical properties .............................242 6.5.6.2 Signiicance of basic soil properties .............................242

Contents 6.6

xvii

6.5.6.3 Agricultural operations .....244 Histosols ...........................................................253 6.6.1 Parent materials ..................................258 6.6.1.1 Decomposition of litter and genesis of peat .............261 6.6.2 Climate.................................................262 6.6.3 Soil morphology .................................264 6.6.4 Soil classiication ................................267 6.6.5 Physicochemical characteristics........270 6.6.5.1 Acidity of peat .....................270 6.6.5.2 Nutrient status of peat .......273 6.6.5.3 Aluminum contents in peat .......................................275 6.6.5.4 Carbon contents and Corg sequestration by peat..........275 6.6.5.5 Physical properties .............277 6.6.6 Land use and evaluation ...................282 6.6.6.1 Evaluation of analytical properties .............................282 6.6.6.2 Signiicance of basic properties .............................283 6.6.6.3 Agricultural operations .....286

Chapter 7 Soils in the uplands of Indonesia ........293 7.1 Introduction .....................................................293 7.2 Podzolic latosols ..............................................294 7.3 Inceptisols ........................................................296 7.3.1 Parent materials ..................................299 7.3.2 Climate.................................................302 7.3.3 Soil morphology .................................304 7.3.4 Soil classiication ................................306 7.3.5 Physicochemical characteristics........309

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Contents

7.3.6

7.3.5.1 Particle size distribution ....309 7.3.5.2 Chemical characteristics .... 311 7.3.5.3 Clay mineralogy .................312 Land use and evaluation ...................313 7.3.6.1 Evaluation of analytical properties .............................313 7.3.6.2 Signiicance of basic soil properties .............................315 7.3.6.3 Agricultural operations ..... 316

Chapter 8 Soils in the mountains of Indonesia .. 333 8.1 Introduction .....................................................333 8.2 Highland alisols .............................................337 8.2.1 Parent materials ..................................338 8.2.2 Climate.................................................340 8.2.3 Soil morphology .................................341 8.2.4 Soil classiication ............................... 344 8.2.5 Physicochemical characteristics........347 8.2.5.1 Particle size distribution ....347 8.2.5.2 Chemical characteristics ....347 8.2.5.3 Clay mineralogy .................349 8.2.6 Land use and evaluation ...................352 8.2.6.1 Evaluation of analytical properties .............................352 8.2.6.2 Signiicance of basic soil properties .............................352 8.2.6.3 Agricultural operations .....353 8.3 Brown podzolic soils ......................................367 8.3.1 Parent materials ..................................369 8.3.2 Climate.................................................370 8.3.3 Soil morphology .................................372 8.3.4 Soil classiication ................................ 374

Contents

xix 8.3.5

8.4

Physicochemical characteristics........375 8.3.5.1 Particle size distribution ....375 8.3.5.2 Chemical characteristics .... 376 8.3.5.3 Clay mineralogy .................377 8.3.6 Land use and evaluation ...................379 Spodosols .........................................................380 8.4.1 Parent materials ..................................383 8.4.2 Climate.................................................385 8.4.3 Soil morphology .................................387 8.4.4 Soil classiication ................................390 8.4.5 Physicochemical characteristics........392 8.4.5.1 Particle size distribution ....392 8.4.5.2 Chemical characteristics ....392 8.4.5.3 Clay mineralogy .................394 8.4.6 Land use and evaluation ...................396 8.4.6.1 Soil properties and agricultural operations.......396 8.4.6.2 Tree farming ........................397

Chapter 9 9.1 9.2 9.3 9.4 9.5 9.6

Andosols of Indonesia ...........................399

Introduction .....................................................399 Parent materials ...............................................402 Climate .............................................................405 Soil morphology ..............................................407 Soil classiication ............................................. 411 Physicochemical characteristics ....................417 9.6.1 Physical properties .............................417 9.6.1.1 Particle size distribution ....417 9.6.1.2 Soil reaction .........................420 9.6.1.3 Bulk density and porosity ................................420

xx

Contents 9.6.2

9.7

Chemical characteristics ....................421 9.6.2.1 Humus content and composition .........................421 9.6.2.2 Nitrogen content .................424 9.6.3 Clay mineralogy .................................424 9.6.4 Charge characteristics ........................428 Land use and evaluation ................................432 9.7.1 Evaluation of analytical properties ............................................432 9.7.2 Signiicance of basic soil properties ............................................432 9.7.3 Agricultural operations .....................433 9.7.3.1 Estate crops ..........................434

References and Additional Readings .......................447 Index ...............................................................................475

Preface In this book, soils formed under a tropical climate, and in particular in Indonesia, are illustrated and described. Some U.S. scientists believed that there were no such tropical soils, and that the term tropical soil was just a myth. These soils were allegedly not different from their taxonomic counterparts, if any, in the United States, which in this author’s opinion is far from true. For example, oxisols are soils conined only to tropical areas. In the tropical, humid regions of Indonesia, these soils may look similar to some of the soils in the southern region of the United States. They may have some features in common (for example, high clay content, high water-holding capacity, and not too much difference in the red colors). However, they are, in fact, very different in many other aspects, and they behave differently—biologically, physically, and chemically. For example, Indonesian oxisols originate from intermediate to basic volcanic ash of quaternary eruptions. The soils exhibit properties relecting more the effect of short-range order, semicrystalline or amorphous minerals than those of crystalline clays. The time period for soil genesis (from ash to soils), compounded by a humid, tropical condition, was apparently too short for

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Preface

the proper formation of crystalline clays. Though the clay content may amount to 80 to 90%, the soils possess a very stable and strong structure, allowing them to be cultivated during heavy rains. These features are completely different from U.S. soils in the southern region. The closest comparison is perhaps with the Davidson soil. However, this soil exhibits properties showing the dominant role of crystalline clays, though short-rangeorder minerals may have affected them somewhat. The soils are also often sticky and plastic when wet and very hard when dry. According to the U.S. Soil Taxonomy, these soils are ultisol, formed in material weathered from diorite, mica schists, or basaltic rocks. None of the oxisols (Eutrorthox or Haplorthox) in Puerto Rico or the Virgin Islands appear to be similar to the tropical soils in Indonesia. The oxisols in Puerto Rico are allegedly marginal lands, suffering from drought even during short dry periods, whereas those in Indonesia are excellent agricultural lands, as will be discussed in Chapter 6. The parent materials of the oxisols in Puerto Rico have also been reported as tertiary limestone, which in Indonesia would have formed terra rossa or red Mediterranean soils and alisols. Perhaps oxisols in Hawaii may compare more favorably in some aspects, but the U.S. Soil Taxonomy states that they are not extensive and can be similar only to oxisols from basic rocks that are found in South America and Africa. The author also wishes to show that a tropical climate is not necessarily hot and humid, but may vary from hot and humid to cool and arctic cold with elevation, when going up from the lowlands to the top of the mountains. These differences in climate, which bring about

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xxiii

altitudinal variations in vegetation, have a pronounced effect on soil formation. The changes in geomorphology, and especially those in climate and vegetation, with elevations above sea level are particularly noticed to have produced altitudinal variations in soil formation, yielding zones of different soils. In addition, this book addresses the following issue. During Dutch colonial time, Dutch scientists collected an abundant amount of research materials, most of which were written in Dutch and published in local papers. They are now buried in a maze of library references in Indonesia and are very dificult to ind. Though most of the materials may be considered old, they are very valuable and still relevant in today’s scientiic standards. This information will be lost forever to most, if not all, of the new generation of Indonesian and international scientists who do not read the Dutch language. Because of this, the author has retrieved most of the old information and is making it accessible in this book in a somewhat revised version, with a more modern lavor added to the old concepts. The genesis, properties, classiication, and land use of the soils are major topics of discussion in this book. The basic materials originated from the author’s experience as a native of Indonesia and from his research as professor and head of the Department of Soil Science, Bogor University of Agriculture (better known today as IPB for Institut Pertanian Bogor), Indonesia, from 1957 to 1967. After accepting a position in 1968 as professor of Soil Science and Agronomy at the University of Georgia, Athens, the author’s activities in soil research and as the Agronomy Club soil judging coach for more than

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Preface

10 years provided him with excellent opportunities for studying and making valuable comparisons between U.S. and Indonesian soils. Additional information was collected during teaching and research assignments (1995 to present) as visiting professor at several research institutes and universities in Indonesia, including Bogor Research Institute for Estate Crops; Soil Research Institute, Bogor; University of Andalas, Padang; and the University of North Sumatra, Medan. The nine chapters in this book can perhaps be divided into two parts. The irst part includes Chapters 1 through 5, covering the development of soil science in Indonesia, the geography and geomorphology of the archipelago, climate, vegetation, mineralization, and humiication processes as factors of soil formation in Indonesia. The second part includes Chapters 6 through 9, and examines the major soils in Indonesia and their genesis, properties, taxonomy, land use, and evaluation. The latter also addresses the cultivation of local farm, estate, and industrial crops, which differ in types and varieties from the lowland to highland regions. For example, rubber and oil palm, restricted to growing in the lowlands, are replaced by tea and coffee in the highlands. The vegetable crops of the mountains are more temperate region crops, whereas bananas of the types offered in U.S. supermarkets, growing best in the lowlands, tend to also be replaced by a mountain variety in the highlands of Indonesia. All these and more will be discussed in the respective sections of the book. The soils are discussed according to the following arrangement: (1) soils of the lowlands (for example, oxisols, ultisols, lowland alisols, or red Mediterranean

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xxv

soils and vertisols) and histosols (tropical peat soils); (2) soils of the upland (for example, podzolic latosols and inceptisols or brown forest soils); (3) soils of the mountains (such as highland or mountain alisols, brown podzolic soils, and spodosols); and (4) andosols (soils in the mountains as well as in the lowlands). Though the names of soil orders in the present U.S. Soil Taxonomy are used in the titles, many do not adequately represent the Indonesian soils in question. Hence, the names of soils from the World Reference Base for Soil Resources (WRB), Food and Agriculture Organization of the United Nations (FAO-UN), Australian and Canadian soil classiication systems, and the older (1948) U.S. Soil Taxonomy are also stated, which in the author’s opinion often represent more closely the particular soils in Indonesia.

The Chapters Chapter 1 covers the development of soil science in Indonesia, from the pre-World War II period with a dominating Dutch inluence, to the post-World War II period, where the American system was gaining importance, especially through cooperative educational projects with the University of Kentucky, Lexington, and the Midwestern Universities Consortium, respectively, under the sponsorship of the U.S. Agency for International Development (USAID). Most of the older but important work by Dutch scientists in pedology, soil survey, soil fertility, plant nutrition, land use, and conservation are included. The establishment of higher education and

xxvi

Preface

the dawn of new experiment stations are examined in view of advancing soil science in Indonesia. Chapter 2 examines geography, geomorphology, and other factors of importance as parent materials for soil formation in Indonesia. The signiicance of dividing the archipelago into the Sunda and Sahul shelves in between the Wallacea is explained, and major geomorphological features are provided for the islands of Java, Sumatra, Kalimantan, Sulawesi, Moluccas, the lesser Sunda islands, and Papua (formerly West Irian). Chapter 3 discusses the climate in Indonesia. The concepts of equatorial, tropical, and monsoon climates are deined, and local use is examined for considering the west monsoon and east monsoon as the rainy and dry seasons, respectively. The relevance between Mohr’s climatic system and that of Schmidt and Ferguson are compared. The signiicance of a monsoon and tropical climate is addressed, and their altitudinal divisions into lowland, upland, and mountain-land zones are determined and evaluated as factors in soil formation. Chapter 4 describes the vegetation in Indonesia. The concept of climax vegetation is deined, and the types present in Indonesia are discussed (for example, tropical rain forests, monsoon, and savannah forests). The division of the archipelago by Van Steenis into three vegetation provinces is addressed. Altitudinal vegetation zones are identiied due to changing climate with elevation above sea level (for example, coastal lora, rain forests, mountain rain forests, cloud-belt forests, and subalpine vegetation). Limits for cloud belts and timberline are given.

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xxvii

Chapter 5 explains soil formation and classiication in Indonesia. The soil formation factors and processes are discussed and the inluence of climatic variations and different parent materials are addressed. The role of precipitation/evapotranspiration ratios in weathering intensity is presented. The system of soil classiication in Indonesia is described. Chapter 6 examines soils in the lowlands, the parent materials, climate, morphology, analytical features, classiication, land use, and evaluation. These soils include oxisols, ultisols, lowland alisols, vertisols, and histosols: • Oxisols are the former latosols with excellent physical properties regardless of their extremely high clay content. They have been formed mainly in the humid tropics from andesitic volcanic tuff. • Ultisols, formerly called red-yellow podzolic soils, are soils with lower-based status and are more acidic in reactions than the oxisols. They have been formed from more acidic parent materials (such as dacitic and liparitic tuffs) and are rich in quartz. • Lowland alisols are the soils formed by laterization in the limestone areas. The name alisol was chosen as the closest placement in the U.S. Soil Taxonomy only and does not exactly describe the soils properly. These soils are more related to the red oxisols and ultisols and are known as red-yellow Mediterranean or terra rossa soils. • Vertisols are often found as a toposequence or, in close association with the lowland alisols, at locations with more impeded drainage conditions.

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Preface

Sugarcane is one of the major crops grown on the vertisols of Indonesia. • Histosols are mainly peat soils, called tropical peat by FAO soil scientists. They were not expected to exist in the warm humid tropics, but in 1895, Koorders reported the presence of extensive peat areas in Sumatra. These soils have now been found extensively in the coastal regions of Sumatra, Kalimantan, and Papua. Chapter 7 features the major soils in the uplands of Indonesia (for example, podzolic latosols and brown forest soils). The latter is identiied in the U.S. Soil Taxonomy as inceptisols. This name is also selected in this book, because it is the only order’s name in the U.S. Soil Taxonomy that can be used. The soils, in fact, do not really represent young soils as the name implies. The brown forest soils or inceptisols of Indonesia are fertile soils, and due to their formation in the cooler uplands, both tropical and temperate region crops can be grown on these soils. They are also the soils on which cloves are cultivated, one of the major spices that, in its early history, made Indonesia renowned as the Spice Islands. Chapter 8 discusses the major soils in the mountains of Indonesia (for example, highland or mountain alisols, brown podzolic soils, and podzols [spodosols], respectively). The name highland alisols is used in this chapter to differentiate them from the lowland alisols discussed in Chapter 6. These highland alisols occur in zones, where cool and humid conditions prevail. The soils appear more like the gray wooded or the graybrown podzolic soils of the Canadian and old U.S.

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xxix

systems, or the luvisols of the FAO-UN system. These soils support a variety of temperate region crops, including wheat and grapes. Lowland types of bananas tend to be replaced by mountain bananas. The cool climate also encourages development of dairy farming. The brown podzolic soils are located in between the highland alisols and the spodosols. They are considered by some as podzols in the initial stages. The spodosols are soils generally present only in the mountains of Indonesia, where the climate and vegetation are favorable for podzolization processes. They are called podzols in the old U.S. classiication and the FAO-UN systems, and this name is still used today in Europe. Podzols have also been discovered by the Dutch in the lowlands of Bangka, but these are considered as exceptions and their occurrence is apparently limited to very small areas. Chapter 9 offers an overview of the andosols, which can be found both in the mountains as well as in the uplands and lowlands of Indonesia. These are the andisols in the new U.S. Soil Taxonomy. In Indonesia, they are frequently confused for brown forest soils. Andosols are perhaps the most fertile soils of the Indonesian archipelago. A variety of crops are grown on andosols, and the best tea and coffee plantations are found on andosols. Kim Howard Tan The University of Georgia Athens, Georgia

Acknowledgments The author would like to acknowledge and thank many people and institutions for their assistance, reviews, comments, and contributions. Thanks are due in these respects to H.F. Massey, former Associate Dean for International Programs, University of Kentucky, Lexington. He was a visiting professor at IPB, Bogor, Indonesia, serving in the 1960s also as acting chief of the University of Kentucky Contract Team at IPB. Thanks are also extended to Roy Sigafus of the University of Kentucky Contract Team and visiting professor at IPB, Bogor, in the 1960s, for reading the early drafts of this manuscript. Grateful appreciation is extended to Irsal Las, Director of the Indonesian Center for Agricultural Land Resources Research and Development, and Fahmuddin Agus, former Director of the Soil Research Institute, Bogor, Indonesia, for their cooperation and courtesy in providing the latest version of the Soil Map of Indonesia. Thanks are also due to Didiek H. Goenadi, Director of the Institute of Biotechnology for Estate Crops, Bogor, Indonesia; Dian Fiantis, Pedologist, Ir. Datuk R. Imbang, Soil Taxonomist Ir. Burhanuddin, SU, former Associate Dean, Faculty of Agriculture, University of Andalas, Padang; and to Abu Dardak, former Director,

xxxii

Acknowledgments

Graduate School, University of North Sumatra, Medan, Indonesia, for their valuable contributions and for collecting several of the data. The assistance of O. Iskandar, former chairman of the Department of Soil Science, Institut Pertanian Bogor, and that of the Forestry Service, Badan Planologi Kehutanan Indonesia, are hereby also gratefully acknowledged for crop yield data and the use of a vegetation map, respectively. Finally, my grateful thanks are extended to Januar Darmawan of P.T. Cengkeh Zanzibar for providing some of the pictures, to H. Hartawan, serving as a professional photographer, and last but not least to my wife Yelli and my son Budi, for their understanding, encouragement, and assistance in writing this book.

chapter one

The development of soil science in Indonesia For hundreds of years people have looked upon the earth as the source of their food and iber supply and as the bearer of minerals and metals useful for their wellbeing. But not until the nineteenth century have soils been studied on a scientiic basis. This is also true for Indonesia, where soil science can be considered much younger than in many other countries. In its development, two periods can be distinguished in Indonesia—the pre-World War II period with the dominating Dutch inluence and the post-World War II period, during which the Food and Agriculture Organization of the United Nations (FAO-UN) and U.S. Department of Agriculture (USDA) systems were gaining importance, forming the basis for the development of the present soil science with a strong imprint of a homegrown Indonesian identity.





Soils in the Humid Tropics and Monsoon Region of Indonesia

.

The pre-World War II period

Soil science during this period started to develop during the glory of the Dutch colonial time from approximately the nineteenth through the twentieth centuries. The establishment of the Dutch empire dated back to early in 1602, when after a decisive battle with the Portuguese, the VOC, Vereenigde Oost Indische Compagnie (for United East India Company), was created by the Dutch in Bantam, Java. The VOC, in fact, was a trading post with its main interest only in gaining the monopoly of the lucrative spice business—pepper from Sumatra, and cloves, nutmeg, and mace from the Moluccas. It was supposed to be a trade and collection center for spices, and its location near a major sea route, the Sunda Strait, has proven to be of extreme advantage for extending Dutch domination over the archipelago. In 1918 the Dutch appointed Jan Pieterszoon Coen governor general, who, after defeating the British, set up headquarters in the small port then known as Jacatra, but renamed Batavia by Coen in 1918. Since then until the middle of the twentieth century, the Dutch gained power in the Indonesian archipelago, which was named the Netherlands East Indies. Regardless of what many people thought about colonialism, the eficiency of the Dutch rule, as compared to any other European colonial powers, was unsurpassed. The presence and availability of spices in the Moluccas, and the great potential of Java and Sumatra for development of tea, rubber, and coffee plantations have been part of the reasons for the relatively long duration of a Dutch empire in Southeast Asia. Perhaps only

Chapter one: Soil Science in Indonesia



the British colony, the former British India, bore some resemblance. Hence, the Netherlands East Indies can be regarded as the best-managed territory among the many Western colonies in Asia, Africa, and other parts of the world. It was late in the nineteenth century when the Dutch colonial time started to peak, culminating during the years 1920 to 1942, that interest in agricultural sciences and especially soil science got a start. The soils in Indonesia were studied primarily by Dutch scientists, familiar with agricultural conditions in temperate region zones. Soon, it became apparent that these experiences, and in particular those imported from the Netherlands, were not appropriate for applications in situations such as that in Indonesia, if and when not modiied appropriately. The need for better scientiic soil investigations was stimulated by the necessity to furnish more data, primarily for the thriving Dutch agricultural enterprises or plantations. Several experiment stations were established for the investigation of major estate crops, where overseas experiences could be thoroughly tested and modiied, and local systems could be developed. These experiment stations were usually located in close proximity to the plantations where the particular estate crops were grown. For instance, a Research Institute for Estate Crops was established in Medan, Sumatra, with a Deli Tobacco Experiment Station, serving the lucrative tobacco plantations located in Deli on the foot of the Sibayak Mountain. In 1916 a Rubber Experiment Station was created, formerly known under the name AVROS, for Algemene Vereeniging voor Rubber Onderzoek ter Oostkust van Sumatra, serving the vast rubber plantations



Soils in the Humid Tropics and Monsoon Region of Indonesia

on the east coast of Sumatra. Other experiment stations were created on the island of Java. For example, a Center for Research of Estate Crops, called CPV (for Centrale Proefstations Vereeniging), was established in 1890 in Bogor, close to the best tea plantations in the mountain range of West Java. A Sugar Cane Research Station in Pasuruan, and a Coffee Research Station in Jember were established in East Java, where most of the sugarcane and coffee plantations were located, because of favorable climatic conditions for growing sugarcane and coffee crops. The attention was focused irst on soil fertility and crop production (Ackermann, 1899/1900; Van Bijlert, 1903; Fromberg, 1858/1859; Tromp de Haas, 1897), but gradually more attention was given to the study of morphology and classiication of soils of the various plantations (Arrhenius, 1928; Bokma de Boer, 1907; Booberg, 1928; Brink, 1932; Kobus and Schult, 1903). With the establishment in 1905 of the Soil Research Institute (now called Pusat Penelitian dan Pengembangan Tanah dan Agroklimat or Center of Research and Development of Soils and Agroclimate) at Bogor, Java, Indonesia, soil research went in a new direction under E.C.J. Mohr as the institute’s irst director, placing less emphasis on the cultivation aspects of estate crops. The Soil Research Institute was inluential for the increased attention in pedogenetic research. Mohr’s agrogeological concept in soil science was published in a series of articles from 1909 to 1916, which were modiied during the years 1922 to 1945 (Mohr, 1922, 1944; see also Mohr and Van Baren, 1960). Mohr eventually became regarded by the Dutch soil scientists as the founder of

Chapter one: Soil Science in Indonesia



pre-World War II soil science in Indonesia, in the sense of Justus Von Liebig for promoting Mineral Nutrition of Plants and Dokuchaiev in the development of Pedology. Since then, many new ideas were presented, and beginning in 1930, led by White (1930), a number of new and younger soil scientists focused their attention on studying pedology and practicing soil survey as carried out in the United States. As expected, Mohr and coworkers afforded strong opposition and voiced criticisms against the American System (Shaw, 1933/1934; White, 1930). Nevertheless, soil research in pedology and soil survey continued with greater activity than before, and even the Soil Research Institute at Bogor started in 1930 a soil survey of Java (White, 1931). This was followed by the Geological Institute carrying out survey work in South Sumatra (Idenburg, 1937; Szemian, 1953). In North Sumatra, soil survey was conducted by the Deli Experiment Station of the Deli Tobacco Company, with its headquarters located in Medan, Sumatra, Indonesia. All of these efforts have produced a variety of detailed soil maps (Druif, 1939a,b; Oostingh, 1927, 1928), which were related somewhat to agronomic, pedological, and geological principles. For this pre-World War II period, the results above were deemed as revolutionary achievements in soil work in Indonesia, as pointed out by Edelman (1947) in his excellent review of soil science in Indonesia. As indicated earlier, all of the above efforts in promoting soil science in Indonesia were performed primarily to satisfy the need for growing estate crops at the large Dutch plantations. The need for research in the cultivation of food crops (for example, rice) was satisied at



Soils in the Humid Tropics and Monsoon Region of Indonesia

that time by the establishment of a General Agricultural Research Station at Cimanggu, Bogor. And more recently, a Rice Research Station was established in Sukamandi, West Java. The focus was on crop production and rice breeding experiments. No major efforts in soil research were conducted by this research institute. The need for higher education in this prewar period was met by the establishment in 1928 of a school of Veterinary Sciences at the university level, which the Dutch called Faculteit der Diergeneeskunde (Faculty of Veterinary Medicine), followed 2 years later by the creation of a Faculty of Agricultural Sciences, modeled somewhat from the Agricultural University at Wageningen, the Netherlands. In the early days, both faculties were not doing well in Batavia (now called Jakarta), until they were moved to the present location at Bogor, which will be discussed in Section 1.2.1.

.

The post-World War II period

World War II disrupted the development of soil science in Indonesia. The Japanese army occupied the country until August 15, 1945, when Japan surrendered, which became oficial September 2, 1945. During the Japanese occupation, no scientiic and research activities were allowed, but these activities resumed slowly again after 1945. The period that followed was a period with many changes, some drastic and abrupt, but many also occurring very gradually. Two days after the Japanese surrender, Sukarno, then president of Indonesia, proclaimed the country’s independence, starting a postwar struggle against the returning Dutch regime, until on December

Chapter one: Soil Science in Indonesia



27, 1949, international pressure forced the Dutch to sign an agreement for transfer of sovereignty of the archipelago, except West New Guinea, now called West Papua. Indonesia was to become part of a political Dutch– Indonesian system, modeled somewhat after the British Commonwealth to keep India and Pakistan under the British Crown. However, it created a very tumultuous period with lots of disputes (for example, Indonesia’s inancial indebtedness and Dutch reluctance to transfer power over West New Guinea). In 1956, Indonesia dissolved unilaterally the union with the Netherlands and drastic measures were introduced for coniscating, nationalizing, or liquidating all Dutch assets. This was partly due perhaps to Sukarno’s concept of ultranationalism, bordering on radicalism. Before World War II, the Dutch sentenced him into exile to Bengkulu, Sumatra, for his activity in a too-early independence movement. The latter was presumably a reason for his dislike or hatred of the Dutch regime, as often shown in his rhetoric, and a factor in the decision to take the drastic steps above, forcing all the Dutch people out of Indonesia. It is against this backdrop of events that the development of soil science in Indonesia unfolded in the irst half of the post-World War II period, as will be addressed below. In the beginning, soil survey was continued by several Dutch scientists using the principles of agrogeology, whereas others moved to investigate soils more on pedogenetic principles with a certain bias on the USDA system. For a while, all activities on soil mapping, survey, and other routine soils work seemed to be centered at the Soil Research Institute, where Dames



Soils in the Humid Tropics and Monsoon Region of Indonesia

(1955) published a book on the soils in east and central Java, considered a compilation of the institute’s activities during the period 1942 to 1954. Attempts were later made by Dudal and Supraptohardjo (1957) to change the old soil classiication by adopting the Food and Agriculture Organization of the United Nations (FAOUN) system. Such a change was considered to provide the Soil Research Institute with a better and more uniform soil classiication system (Dudal and Jahja, 1957). On the other hand, scientiic investigations on soil genesis, soil chemistry, the agronomic importance of soil properties, and crop production were apparently left to the discretion of two major universities—the University of Indonesia located at Jakarta and the Gajah Mada University at Yogyakarta.

..

The establishment of higher education

To meet the need of higher education in agriculture, the Faculty of Agriculture and Faculty of Veterinary Science, established during the pre-World War II period, were reopened and moved to Bogor in 1946, as parts of the University of Indonesia. The name Faculties was used, conforming to Dutch and other European systems for universities’ divisions of higher education, and are different from the U.S. term of faculty, referring to professors and members of the University. The two faculties were consolidated under the name of Institute of Higher Education in Agricultural Sciences (Balai Perguruan Tinggi Pertanian). It was at the Faculty of Agriculture at Bogor where most of the soil research was continued at the start of this post-World War II period under the

Chapter one: Soil Science in Indonesia



leadership of Dutch professors. However, due to the growing unfavorable political conditions during the reign of Sukarno, the irst president of Indonesia, many were gradually forced to return to the Netherlands. In 1963, the Faculties of Agriculture and Veterinary Science at Bogor seceded from the University of Indonesia to become the Bogor Institute of Agricultural Sciences, known today in Indonesia as Institut Pertanian Bogor (IPB). This was followed by the establishment of a number of other universities in the various regions of Indonesia that included a Faculty of Agriculture and Soil Science as important divisions in their structural makeup. It was in line with the new Indonesian government policy to have a university, teaching also agriculture, in each of the provinces. Listed below are some of the major universities in this respect with a strong Faculty of Agriculture and soil science department, representing the major islands in Indonesia (for locations see Figure 1.1): Sumatra: University of North Sumatra, Medan; Andalas University, Padang, West Sumatra Java: IPB, Institut Pertanian Bogor, Bogor, West Java; Gajah Mada University, Yogyakarta, Central Java Kalimantan: Lambungmangkurat University, Banjarbaru Sulawesi: University of Hassanudin, Makassar Moluccas: University of Pattimura, Ambon For some time, the IPB served as a lagship university for the education and training of personnel of the other universities.

JAVA

Bogor Yocyakarta

Jakarta

SULAWESL

NUSA TENGGARA

Makassar

. Banjarbaru Banjarmasin

KALIMANTAN

TIMOR

MOLUCCAS Ambon

UALMAHERA

ARU

PAPUA

Figure 1.1 Map of Indonesia showing the major islands where the universities are located.

1:50,000,000

Padang

SUMATRA

Medan

Banda Aceh

0 Soils in the Humid Tropics and Monsoon Region of Indonesia

Chapter one: Soil Science in Indonesia

..



The Kentucky Contract Team (KCT) and Midwestern Universities Consortium for International Activities (MUCIA) projects

In the efforts to replace the Dutch experts, who were forced to repatriate to the Netherlands, and to develop a new system for advancing research and teaching in higher education, the Faculty of Agriculture at Bogor was chosen as the site for a cooperative educational project with the University of Kentucky, Lexington, sponsored by the U.S. Agency for International Development (USAID) under an AID/W-699 contract (Rice, 1968). The faculty’s afiliation, as part of the University of Indonesia, with its close proximity to the Central Government at Jakarta, was considered perhaps one of the reasons for the selection. A team of U.S. scientists, with Olaf S. Asomodt as the irst group leader, was sent in 1958 by the University of Kentucky, which became actively involved in research and higher education at the faculty in Bogor, lasting until 1966. The group, known as the Kentucky Contract Team (KCT), was inluential for sending many young scientists for further education in research and teaching at various universities in the United States. This has produced a great number of Indonesian experts, enough to rapidly ill the vacuum created by the loss of Dutch professors, enabling science and research to go forward. During this period, a fundamental change took place in 1963 when the two Faculties of Agriculture and Veterinary Science were transformed into the IPB. This move was instigated by the Dean of the Faculty of Agriculture, Tojib Hadiwidjaja, assisted by four young members of



Soils in the Humid Tropics and Monsoon Region of Indonesia

his staff, Bachtiar Rifai, Hutasoit, Kampto Utomo, and the author of this book. Hence, all ive can be considered as the founding members of IPB. At that time, four new faculties were created and added to the newly formed IPB: Faculties of Animal Husbandry, Fisheries, and Forestry, and a year later (1964), a Faculty of Agricultural Technology and Mechanization. The cooperative work with U.S. universities was continued with the Midwestern Universities Consortium for International Activities (MUCIA) in 1970 to 1975, which was extended for another 5-year period during 1975 to 1980. This was followed in 1980 to 1985 by a similar educational and research project sponsored by the University of Wisconsin at Madison. Both the MUCIA and University of Wisconsin projects were USAID-sponsored projects. The IPB had these USAIDsponsored projects from 1958 until about 1990, except for the 4-year period from 1966 to 1970. This long-term support and the great size of the initial project with the University of Kentucky had much to do with IPB’s great development to its present size and status. Many of the American-trained people were appointed to national positions, committees, and task forces, in addition to teaching positions at the universities in Indonesia. To further discuss the development of soil science in Indonesia, it is perhaps better to address the issues in a more systematic and chronological way, according to the different ields—pedology, soil survey, soil fertility, and plant nutrition.

Chapter one: Soil Science in Indonesia

..



Pedology

At the Faculty of Agriculture, Bogor, the concept of agrogeology in soil science was revised at irst according to pedological principles, and the soil classiication system adapted to the one more widely used over the world, such as the zonal system as proposed by Thorp and Smith (1949). The irst major contribution in this period was a textbook on soils written by Wisaksono (1953), which was soon followed by a publication by Van Schuylenborgh and Van Rummelen (1955), who presented results of an investigation showing the presence of brown podzolic, gray-brown podzolic, and brown forest soils in the formerly ill-deined “mountain soils.” This was followed by Van Schuylenborgh (1958), who discovered the distribution of soils to change with elevations above sea level. The author suggested the presence of the following zones from the tropical humid lowlands to the cool mountain regions: • 0 to 300 m above sea level, a zone of laterization, forming latosols. • 300 to 600 m above sea level, a zone of laterization + podzolization with red-yellow podzolic soils dominating the region. • 600 to 1000 m above sea level, a zone of podzolization forming acid brown forest soils and graybrown podzolic soils. This concept was improved by Tan (1958) and Tan and Van Schuylenborgh (1959), who claimed that under the inluence of a monsoon climate, the zonal distribution of



Soils in the Humid Tropics and Monsoon Region of Indonesia

soils with altitude would shift to lower or higher elevations depending on changing climates and differences in parent materials. During the following years, series of articles and books were published on the genesis and classiication of soils in Indonesia (Dudal and Supraptohardjo, 1961; Suhadi, 1961; Supraptohardjo, 1961a, 1961b; Tan, 1960, 1963, 1965, 1966; Tan and Van Schuylenborgh, 1961a, 1961b; Wisaksono and Tan, 1964, 1966).

..

Soil survey

As stated in the aforementioned sections, most of the soil survey work was centered at the Soil Research Institute at Bogor, where the old Dutch system was at irst replaced by the FAO-UN soil classiication concept (Dudal and Jahja, 1957; Dudal and Supraptohardjo, 1957), with a strong bias to that of Thorp and Smith (1949). For additional information, reference is made to Dames (1955) and to the report of the Indonesian Standing Committee on Soil and Land Classiication (1963), presented at the Tenth Paciic Science Conference in Hawaii. Several other important efforts to mention were attempts in producing several regional soil maps as listed below and the soil map of the Indonesian Archipelago (Center for Research of Soils and Agroclimate, 2000; Dames, 1955; Soil Research Institute Report, July 1964): 1. A reconnaissance soil map of East-Central Java at a scale of 1:250,000. 2. An exploratory soil map of Java and Madura at a scale of 1:1,000,000.

Chapter one: Soil Science in Indonesia



3. An exploratory soil map of South Sumatra at a scale of 1:1,000,000. 4. A generalized soil map of Indonesia at a scale of 1:2,500,000. 5. An exploratory soil map of Indonesia at a scale of 1:1,000,000. An example of the 2000 version of the exploratory soil map of Indonesia is shown in Figure 1.2. It was provided courtesy of the Indonesian Center for Agricultural Land Resources Research and Development at Bogor. The mapping units have been selected to accommodate the new system of the U.S. Soil Taxonomy.

..

Soil fertility and plant nutrition

Though not all were properly documented, the greater role of the Faculty of Agriculture was also obvious in advancing the science in this ield. The faculty produced its irst dissertation in 1956, reporting results of investigations on the “Dieback Disease” of clove trees (Tojib Hadiwidjaja, 1956), which was followed in the next year by another dissertation on the “Mineral Nutrition of Lowland Rice in Indonesia” (Go, 1957). Van Schuylenborgh and Sarjadi (1958) then published their results on ield experiments with sugarcane, in which nitrogen–phosphorus–potassium (NPK) ratios were used for a balanced fertilizer scheme in growing sugar cane. The use of NPK ratios was also applied in fertilizer applications on lowland rice, which were reported to have resulted in signiicant yield increases (Go and Van Schuylenborgh, 1959), whereas productivity levels

LEGEND

Figure 1.2 Exploratory Soil Map of Indonesia. (Courtesy of Pusat Penelitian Tanah dan Agroklimat, 2000. Atlas Sumberdaya Tanah Eksplorasi, Skala 1:1,000,000, Puslittanak, Bogor, Indonesia.)

AREA SYMBOL SOIL ORDER % KM2 Histosols 132.023 7.01 180.086 9.62 Entisols Inceptisols 724.858 38.51 21.659 1.15 Vertisols 456.702 24.27 Ultisols 141.136 7.50 Oxisols 52.116 2.77 Alfisols Spodosols 21.819 1.16 Mollisols 85.855 4.56 47.950 2.55 Andisols 16.999 0.90 Miscs 1,882.102 100.00 TOTAL

0 100 200 300 400 500 Kilometers

Ministry of Agriculture Agency for Agricultural Research and Development Center for Soil and Agroclimate Research 2000

EXPLORATORY SOIL MAP OF INDONESIA

 Soils in the Humid Tropics and Monsoon Region of Indonesia

Chapter one: Soil Science in Indonesia



of paddy soils were reported earlier by Hauser and Sadikin (1957a, 1957b). With the help of NPK ratios, Tan and Hutagalung (1960) also attempted to increase the yield of Irish potatoes to twofold. These crops were grown only in the mountains of Indonesia. The sugarcane experiment station in East Java reported the effect of urea in the cultivation of sugarcane (Han, 1961), whereas Massey, Kang, and Surjatna (1963) presented a short review on what has been achieved in improving the production of corn as a staple food crop. In 1964, Tan and Massey tried with success using pedological principles to solve site effects on the growth and productive capacity of Pinus merkusii, an indigenous pine species of the pine forest in Sumatra.

..

The dawn of new experiment stations

In the meantime, most Dutch plantations were purchased (nationalized) by the Indonesian government. For the management of the newly formed government estates, a new institute was established, called PPN for Pusat Perkebunan Negara (or Center of Government Plantations). The liquidation of the Dutch estates was also signaling the closing of most of the estate crop research stations. Of the few remaining experiment stations, the most important was the CPV, which after several name changes from Pusat Penelitian Perkebunan Bogor (1990 to 1993), meaning Bogor Research Station Center for Estate Crops, to Pusat Penelitian Bioteknologi Bogor from 1993 to 2002, became what we now know as the Balai Penelitian Bioteknologi Perkebunan (Research Institute of Biotechnology for Estate Crops). The main emphasis



Soils in the Humid Tropics and Monsoon Region of Indonesia

is now on research in biotechnology of estate crops, advancing, among other things, the use of microorganisms in recycling waste from estate crops and inding new methods for using these wastes as alternative energy sources. Results of the institute’s research on development of biodiesel from oil palm waste and bioethanol from sugarcane residue and trash have recently attracted national attention. The conventional and routine experiments on soil fertility and cultivation of estate crops were apparently left as the responsibility of a newly established institute, called Pusat Penelitian dan Pengembangan Perkebunan (Center of Research and Development of Estate Crops). Before its complete departure, the Dutch government still had the opportunity to develop a new rubber research institute in 1948 under the name INIRO (Institut Nederlands Indiesch Rubber Onderzoek), which in 2002 was reorganized by the Indonesian government into a rubber technology research station at Tanjung Morawa, North Sumatra. The old rubber research station AVROS was renamed RISPA (for Research Institute of Sumatra Planters Association) by the Dutch in 1957, and in 1989 it was transformed by Indonesia into an Indonesian Oil Palm Research Center, called Pusat Penelitian Kelapa Sawit. Both of the new institutes are now under the coordination of the Indonesian Research Institute for Estate Crops. To take care of research in farming systems, major food and horticultural crops, animal production, and freshwater, coastal, and marine isheries, an Agency for Agricultural Research and Development (AARD) was established in 1974 by the Indonesian Ministry of

Chapter one: Soil Science in Indonesia



Agriculture. Under its irst director, Gunawan Satari, results of agricultural research in Indonesia, covering the period of 1981 to 1986, were published by the agency in book form: Five Years of Agricultural Research. Its Contribution to Agricultural Development in Indonesia. In 2006, a new center was created, called the Center for Agricultural Land Resources and Development (Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian). It is responsible for coordinating and overseeing the activities of four research stations: the Soil Research Institute, the Peat Soil Research Institute, the Agroclimate Research Institute, and the Agricultural Environment Research Institute.

..

National conferences and scientiic societies

In this post-World War II era, several soil conferences were also held, summarizing progress obtained during the previous consecutive periods. Only some of the major conferences, which had an impact on the development of scientiic societies and advancement of soil science, are mentioned here. At the initiative of the Association of Scientists in Agricultural and Forestry Sciences (Ikatan Sarjana Pertanian dan Kehutanan), a conference was held at Ciawi (near Bogor) in June 1959, where past soil conservation activities in Indonesia were examined, and strategies for future activities were planned. This was followed at the end of 1961 by a irst National Soil Science Conference at Bogor, sponsored by the Soil Research Institute. At this time, attempts were made by the general assembly of the conference

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Soils in the Humid Tropics and Monsoon Region of Indonesia

to establish a Soil Science Society of Indonesia. At the Asian Soil Conference, Jakarta, Indonesia, in July 1972, an extensive bibliography was published by the Central Library for Biology and Agriculture at Bogor, locally known as the Bibliotheca Bogoriensis, in which most of the published reports and scientiic publications on soils and agriculture in Indonesia were listed from 1940 to 1972. The Soil Research Institute at Bogor celebrated its centennial in June 2005 by organizing seminars on past and future activities on soil survey, conservation, and land use and management in Indonesia.

..

Land use and soil conservation

Compared to the other ields of soil science, scientiic activities in soil conservation have apparently attracted relatively little attention. The importance of soil conservation was not considered seriously by most of the people, perhaps because of the unfortunate notion of the presence of inexhaustible land reserves. That such thinking may have disastrous consequences on the country goes without saying. The irregular water supply of most of the rivers and the annual heavy loods are a few examples. Less serious perhaps is the effect of reckless land cultivation by deforestation and burning. For instance, the slash-and-burn (or ladang) system without allowing time for the forest to return created extensive areas of wasteland invaded by Cochon grass or known by the common name alang-alang (Imperata cylindrica). The very irregular water supply of most of the rivers and the annual heavy looding of the countryside were always taken for granted or ignored. In the past, only a

Chapter one: Soil Science in Indonesia



limited number of reports were published addressing the subject. Schophuis (1961a, 1961b) introduced a land management system and tried to apply aerophotogrammetry in land use and water management. Masman Bekti (1959a,b) discussed conservation practices and management of soil water, whereas Supangat (1961) examined the role of vegetation on soil erosion. Sitepu Dieken (1961) addressed animal husbandry or raising cattle and soil erosion. Additional literature from the early days include works by Pramudibjo (1959) and Tedjojuwono (1959). More recently, a regreening and reforestation program was introduced, funded by the National Watershed Development Program of Indonesia (Agus, 2001). Introduced in 1976 for the purpose of conserving natural resources, it was later extended as part of the government’s 5-year (1992 to 1997) development plan in rehabilitation of critical forest lands and 2.6 million ha of privately owned farm lands. Regreening, as deined by Agus (2001), is soil conservation applied on critical lands owned by local farmers, whereas reforestation is replanting of state-owned lands with trees. Critical land is considered land usually covered by Cochon grass (Imperata cylindrica) and is seriously affected by erosion (Huszar, 1998). The area pronounced to be very critical land amounts allegedly to 12.3 million ha (Agus, 2001). To ease annual looding, some efforts by the government have been noticed in 1965 by providing the Jatiluhur multipurpose dam project at Purwakarta, Java, and the creation of a Land Use Bureau. The Jatiluhur dam was built across the Tjitarum River, one of the biggest rivers in Java, which created an artiicial lake of approximately 83 km2. The purpose was not only to



Soils in the Humid Tropics and Monsoon Region of Indonesia

control annual looding, but also to produce hydroelectric power and a steady supply of irrigation water to the 240,000-ha paddy rice ields of the coastal plain and surrounding area north of Purwakarta. The Land Use Bureau was, in a sense, a reactivation of the Dutch Soil Conservation Service. This is followed today by the Siak River project in West Sumatra for similar purposes. It is, in fact, a cooperative project between the West Sumatra and Riau provinces to dam the Siak River that lows into the Strait of Malacca. Perhaps a similar project can be initiated across the Ciliwung River to curb the annual looding of metropolitan Jakarta, where the loods seem to become worse each year. In its effort to produce enough food for the growing population, the route to achieving this goal in Indonesia has not changed from the past to the present. It is still based on clearing the forest and bringing new lands into cultivation. True, there have been many changes in cultivation practices in many areas, as for example better use of fertilizers, eficient applications of pesticides to control pests and diseases, and the use of high-yielding varieties of crops (AARD, 1986). However, these changes, though signiicant, apparently may not have been suficient to stop the clearing of the forests and the cultivation of new lands. This is complicated by continuing the transmigration program, at irst introduced by the Dutch regime primarily to reduce the stress created by the heavy population density in Java and to provide cheap labor for the Dutch plantations in Sumatra and Kalimantan. Under the renewed government transmigration efforts in 1976, many of the people in Java have been moved to sparsely populated areas of Sumatra,

Chapter one: Soil Science in Indonesia



Kalimantan, Papua, and the other islands to increase food production. The settlers were provided with 2 to 5 ha of land, on the average often 2.5 ha, which has to be developed in two stages. In the irst stage, the settlers received government support in the form of packages of material for growing food crops and food to sustain them for at least a year. The second stage was independence. The settlers in Sumatra received a cleared spot for growing food crops, often upland rice, and an additional 1 to 1.5 ha planted with rubber or other tree crops on a grant basis. The settlers in Kalimantan were also provided with a cleared piece of land for growing food crops, and another hectare for hybrid coconut to be cultivated on a cost-recovery basis. This transmigration program has been blamed for accelerating deforestation in Indonesia and for causing violent conlicts between some of the settlers and the indigenous population. After the Asian inancial crisis in August 2000, large-scale transmigration was ended. Many of the new settlements have failed, because the settlers were often city folks, lacking any farming skills, especially those necessary for cultivating new lands. Some of the new settlements were, however, noted to be successful, especially where food crops are combined with growing rubber, a system called rubber agroforestry. Another example of transmigration success is noted by the current author in the settlements on the slope of the Ophir Mountain in West Sumatra on the fertile andosols, where the transmigrants have been successful in growing fruit trees, especially oranges for the markets in the big towns of Padang and Medan.



Soils in the Humid Tropics and Monsoon Region of Indonesia

With the rapid advancement in science and technique at the present time, efforts to increase food production in Indonesia can, in fact, also be achieved by intensifying the production of land already under cultivation (Brady, 1990; Tan, 2000). This is supported by reports of Van den Eelaart (2004) and Andriesse (1988) who indicated that intensiication of paddy-rice cultivation, yielding two harvests annually would produce enough rice to make Indonesia self-suficient in this major food crop, without destroying the forest. Increasing new land areas for cultivation always involves deforestation, and because of increased population pressure, deforestation is clearly noticed today to be slowly moving up the mountain slopes. This increases the hazards of soil degradation and erosion and is also very damaging to the hydrology of the ecosystem and Indonesia’s precious wildlife and biodiversity. The burning of the forest during 1997 to 1998, especially in relation to clearing the coastal peat forest, created disastrous wildires, affecting also neighboring countries. Ash and thick smoke, allegedly carcinogenic, blanketed Brunei, Singapore, Malaysia, and affected lands even as far as Thailand, causing much concern and distress among the people of the respective countries. In Indonesia, the international airport Polonia, Medan, was forced to close. Another example was the heavy loods in 2003, causing again the closing of Polonia Airport at Medan, and paralyzing at the same time part of metropolitan Jakarta, the Indonesian capital. Hard hit was the area surrounding the presidential palace at Jakarta, and the disastrous loods were repeated in 2007 with increasing ferocity. The heavy downpours, bringing huge amounts of water, could not

Chapter one: Soil Science in Indonesia



be sustained by the land, suffering from deforestation on the slopes of the Gedeh-Pangrango and Salak volcanoes in West Java, and on the bare slopes of the Sibayak Mountain in North Sumatra. Unfortunately, the sprawling urbanization has apparently complicated efforts at reforestation and sound watershed management. In the mountain regions of West Java and North Sumatra, local merchants have encouraged clear-cutting the vegetative cover on roadsides and beyond for setting up produce stands, restaurants, and hotels. Afluent people from Jakarta and Medan are making the situation worse by destroying more of the forest on mountainsides for building bungalows, villas, and other summer retreats. Additional evidence for the destruction of the hydrology of the ecosystem includes reports of dangerously lowering the water levels in many lakes. Lake levels in Lake Singkarak, Lake (Danau) Atas, and Lake (Danau) Bawah in the Bukit Barisan Mountain Range of West Sumatra near the town of Bukit Tinggi were reportedly decreased by approximately 50 cm to 10 m, and areas formerly inundated are now drylands at the shores of Lake Atas and Lake Bawah (Tan, 2005).

chapter two

Geomorphology of Indonesia .

Geographical setting of Indonesia

Indonesia is an archipelago and consists of more water than land area. Only 42% is land, which is shared by a group of 3000 islands, situated in the humid tropics and monsoon regions between 6° north and 11° south latitudes and between 95° and 141° east longitudes. The total land area of approximately 1,904,343 km2 is more than 90% located on the ive largest main islands (Table 2.1). The remainder is distributed over the smaller islands, many uninhabited, ranging in size from several square kilometers to mere isolated rocks or coral reefs. The archipelago is affected by two continental masses: Asia in the northern hemisphere and Australia in the southern hemisphere. Dutch geologists and several other scientists believe that friction between the tectonic plates of these two continents has created these folded arcs of islands in Indonesia, with active mountain building, volcanism, and periodic seismic upheavals (Fisher, 1966; van Bemmelen, 1949). Another also widely accepted theory considers the islands as parts 



Soils in the Humid Tropics and Monsoon Region of Indonesia

Table 2.1

Land Distribution of Indonesia Area of Arable Land 2 Area (km ) ×1000 ha Per capita

Total land Java and Madura Sumatra Kalimantan Sulawesi West Papua

1,904,343 132,174 473,606 593,460 189,035 421,951

8374

0.138

Sources: Biro Pusat Statistik Jakarta (1963) and Fisher, C.A. (1966). (With permission.)

of the arc of volcanoes and fault lines, belonging to the Paciic Ring of Fire, circling around the Paciic basin. This chain of islands forms a discontinuous land bridge between the two continents stated above, Asia in the northwest and Australia in the southeast, crisscrossed by three major natural sea routes, the Sunda and Makassar Straits, for passage through the South China Sea to China, and the Malacca Strait, the main thoroughfare to India and the Indian Ocean. Hence, the islands of Indonesia, lying on the fringes of one of these major sea routes and located closest to the Asian continent, have been affected the most by foreign inluence and have beneited immensely from foreign trade. This was also one reason why the Dutch built the VOC (Vereenigde Oost Indische Compagnie [for United East India Company]) in Banten, their irst port of entry, conveniently located next to the Sunda Strait, after the arduous journey through the Indian Ocean. On the other hand, the islands in the eastern part of Indonesia (e.g.,

Chapter two: Geomorphology of Indonesia



Moluccas and Papua) were more isolated and less affected by foreign inluence or commerce. From geological, biological, and ethnological points of view, the archipelago can be distinguished into three divisions: the Sunda Shelf area in the west and the Sahul Shelf area in the east, with an area in between called Wallacea, after the name of a famous natural scientist Alfred Russell Wallace (Lighart, Hövig, and Rinkes, 1926; van Bemmelen, 1949). The Sunda Shelf, covering the islands of Kalimantan, Java, and Sumatra, and the smaller islands Riau, Banka, Belitung, and Singkep, belongs to the inluence sphere of the Asian continent. On the other hand, the Sahul Shelf, consisting of Papua, Aru, and surrounding islands of the Arafura Sea, is inluenced by Australia. The region of Wallacea is considered a transitional zone, where the Sunda Shelf and Sahul Shelf meet or intermingle (Fisher, 1966). It includes the islands of Sulawesi, Bali, Lombok, Flores, Sumbawa, and Timor. This area is separated in the west from the Sunda Shelf by the Wallace line, which runs through the Bali Strait and Macassar Strait north to the Sulu Sea, east of the Philippines. The line separating the Wallacea from the Sahul Shelf in the east is called the Weber line. This imaginary division line runs from the Timor Sea northward through the Banda Sea (west of Buru) and the Moluccas Sea (west of Halmahera). The Sunda Shelf is surrounded by the Circum Sunda Mountain system, which cuts across the trend line of the Australian Mountain system. The Circum Sunda Mountain system consists of two main parts: Its northern part, which also covers the Philippines, belongs to the island chain along the western Paciic, whereas

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

the southern portion forms a part of the great Sunda Mountain system. The latter extends from the southern Moluccas to the Brahmaputra valley in Pakistan (Fisher, 1966; van Bemmelen, 1949). Located in the blue tropical seas, the dark green forested mountains make the islands of Indonesia among the most beautiful in the world.

.

Geomorphology of major islands

The geomorphology of Indonesia shows the presence of areas with striking contrasts. The Sunda Mountain volcanism creates considerable relief. With a total length of about 7000 km, it starts in the east from the Banda islands and stretches westward along Nusa Tenggara, Lombok, Bali, Java, and Sumatra across the Andamans and the Nicobars toward Burma. Here it meets the Himalayan range. The Circum Australian system forms another relief unit in the east, which extends along the central axis of Papua to New Zealand. In addition to the extensive mountain systems, broad plains also occur along the east coast of Sumatra, on the northern coastline of Java, and in Kalimantan. The lowland of Sumatra, located between 0 and 100 m elevation above sea level, is estimated to cover 60% of the total area of Sumatra (Mohr, 1944). Geologically, the archipelago is relatively young (van Bemmelen, 1949). Three-fourths of the land surface is estimated to be covered by sediments and volcanic deposits. Tertiary and quaternary formations are more abundant than pretertiary materials. In order to be able to provide a better picture, it is perhaps necessary to

Chapter two: Geomorphology of Indonesia



treat this subject island by island. However, because a lot of work has been published, it would be almost impossible to cover all the materials in the following pages. Moreover, the purpose is to provide some background information on the geologic materials of importance as parent materials when reading the chapters about soils and soil formation. For those interested in more details about the geology of Indonesia, reference is made to the comprehensive work by van Bemmelen (1949), Brouwer (1922, 1925), Rutten (1927, 1946), and Umbgrove (1938, 1949). In addition to the discussions based on their original investigations, the authors stated above have also compiled almost all the work that has been published by other authors. A complete list is provided in their books for retrieval or tracing back the numerous publications by other geologists. Also worthy of reading is the geological outline of Indonesia by Sigit (1962). Among the islands in Indonesia, Java is probably the best known. For this reason, the major geological features, characteristic for the island of Java, will be considered irst in the sections below. A second well-known island is Sumatra, followed by Kalimantan, Sulawesi, Maluku, Nusa Tenggara, and Papua.

..

Geomorphological features of Java

Java is approximately 1000 km long and 200 km in width at the widest spots in the western and eastern parts of the island, but it is only 120 km wide at the central part. It is the smallest of the three main western islands of the Sunda Shelf. Parallel to its longitudinal axis, a fertile alluvial plain stretches west to east, covering the



Soils in the Humid Tropics and Monsoon Region of Indonesia

northern coast to Semarang (Figure 2.1). East of Semarang is found the hilly lands of Rembang, composed of a series of west–east trending ridges, alternating with alluvial plains. The hills are separated to the north from the Java Sea by a narrow sandy beach with dunes. The lat-topped ridges near Tuban are limestone reefs. From here inland toward the center of Java, the country changes into a hilly region of tertiary marls and limestone. This area is bordered to the south by a quaternary volcanic chain of mountains with intermontane plateaus and basins. This mountain zone, lying within the structural depression or fault line, runs lengthwise from east to west through the entire island, continuing into a series of mountains in Sumatra, known as the Bukit Barisan Mountain range. Further to the south of the volcanic belt, the island of Java is covered, from east to west, by a high range of folded tertiary limestone and sandstone mountains, averaging 400 m in height. In some areas a tropical karst landscape has been formed in this folded limestone region, and the land surface becomes drier and more barren toward the eastern part. Bordering this area to the south, a narrow coastal region exists of upraised coral and riffs of the Indian Ocean. In summary, the landscape of Java is dominated by a series of volcanic domes, towering in the sky over a green tropical rain forest. Most of the volcanoes are still active, and several are more than 3000 m high. For example, the Merapi, a 2958-m-high volcano, located 30 km from Yogyakarta, a city of 1 million people, is reported at this very moment rumbling again, sending out steady lava lows and clouds of black ash. Thousands of farmers were

Jakarta

JAVA SEA

BALI

Figure 2.1 Geomorphology of Java. (Scale: 1:8,000,000.) (From van Bemmelen, R.W. [1949]; Fisher, C.A. [1966]; Sigit, S.I. [1962]; and Rand McNally [1995].)

Mnt Muria Mnt Bogor Tangkuban ang Tuban Salak Gede- Prahu Remb Semarang Rembang Hills MADURA Pangrango Bandung Mnt Mnt Kendeng Hills Surabaya Pengalengan Selamat Merapi Highlands Mnt Wilis Yogyakarta Mnt Mnt Mnt Malang Lawu Ijen Kelud INDIAN OCEAN

Sunda Strait

Mnt Danau

W—E

Chapter two: Geomorphology of Indonesia





Soils in the Humid Tropics and Monsoon Region of Indonesia

reluctantly forced to evacuate their farms and paddy ields, located on the fertile mountain slopes. These volcanoes are the chief sources of soil material in Java, and have intermittently delivered ejecta, varying in types from dacites and andesites to basalts. In West Java, the high volcanic peaks are located close together, forming extensive highlands in the Priangan region (for example, Puncak highland near Bogor, Pengalengan intermontane plateau, and Lembang highland near Bandung). In the past, these clusters of volcanoes created a natural barrier for passage and public transportation. However, in Central and East Java, the volcanoes are more widely spaced, separated from each other by broad passes and valleys. The intermittent eruptions have covered the area in West Java with ash, lava, and lahar of mostly dacito-andesitic origin, whereas those in Central and East Java are mostly of andesito-basaltic composition. Such an intermittent rejuvenation of the soil by the rich volcanic material has created very fertile soils. Together with the presence of abundance of water for irrigation of the sawahs (paddy ields) at the footslope of the mountains and the coastal plains, this high soil fertility has produced adequate rice and other food crops, resulting perhaps in the development of a very dense population in Java. As indicated earlier, to ease the problem of overpopulation, the Dutch colonial government  In geological terms, liparites, rhyolites, and dacites refer to acidic materials that are high in silica (65 to 75%) and relatively low in alkalis. Basalts are basic materials that are low in silica (40 to 50%) and relatively high in elements, such as Fe, Ca, Mg, K, and so forth, whereas andesites are intermediate materials with a composition somewhere in between.

Chapter two: Geomorphology of Indonesia



previously instituted a migration system, transferring many of the most unqualiied people for farming to the then sparsely inhabited islands of Sumatra and Kalimantan. Today this migration policy, continued by the Indonesian government, has apparently created a lot of stress and friction. The new settlers from Java, mostly Muslims, have apparently forced their religion on the indigenous inhabitants, which in many instances has erupted in bloody battles and clashes, as recently reported in Kalimantan. Equally important is the fact that some of the lands provided to the settlers were appropriated by the Indonesian government in terms of eminent domain. This was severely contested by the indigenous folks, who claimed ownership of the land by virtue of possession through their ancestors (tanah adat).

..

Geomorphological features of Sumatra

Sumatra is almost four times as large as Java and is situated west of Java, from 6° N to 6° S, in a northwest to southeast direction. It is 1700 km long, and in the northern part it is 100 to 200 km wide, whereas in the southeast the width of the island is about 350 km. The island’s backbone is the Bukit Barisan Mountain range, stretching from Aceh in the north to the Lampungs in the south, which practically forms a barrier for passage or public transport from east to west. The mountain range divides the island into a broad eastern part and a relatively narrow western part. Several main regional divisions can perhaps be distinguished from north to south. They are the Aceh region in the north; the Tapanuli



Soils in the Humid Tropics and Monsoon Region of Indonesia Sabang

Banda Aceh ACEH

Simeulue

Medan Mnt Strait of Sibayak Malacca Lake Toba TAPANULI Siak River

Nias Kampar River Mnt Ophir Indragiri MENANGKABAU Padang Batang Hari Siberut Bangka Mnt Kerinci

INDIAN OCEAN

Musi River Palembang

Bengkulu

W—E

LAMPUNG

Figure 2.2 Geomorphology of Sumatra. (Scale: 1:12,500,000.) (From van Bemmelen, R.W. [1949]; Fisher, C.A. [1966]; Sigit, S.I. [1962]; and Rand McNally [1995].)

(Batak) plateau in the northeast; the Menangkabau highlands in the midwest; the eastern coastal plains of Riau, Jambi, and Palembang; the Bengkulu mountains in the southwest; and the Lampung lowlands at the southern tip (Figure 2.2). Beginning from the east coast, one can notice a broad hilly alluvial plain, crossed by many big and small rivers that have their origins in the Bukit Barisan hinterlands. This zone is separated from the Strait of Malacca by an

Chapter two: Geomorphology of Indonesia



extensive belt of swamps and peat, which in some places is about 30 km wide. From the Asahan River, draining the Toba Lake in the Batak highlands, to the Batang Hari River in Jambi and the Musi River in the south, where Palembang is located, these rivers have not only deposited alluvial material from the western hinterlands, but have also contributed to the formation of vast expanses of tidal swamps and peat on the coast of the Strait of Malacca. The thickness of the peat deposits was estimated to be more than 50 cm to 1 m in some places. This region of tidal swamps and peat has in the past always been treated as wasteland, useless for agriculture, unhealthy, and noninhabitable with seemingly many unsurmountable obstacles for passage into the interior (Fisher, 1966). With the rapid advancement of soil and environmental science, tidal swamps and peat are now recognized as important parts of the ecosystem. They provide sanctuaries and are the nesting places for many birds and animals. They are at the same time the major breeding grounds for an assortment of marine life (e.g., shrimp, crab, and ish). The area containing the peat deposits is noted at present to be rich in oil and natural gas, and important oil ields have been located near Pekanbaru in the Riau province and south in Palembang on the Musi River. Tin is found in the alluvial sediments of the islands of Bangka, Belitung, and Singkep, and bauxite in Bintan of the Riau province. In addition to the above, Sumatra is known for its coal deposits, such as in Umbilin in the Bukit Tinggi area, and in Bukit Asam in the Benkulu mountains. This is in contrast with Java which has no mineral wealth of signiicance. The zone of alluvial plains, described above, changes inland into a gentle, hilly country with tertiary



Soils in the Humid Tropics and Monsoon Region of Indonesia

formations. Next to this lies the Bukit Barisan Mountain range, which contains a number of high and still active volcanoes. Some of the volcanoes are more than 3000 m high. The Ophir Mountain, near Padang, is 2911 m high, but the highest summit is the peak of Mount Kerinci which is 3800 m high. The slope toward the Indian Ocean is generally steep. With the exceptions of two lowland embayments in the north, a very narrow coastal plain occurs between the foot of the Bukit Barisan mountains and the Indian Ocean. The Bukit Barisan mountains are the inorganic source of all the soil materials in Sumatra (Mohr, 1944; van Bemmelen, 1949). They are pretertiary and tertiary in formation with some quaternary from the most recent eruptions. At the beginning of the neocene period, volcanic eruptions delivered acid to intermediate materials. However, at the start of the quaternary age, the ejecta were more dacitic and andesitic in composition. Between these two periods, the materials erupted were mainly liparitic (rhyolitic) of origin. Near Lake Toba, at the foot of the Sibayak Mountain, in the regions of Bukit Tinggi in the Menangkabau highlands, and in the Bengkulu highlands to the south, the more recent ejecta were dacito-andesitic in composition. They have given rise to the development of more fertile soils than those derived from liparitic volcanic tuffs.

..

Geomorphological features of Kalimantan

Borneo, called Kalimantan in Indonesia, is the secondlargest island in the archipelago. In general, Borneo as a whole is composed of extensive, predominantly

Chapter two: Geomorphology of Indonesia



low-lying alluvial plains, surrounding the interior uplands. A narrow northern strip, made up of Malaysian Sarawak, Brunai, and Sabah, is bordered by the South China Sea. Indonesian Kalimantan is characterized by broad plains, extensive hills, and low mountains. It is still covered by a dense tropical rain forest, and the only passage to the interior is through the rivers. The three largest rivers are notably the Kapuas in the west near Pontianak, the Barito near Banjarmasin in the southeast, and the Mahakam near Samarinda on the east coast. At irst glance, it would appear that a rather deinite system is missing in the physiographic pattern. However, after more careful study of the landmass, a certain trend between the extent of the plains and the mountains can be observed. The main division is formed by the mountain system, running from the Kinibalu Mountain, in Sabah, southward over the Iran and Müller range to the Schwaner mountains in the southwest (Figure 2.3), with a highest summit of only 1800 m. This division line separates the big island Borneo into two sections: a western section and an eastern section. The Sunda landmass penetrates into the western section from the southwest coast of the island like a huge wedge. It is bordered in the east and northeast by the mountain system discussed above. This triangular area, with pretertiary rocks, located between Cape Datuk, Cape Sambar, and the Müller mountains, is considered by van Bemmelen (1949) as the proper continental mass of Kalimantan. For a long period of time, the area has been subjected to processes forming a peneplain.

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

W—E

Mnt Kinibalu

SOUTH CHINA SEA

SABAH BRUNAI

Cape Datuk

SERAWAK

Tarakan

Iran Mnts

Kayan River

Upper Kapuas Mnts

Meratus Mnts

Peat and swamps

Mahakam River Barito River

Muller Mnts Kapuas River Pontianak Schwaner Mnts

Samarinda Balikpapan Strait of Makassar

Cape Sambar Banjarmasin

Pulau Laut

JAVA SEA

Figure 2.3 Geomorphology of Kalimantan. (Scale: 1:12,000,000.) (From van Bemmelen, R.W. [1949]; Fisher, C.A. [1966]; Sigit, S.I. [1962]; and Rand McNally [1995].)

A north–south running mountain system of the Meratus mountains forms another division line. However, this is restricted to the southeastern corner of the island. This mountain system consists of many geologic formations, with crystalline schists and peridotites as the most important minerals.

Chapter two: Geomorphology of Indonesia



The lowland, located between the Schwaner and the Meratus mountains, as a whole, is covered largely by tertiary and quaternary formations of the Barito River basin, and is bordered on its southeast coast by broad areas of swampy lands and peat. Though the peat deposit was estimated to be less thick than that of the Sumatran peat, this area in Kalimantan is thought to exceed the vastness of the peat area in Sumatra. It stretches along the south coast starting from Banjarmasin in the east toward Pontianak in the west and extends into the coastal area of Serawak. Again, it should be emphasized that this belt of tidal swamps and peat is a very important part of the ecosystem. It is the only home of the endangered Proboscis monkey. Like in Sumatra, this area also appears to be rich in oil and natural gas, with major oilields located near Tarakan on the western shores of the island facing the sea of Celebes. Coal has also been mined at Tenggarong, near Samarinda in the surrounding area of the Mahakam River, whereas some diamonds and gold were discovered in the Barito basin.

..

Geomorphological features of Sulawesi

Sulawesi, or known internationally by the name of Celebes, is the third-largest island of the Indonesian archipelago. The island is almost entirely covered by mountains and is surrounded by deep sea basins and troughs. It is peculiar in form, composed of four peninsulas, extending in eastern and southern directions. It looks like the central part is the highest part, tying together the four peninsulas in a spider-like shape (Figure 2.4). Such morphology and striking relief were believed to be the



Soils in the Humid Tropics and Monsoon Region of Indonesia W—E

Manado Tondano

CELEBES SEA

MINAHASA

Molucca Sea

Gorontalo

Gulf (Teluk) of Tomini

Donggala Peleng

Danau Poso TORAJA

Danau Towuti

Latimojong Mnts Majene

Sula Teluk Tolo

Mnt Rantekombolo Teluk Bone

Butung

Mnt Makassar Lompobatang Bonthain Selayar

BANDA SEA FLORES SEA

Figure 2.4 Geomorphology of Sulawesi. (Scale: 1:6,000,000.) (From van Bemmelen, R.W. [1949]; Fisher, C.A. [1966]; Sigit, S.I. [1962]; and Rand McNally [1995].)

results of collisions and frictions between several axes, together with extensive faulting of the continental tectonic plates (Fisher, 1966; van Bemmelen, 1949). A large

Chapter two: Geomorphology of Indonesia



number of lakes have been formed between the maze of valleys and ridges in the central part of the islands (e.g., Lake Poso, Lake Towuti, and Lake Matana). Sulawesi forms a link between the East-Asiatic island chain and the Sunda Mountain system (van Bemmelen, 1949). The continuation with the Philippines is maintained by its northern peninsula, the Minahasa region, and proceeds through the Toraja lands into the southwest arm, which in its southern part shows afinities with the mountains of Java and Sumatra. The eastern arm is considered to be continued in the southeastern peninsula, which connects to the Banda areas. The most important parent materials for soil formation of the island are basic formations (Mohr, 1944). The northern area of the north arm is covered by quaternary volcanoes. Several active volcanoes located in the Minahasa region have intermittently delivered a lot of basic materials, giving rise to fertile soils. These mountains disappear toward the west of this northern peninsula. Here, older formations take their place. For example, in the region of Gorontalo, granites and crystalline schists seem to be of more importance. The central part of the island and the northeastern and southeastern peninsulas are nonvolcanic. The area is covered mostly by old formations, such as plutonic rocks, gneiss, all kinds of schists, graywacke, peridotites, and so forth. The southwestern peninsula can be divided into a northern section and a southern section. The northern section, including the Latimojong mountains and the lake area, shows some similarities with the central part of the island. The southern section is composed of three regions. The western mountains along the west coast



Soils in the Humid Tropics and Monsoon Region of Indonesia

consist of andesites and basalts. The Bone mountains on the east coast consist in the south of andesites, whereas to the north this formation disappears and goes over into a neocene limestone range. The southern point of the peninsula, where Makassar is located, at the shores of the Strait of Makassar, is under the inluence sphere of the Lompobatang volcano (named by Dutch explorers as Piek van Bonthain). This volcano, now considered inactive, at one time delivered basaltic tuffs and conglomerates, giving rise to fertile soils. In summary, it can be stated that the geomorphology of the island is in striking contrast with that of Java, Sumatra, and Kalimantan. The largest part of the island is rugged in terrain with strong relief, and extensive areas of lat coastal plains are conspicuously absent. The most fertile regions with well-established agricultural settlements are present in the Minahasa and Makassar regions. Most of the agricultural operations in the remainder of the island are reported to be slashand-burn or shifting cultivation.

..

Geomorphological features of Maluku

Maluku, called Moluccas in English, is a group of relatively small islands, located between Sulawesi and Papua (West Irian). In the early history of these islands, spices attracted the attention of Spanish, Portuguese, and Dutch seafarers and merchants, and hence, the islands were given the nickname of “Spice Islands.” The biggest island is Halmahera, with an area of approximately 8000 km2, and the next biggest are Ceram and Buru. The best-known island is Ambon, measuring only 800 km2

Chapter two: Geomorphology of Indonesia



in area, whereas the other islands, Banda, Tidore, and Ternate, are smaller in size, with Ternate estimated to be only 65 km2. Many more islands are present within the territory of Maluku, ranging in area from a few square kilometers to just a mere coral reef in the Banda or Ceram seas (see Figure 1.1 and Figure 2.4). Maluku is an area with active volcanism or mountain building, though volcanism on the island of Ambon is at present considered to be dormant. Geologically, it can be divided into a northern part and a southern part by a ridge running from the east arm of Sulawesi to the Birdshead (Vogelkop) in Papua. North Maluku, where Halmahera and Ternate are located, consists of two converging ridges, called the Sangihe and the Ternate systems. The Sangihe system forms the connection between the East-Asiatic islands and Sulawesi, whereas the Ternate system loops eastward to Papua and Melanesia. South Maluku, with the islands Ceram, Ambon, Buru, and Bandaneira, consists of the Banda arcs with their two parallel ridges bordering the Banda Sea in the east. The inner arc is active volcanic area, whereas the outer arc is free of young volcanism. In the following section, only two of the most important islands of Maluku will be considered more closely, namely Ambon and Ceram.

...

Ambon

The city of Ambon, located on the island of Ambon, was next to Batavia in Java, the oldest Dutch settlement in this remote corner of the archipelago. It is the capital of the Maluku province and also the home of the University of Pattimura. The island is composed of



Soils in the Humid Tropics and Monsoon Region of Indonesia

old formations, such as graywacke, sandstone, shale, limestone, schist, and peridotite, which are covered for the greater part by younger, probably tertiary volcanic material. The older formations are found on the surface mostly in the southern peninsula of Leitimer. The younger materials are spread more extensively over the island and consist of materials ranging from andesites and dacites to liparites. Due to their peculiar characteristics, this whole group of parent materials was called Ambonites by van Bemmelen (1949).

...

Ceram

The island of Ceram is according to Mohr (1949) not much different from Ambon. Igneous rocks are also considered to be not important with basalt and granite commonly scarce or absent. Widespread are, again, sedimentary and metamorphic rocks, such as mica schists, graywacke slates, and some Triassic formations. As is the case in Ambon, no active volcanism is present today.

..

Geomorphological features of Nusa Tenggara

Nusa Tenggara, also known as the Lesser Sunda Islands, consists from east to west of the relatively small islands of Timor, Alor, Flores, Sumba, and Sumbawa, with Timor and Flores forming perhaps the two biggest islands. Timor is in close proximity to Australia, separated only by the Timor Sea. The islands Lombok and Bali can be considered linking this island chain with the island Java.

Chapter two: Geomorphology of Indonesia



Geomorphologically, Nusa Tenggara can be distinguished into two different areas. A volcanic area of 1000 km long, including Bali and Lombok, connects the inner Banda arc, running east–west through the island chain, with the mountain systems of Java and Sumatra. A second arc, located more to the southeast, is nonvolcanic and includes Timor and surrounding islands. Coral reefs are present more abundantly, whereas the climate becomes toward the east increasingly drier, quite different from the equatorial humid climate prevalent in Java and Sumatra. The very long and intense dry seasons have resulted in scrub-like vegetation and a savannah or steppe landscape. The parent materials for soil formation may range from quaternary intermediate-acid volcanic materials to neocene formations. Along the coast, mostly young quaternary alluvial coastal plains are found. Bali and Lombok have some similarities with Central and East Java, characterized by fertile volcanic slopes and foothills, bordered by relatively broad plains, though the lowland areas are somewhat smaller in size in Lombok.

..

Geomorphological features of Papua (West Irian)

The big island bordering the Moluccas to the east is known internationally as New Guinea. The whole island is considered a continent by itself and has been shared half by Indonesia and half by Australia. The western part of the island was historically Dutch territory, called West New Guinea at that time, whereas the eastern part is now Papua-New Guinea, a self-governed nation within



Soils in the Humid Tropics and Monsoon Region of Indonesia

the British Commonwealth with close ties with Australia. After the surrender of sovereignty of West New Guinea, Indonesia renamed it Irian Jaya or West Irian. This name has been changed again into Papua by Indonesia following the will of the people. In size, the area of mainland Papua almost equals the size of Borneo. However, the province of Papua in the Indonesian Archipelago includes many surrounding small islands—for example, the islands of Biak (formerly called Schouten Island), Numfoor, and Yapen in the Gulf of Sarera or Geelvink Bay (today also called Teluk Cenderawasih) bordering the Paciic Ocean. To the south are the Kai (or Kei), Tanimbar, and Aru islands in the Arafura Sea, separating them from Australia (Figure 2.5). Most of mainland Papua is still unknown territory. Papua can be distinguished into a western part and an eastern part. The western part is a peninsula, called the Vogelkop or Birdshead, because of its peculiar landform, relecting the head of a bird. It is connected to the mainland in the east by a narrow neck. The Birdshead area has on the north coast an east–west running young volcanic mountain range, called the Arfak Mountains, which consist of andesitic and basaltic formations. A tertiary folded mountain zone runs through the “neck” of the Birdshead southeast into the Owen-Stanley Range, which connects with the Nassau or Oranje mountain ranges. This is a very broad mountain zone with a width estimated at more than 160 km. The mainland shows a number of parallel zones. Starting from the coast of the Paciic Ocean (to the north), a narrow coastal plain stretches more or less east–west.



Chapter two: Geomorphology of Indonesia Waigeo

BIRDSHEAD

PACIFIC OCEAN

Sorong Biak Arfak Mnts Mamberamo River

Ceram

Yapen Teluk Cenderawasih Tariku River

Teluk Berau Fakfak

Van Rees Range

Kei Islands

Tanimbar Islands

Fly River

Aru Islands

Eilanden River

Digul River

Cartensz Idenburg Idenburg River top top Nassau-Oranje Range

Digul-Fly Depression

ARAFURA SEA W—E

Figure 2.5 Geomorphology of Papua. (Scale: 1:12,500,000.) (From van Bemmelen, R.W. [1949]; Fisher, C.A. [1966]; Sigit, S.I. [1962]; and Rand McNally [1995].)

This is bordered inland to the south by a mountain range, known as the Northern Watershed mountains (Mohr, 1944) with granites, chlorites, and crystalline schists as major formations. The Northern Watershed mountains include most probably the Cyclop and the Bougainville mountains (van Bemmelen, 1949). Next to this mountain zone (to the south) is a depression area, known as the Meervlakte or Central Lake Plain. The natural drainage here is provided by the Taritatu (Idenburg) River, meeting the Tariku (Rouffaer) River, to form the

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

Mamberamo or Tarikaikea River, which runs to the north into the Paciic Ocean. To the south of the Central Lake Plain lies a complex mountain system, called earlier the Nassau or Oranje Mountain range, running east–west through the main axis of the mainland. The highest parts, the Idenburg top (Puncak Trikora) and the Cartensz top (Puncak Jaya) with summits reaching 4900 m and 5040 m, respectively, are known as the Snow Mountain range with everlasting snow and glaciers on their peaks. To the south of the Snow Mountain range, a broad lowland plain exists, running toward the Torres Strait, which separates Papua from Australia. This area of coastal plain is known as the Digul-Fly depression, named after the Digul and Fly rivers, which contributed to the formation of this extensive coastal region. This low-lying lat area, mostly covered by tidal swamps and peat, extends westward over another important river, the Eilanden River, and beyond. The extent of swamp and peat lands exceeds the size of those in Kalimantan and Sumatra.

chapter three

Climate of Indonesia .

Climate

During the years in the pre- and post-World War II periods, a considerable amount of work was done on qualitative and quantitative investigations of the climate of Indonesia. The Dutch government needed this information for their plantations, and many of the large research stations were adequately equipped with weather stations. Reliable and well-arranged climatological data were compiled and are now available as publications of the Meteorological and Geophysical Institute at Jakarta. For more basic details, reference is made to Teil et al. (1931), Boerma (1931), Braak (1925–1929, 1931, 1939, 1948), Mohr (1944), Schmidt and Ferguson (1951), Schmidt-Ten Hopen and Schmidt (1951), and Mohr and Van Baren (1960). The intention of this text is to review, discuss, and apply the weather information only as a factor in the formation of Indonesian soils. Many types of climates have been used for delineating the climate of Indonesia. The names equatorial and tropical climates have been assigned to characterize the prevailing climate in the archipelago, and the two terms have been applied synonymously by many scientists for reasons explained below. Another type of climate 



Soils in the Humid Tropics and Monsoon Region of Indonesia

applied to often characterize the climate in Indonesia is the monsoon climate, and the Indonesian people commonly relate the west monsoon with the rainy season and the east monsoon with the dry season. This may be true for certain parts but is not necessarily correct for other parts of the archipelago. To alleviate some of the confusion, it is perhaps of importance to deine the three types of climates and discuss to which parts of Indonesia they can be applied.

..

The concepts of equatorial and tropical climates

...

Equatorial climate

The equatorial climate is considered to exist within the equatorial zone, which is usually by convention accepted to lie between 5° N and 5° S (latitudes). The wind pattern associated with the equatorial climate is called the trade wind. In the northeastern hemisphere, the trade wind blows from the northeastern direction to the equator, whereas in the southern hemisphere the wind comes from the southeastern direction. Usually heavily loaded with moisture, evaporated from the Paciic and Indian Oceans, these winds bring a lot of rains, which is the reason for the presence of a dense tropical rain forest, growing in countries near the equator. Due to its location between 6° N and 11° S, Indonesia may fall within the zone of an equatorial climate. Its northern region may be affected by the northeast trade wind, but the southern region is inluenced by the southeast trade wind. The equator goes across the Bukit Barisan Mountains near

Chapter three: Climate of Indonesia



Bukit Tinggi and stretches eastward across Pontianak, separating the islands of Sumatra and Kalimantan into northern and southern halves. The remainder of the archipelago is mostly in the southern hemisphere. The equatorial climate is generally characterized by high precipitation, as indicated above, and by high temperatures throughout the year. Generally speaking, this is the hot and humid climate that many people associate with the tropics. For example, the towns of Bukit Tinggi and Padang in West Sumatra show a 20-year monthly average temperature of 20°C and 26°C, respectively, which is fairly constant throughout the year. The annual precipitation was recorded to average 2400 mm for Bukit Tinggi and 4500 mm for Padang. The town of Pontianak, which the equator passes right through, as indicated earlier, is characterized by a monthly average temperature of 26°C and an annual precipitation average of 3200 mm. Both temperature and precipitation do not luctuate throughout the year. Nevertheless, towns a little above or below the equator, such as Manado (1° N) in the Minahasa peninsula and Manokwari (1° S) in the Birdshead of Papua, exhibit rainfall patterns with monthly averages of only 100 mm to 130 mm, respectively, for the months of July through October. However, the rainfall in the remaining months of the year is twice that much, with an average of 280 mm/month for Manado and 250 mm/month for Manokwari. Although the months from July to October receive only about half the amounts of rain, it is dificult to say that these months represent a true dry season with 100 mm to 130 mm of rainfall per month.



Soils in the Humid Tropics and Monsoon Region of Indonesia

...

Tropical climate

A tropical climate is deined as the prevailing climate in the tropical zone, which is the zone between the tropic of Cancer (23° N) and the tropic of Capricorn (23° S). Therefore, the tropical zone also covers the equatorial zone, which is perhaps one reason why many scientists confuse an equatorial climate for a tropical climate. The confusion is also aggravated by the absence of general agreement as to what the deinition should be of a tropical climate. As suggested by Köppen (Braak, 1931; Teil et al., 1931), a tropical climate is a climate within the tropical zone that exhibits a monthly temperature that never falls below 18°C. Another concept, which appears to also be widely accepted, is that a tropical climate is characterized by a seasonal rainfall, meaning that it is alternated by a dry season. It should not occur in the form of constant high precipitation throughout the year, as exhibited by the equatorial climate. The temperature should also not be the high temperature characterizing a desert climate (Fisher, 1966). The temperatures of Jakarta and Bandung, in West Java, show a longtime monthly average of 26°C and 22°C, respectively. They are constant at these values throughout the year. The lower temperature for Bandung is due to the location of the town high up on the slope of Mount Tangkuban Prahu. The annual precipitation was recorded over the years to average 1800 mm for Jakarta and 1900 mm for Bandung. Bogor, on the other hand, located 50 km south of Jakarta on the slopes of the Gede-Pangrango Mountains, is characterized by an annual precipitation of 4000 mm. The amount of rainfall appears to not be distributed very evenly throughout the year, with the

Chapter three: Climate of Indonesia



months of June through September receiving less rain than the other months. A monthly average precipitation of 70 mm was reported for Jakarta and 80 mm for Bandung for June through September, whereas the rainfall was 180 mm/month and 200 mm/month in Jakarta and Bandung, respectively, in the other months. The above suggests the presence of a weak dry season in West Java, which tends to become gradually more sharp or pronounced toward Central and East Java. Surabaya, the capital of East Java, receives from July through October an average of only 13 mm/month in contrast to the months of November through June, where an average rainfall is reported of 200 mm/month. The dry season becomes even longer and more drastic in the Lesser Sunda Islands chain because of the inluence sphere of the subarid and desert climate of neighboring Australia.

..

The concept of monsoon climates

...

Concept of monsoons

A monsoon climate is associated with a shifting wind pattern caused by a change in seasons. The name monsoon originated most probably from the Arabic term mausem (meaning season), because in contrast to trade winds, the monsoon wind can shift its path in opposite direction with changing winter and summer seasons of the continents in the northern and southern hemispheres. The system was originally used to characterize the climate in India. The winter season on the Asian continent creates a high-pressure condition, forcing the wind to blow south to the low-pressure region caused



Soils in the Humid Tropics and Monsoon Region of Indonesia

by the summer in the southern hemisphere. This results in a dry season for countries in the northern hemisphere (for example, India). When the winter season changes in the northern hemisphere into summertime, it is then winter in the southern hemisphere, and this change forces the wind to shift its course into a northern direction. It is then the rainy season in India, which generally occurs from June to September. Before entering the Indian subcontinent, the wind has picked up a lot of moisture from the Indian Ocean and brings to the country not only water but also relief from the intense heat. Attempts have been made to apply this concept of a monsoon for explaining the variety of climatic types present in many parts of the world, because four monsoon systems have recently been deined and recognized. They are the North American Monsoon, Northeast (Asian) Monsoon, Southwest Summer Monsoon, and Southeast Asian or Indian Ocean Monsoon. These attempts in a global application of the monsoon concept make the problem even more confusing. For instance, many people have not expected North America to be affected by a monsoon, as it is still hard to believe in the North American Monsoon being the weather maker of the United States. It is true that a highpressure system is created during wintertime above the arctic region of Canada, but no information is available that this will create a wind system blowing toward a low-pressure system developed in the summertime over another landmass located in the opposite direction. The only continent in this respect is Argentina, far away in the southern hemisphere. It is summertime in

Chapter three: Climate of Indonesia



Argentina when winter occurs in the United States, and vice versa. The general idea is that the prime weather maker in the United States is a complex system of low and high pressures, developed in the air because of changes in temperatures of the land surface, atmosphere, and water in lakes and oceans. These pressure systems are apparently affected by the Paciic Ocean in the west and the Gulf of Mexico and Atlantic Ocean in the east. Low-pressure systems, assigned the symbol L on weather maps, usually develop over regions of the Paciic Ocean due to the evaporation of large amounts of water that rise into the air. These then are the alleged tropical monsoon systems, a name that U.S. weather forecasters often used for low-pressure systems that develop above the Paciic Ocean. They are usually carried eastward by the predominantly westerly wind in the United States. Only in a few cases are low-pressure systems coming from the Atlantic Ocean, but due to the prevailing jet stream from west to east, their effect is felt only on the eastern seaboard and is seldom extended to affect the weather pattern of the Western, Southwestern, Northwestern, and Midwestern States. Depending on the conditions, low-pressure systems are the rain makers or they may just izzle out. High-pressure systems, developed by cooling conditions, are generally associated with dry air and are assigned the symbol H. Where high-pressure systems are present, the area usually has nice, clear, and sunny weather. These high pressures may stall or block the movement of the low-pressure systems. At these locations, the low-pressure system may unload its cargo of moisture in the form of some kind of precipitation.



Soils in the Humid Tropics and Monsoon Region of Indonesia

However, the high-pressure systems can also be pushed away by the low-pressure systems toward the Atlantic Ocean. If they move over the Bermuda islands, they are often called the Bermuda highs. In addition to the pressure systems discussed above, the weather of the United States is affected by systems of cool and warm fronts. These fronts are also considered important weather makers of the United States. Fronts have been deined as frontal borders of large air masses moved by wind action. Cold fronts are usually caused by the arctic air masses of Canada, and their movement is mainly southward. On the other hand, warm fronts move north and northeast, because they originate primarily from the warm waters of the Gulf of Mexico, and hence, the air mass behind this front is moist and warm. When the warm front collides with the cold front, the warm and moist air slides over the denser cold air mass to a higher elevation. On the other hand, when the cold front pushes against the warm front, it causes the warm and moist air to rise to a higher elevation in the air, where it may condense into water drops, ice, or snow. The warm front, when active, can also feed a low-pressure system with a lot of moisture and energy. In all these cases, these actions may result in some kind of precipitation, often accompanied by violent weather. Now that we know a little bit more about monsoon, low- and high-pressure systems affecting the climates of Asia and North America, respectively, it is up to you, the reader, to make your own judgment about the correctness of the use of North American Monsoon as the weather maker in the United States.

Chapter three: Climate of Indonesia

...



West and east monsoons in Indonesia

The system of monsoon winds, discussed above, was later extended to characterize the climate of countries in Southeast Asia where similar wind patterns as in India are present. The climate of Indonesia, for instance, is considered by many people to be dictated by monsoon winds, but a number of scientists disagree about this. To consider the climate of Indonesia as monsoonal only may not be entirely correct. My opinion is that the climate of the archipelago shows features of an equatorial, a tropical, and a monsoon climate, depending upon the speciic location within the borders of the country. Large areas of Sumatra, Kalimantan, and Papua are affected more by trade winds than by the monsoon. However, the islands outside the latitudes of 5° N and S may indeed feel more substantially the effect of the monsoon system (for example, Java, Bali, Lombok, and especially east on the Lesser Sunda Islands). Because Indonesia lies within the inluence spheres of Asia in the northwest and Australia in the southeast, the monsoon system is now controlled more by the conditions of these two continents. During wintertime, the high pressure, created above the Asian continent, forces the wind to blow to the southeast where a low pressure is formed by the summer in Australia (December to February). This is usually referred to as the west-monsoon, and the associated northwesterly wind, after crossing the South China Sea, brings the rainy season in Kalimantan and Sulawesi. It is also the cause for the rainy season in the Lesser Sunda Islands. An average rainfall of 270 mm/month was recorded in Kupang, Timor, for the months of October through March, in contrast to

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

the 6-month dry season from April through September, which registered only 16 mm of rain per month. When wintertime arrives in Australia, the monsoon reverses direction and blows to the low-pressure area in the northwest, created by the summertime in Asia. The southeasterly wind, from the Australian high-pressure system, is called the east-monsoon. This system comes from the subarid and desert regions of Australia and consists of dry air. When this wind crosses the Timor Sea, it has not had the chance to pick up enough moisture and is the reason for bringing the dry season in the Lesser Sunda Islands. However, after passing the Banda Sea, the east monsoon has picked up enough moisture from the sea, which brings a lot of rain to Ambon, Menado, and Manokwari. From the discussion above, it seems that a longitudinal variation exists in the monsoon over the archipelago. In other words, when the western part of Indonesia has its rainy season, the Moluccas in the east have their dry season, and vice versa. The rainy season in this eastern part is due to the east monsoon, but only the islands located within the equatorial zone in the east (Ambon and other islands in the Moluccas) will be affected. For Java, Madura, and the Lesser Sunda Islands, located to the south of 5° S (latitude), the east monsoon creates the dry season. This is especially true for the eastern part of this island chain, where long and sharp dry seasons are the norms for the months of April through September. This is supported by evidence obtained from extensive studies on the geographical distribution of the lora in Indonesia in correlation with the climate. The results seem to indicate that only certain parts of

Chapter three: Climate of Indonesia



the archipelago, and in particular the Lesser Sunda Islands in southeastern Indonesia, are characterized by a typical monsoon vegetation (Endert, 1946; Van Steenis, 1948), whereas most of the western parts are covered by a tropical rain forest. Because a climax vegetation is often considered as an expression of the prevailing climatic condition, many scientists believe that the presence of a monsoon lora should be accepted as an indication for the presence of the monsoon climate in the Lesser Sunda Islands, as we should accept the distribution of the rain forest in Sumatra and Kalimantan as the product of a constantly warm and humid equatorial or tropical climate. However, many people remain unconvinced and are of the opinion that the length of the dry and wet seasons is more important for a better delineation of a monsoon, tropical, or equatorial climate.

.

Climatic divisions based on length of dry and wet seasons

In order to better characterize a monsoon climate from equatorial and tropical climates, attempts were made by several Dutch scientists to develop limits of dry and wet seasons (Mohr, 1944; Schmidt and Ferguson, 1951). Others have tried to determine the climax vegetation in various regions of Indonesia (Endert, 1946; Van Steenis, 1948), whereas I have examined the usefulness of Köppen’s climatic system in the classiication of Indonesia’s climate. The data in Table 3.1 summarize the combined results of the above efforts.



Soils in the Humid Tropics and Monsoon Region of Indonesia

Table 3.1 Number of Dry and Wet Months for Classifying Climate and Vegetation Cover in Indonesia Mohr (1944) Number of Wet and Dry Months Climatic Class

I. Constantly Wet

Endert (1946) Köppen

Dry Months Wet Months >100 mm 100 mm a month, the amount of water received by the soil exceeds the amount evaporated, and the months characterized by >100 mm of rainfall are called wet months, as indicated earlier. The excess water leaches the pedon, whereas a large part is available for uptake by growing plants. This is the climate that will sustain a tropical rain forest (Endert, 1946; Van



Soils in the Humid Tropics and Monsoon Region of Indonesia

Steenis, 1948). A short dry season with a monthly rainfall of ≤60 mm, such as in a group II climate, is considered not to be harmful and can still support the growth of a lush tropical rain forest. On the other hand, at long dry periods of 3 to 5 months with a precipitation of 100 mm/month)

(3.1)

By using the quotient, Q, Schmidt and Ferguson divided the climate in Indonesia into eight types of climates, which they presented in a triangular diagram. There are, in fact, several climatic triangle versions present, as shown in Figure 3.1. Mohr et al. (1972) originally used a semitriangular diagram for his divisions of the ive climate groups. In this text,



Soils in the Humid Tropics and Monsoon Region of Indonesia

12

0 70

10 H

% 0 30

9

%

G

8

7 16

%

F

7

5

Q

E

%

of

6

0 10

s ue

l Va

Average Number of Dry Months

11

60

D

%

4

3 4.

B

2 1

%

1 A

1

%

3

C

3

0

3 3.

0

%

2 3 4 5 6 7 8 9 10 11 12 Average Number of Wet Months

Figure 3.1 Climatic system of Schmidt and Ferguson. (From Schmidt, F.H. and Ferguson, J.H.A. [1951]; Mohr, E.C.J. [1944]; and Mohr, E.C.J., Van Baren, F.A., and Van Schuylenborgh, J. [1972].)

the rainfall data of Schmidt and Ferguson (1951) and those of Mohr et al. (1972) were used to calculate the Q values. The calculated values are then converted into percentages by multiplying by 100%, used and integrated into the diagram of Schmidt and Ferguson as shown in Figure 3.1.

Chapter three: Climate of Indonesia



The smaller the ratio or quotient, Q, the wetter will be the climatic conditions, whereas the larger the value of Q, the longer will be the dry season. At Q = 100%, the climate is characterized by a 6-month dry period. Values of Q above 100% indicate that the dry season becomes longer and longer. At Q = 700%, the dry season is 10.5 months, which fortunately does not exist in Indonesia. Most parts of the archipelago perhaps are characterized by types A and B climates, especially the whole western region of Indonesia. Types C and D typify the climates of the monsoon regions of Central and East Java and other regions with a similar pattern of sharp dry seasons, whereas types E and F are found only in limited areas exhibiting the very sharp and long dry seasons as prevailing in the eastern part of the Nusa Tenggara Island chain. Types G and H are practically absent, as indicated above. They have been observed perhaps only over a very small area, such as, for example, in the Palu valley of Sulawesi. Though this system seems to be generally accepted by the forest service in Indonesia, many soil scientists have viewed it as not being an exact climatic system. Because it is solely based on rainfall, which is just one factor determining the climate, the opinion exists that the system of Schmidt and Ferguson was just a mere division of rainfall types.

.

Altitudinal variations in climate

As discussed earlier, Indonesia is covered by extensive mountain ranges, with mountains reaching summits sometimes over 3000 m high. On account of the contrast



Soils in the Humid Tropics and Monsoon Region of Indonesia

in relief formed by the mountains, climatic changes with altitudes above sea level are expected to occur. Altitudinal zones develop due to changes in rainfall pattern, relative humidity, temperature, and vegetation cover.

..

Variations in rainfall patterns with altitude

The total rainfall generally increases with increasing altitude and reaches a maximum somewhere between 1000 and 1500 m above sea level. The number of dry months decreases gradually with elevation until a certain height is reached above sea level, where it starts to increase again (Table 3.2). The point at which the number of dry months starts to increase again is also located between 1000 and 1500 m above sea level. This point coincides normally with the condensation level of water in the air, and at this level the ascending air cools, resulting in condensation of water vapor that produces a lot of rain, dense fog, and clouds. At the summit of the mountain, the number of dry months often equals zero (Table 3.2).

..

Variations in temperatures with altitude

Temperature decreases gradually with increasing altitude. With each 100-m increase in elevation above sea level, the temperature decreases by 0.6°C. The variation in temperature with increased elevation above sea level can be calculated with the aid of a formula developed by Braak (1925–1929): t = 26.3° – h × 0.6°C

(3.2)



Chapter three: Climate of Indonesia

Table 3.2 Altitudinal Variations of Rainfall and Climate in Indonesia

Location m

Rainfall

Climate

Mean Annual Rainfall

100 mm

Ka S&Fb

mm

Pasar Minggu

35

3.2

7.9

Afa

C

2173

Depok

95

2.0

9.9

Afa

A

3130

Bogor

266

0.3

11.5

Afa

A

4230

Tjiapus

540

0.1

11.8

Afa

A

4880

Pondok Gedeh

900

0.4

10.1

Af

A

3644

Mandalawangi

1800

0.6

10.6

Cfi

A

4201

Salak Volcano

2211

0.0

11.1

Cfi

A

5467

K = Köppen symbols; b S&F = Schmidt and Ferguson. Sources: Braak, C. (1931); Mohr, E.C.J. (1944); and Schmidt, F. H. and Ferguson, J.H.A. (1951). a

where 26.3° is the average temperature in Indonesia in degrees Celsius at sea level, and h is the elevation in hectometers.

..

Zonal divisions into lowland, upland, mountain, and high-mountain lands

The variations or changes in rainfall and temperature, with increased elevation above sea level, are the reasons for many attempts to divide the countryside into several altitudinal zones (Mohr, 1922; Schmidt and Ferguson,

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

Table 3.3 Zones of Lowland, Upland, Mountain, and High-Mountain Lands in Indonesia Mohr

Van Steenis

S&Fa

°C

Elevation m

Zone

Zone

Tropical Lowland

25–27

0–200

Tropical Zone

Lowland

Tropical Upland

14–19

200–1000

Tropical Zone

Upland

Tropical Mountain Land 13–18 1000–1800

Submontane

Upland

1800

Montane Zone

Mountain Land

2400–4100

Subalpine

Zone

Tropical High-Mountain 0–12 Land

S&F = Schmidt and Ferguson. Sources: Mohr, E.C.J. [1922, 1944]; Van Steenis, C.G.G.J. [1948, 1954]; Schmidt, F.H. and Ferguson, J.H.A. [1951]; and Junghuhn [1850].) a

1951; Van Steenis, 1948). On the basis of variations in temperatures with increased elevation, Mohr (1922, 1944) recognizes four zones from sea level to more than 1800 m above sea level (Table 3.3): 1. 2. 3. 4.

Tropical lowlands Tropical uplands Tropical mountain lands Tropical high-mountain lands

For comparison, zonal divisions are also provided, developed by Van Steenis (1948) and Schmidt and Ferguson (1951). As can be noticed in Table 3.3, they are much simpler than Mohr’s zonal concept.

Chapter three: Climate of Indonesia



The altitudinal limits for these zonal divisions of lands are believed to shift somewhat to higher or lower elevations above sea level in a tropical monsoon climate (Tan, 1958; Tan and Van Schuylenborgh, 1959; Van Schuylenborgh, 1958). The author also wonders whether it is not more appropriate using names such as tropical highlands and tropical mountain lands, respectively, for the tropical mountain lands (3) and high-mountain lands (4)? This is more in line and consistent with the usage of tropical lowlands and uplands. Mohr’s zonal concept above is based not only on the limits of temperature and location above sea level, but apparently also on suitability for the growth of certain crops and plants. For instance, the tropical lowland has been deined as the region not higher than 200 m above sea level and with temperatures not lower than 20°C. These conditions appear to be excellent for sugarcane and tobacco cultivation in Indonesia. However, in addition to the above factors, a monsoon climate is necessary for the ripening process and harvesting of the two crops. The tropical upland, originally called “Hilly Land,” is the zone between 200 and 1000 m above sea level. At ≥1000 m above sea level, coconut palm trees will not lourish. This is the zone of the tropical mountain land, where generally the condensation level of water vapor in the air is reached, increasing the relative humidity that consequently produces clouds and fog, often hovering constantly over the mountainsides. The conditions and composition of the vegetation cover then change visibly. The mountain trees are usually loaded with moss, and coniferous trees start to increase in numbers. One of the indigenous pine trees in Sumatra is the well-known



Soils in the Humid Tropics and Monsoon Region of Indonesia

Pinus merkusii, which has been used for transplanting on other islands for pulp production. Close to the summit, starting at ±2400 m above sea level, the timberline is reached. Van Steenis (1954) has called this the subalpine zone.

.

Signiicance of tropical and monsoon climates in pedogenesis

From the discussion above, it can perhaps be concluded that it is very dificult to designate the climate of Indonesia either as a monsoon climate alone or as only a tropical climate. Three main types of climates, at least, seem to occur in the archipelago. They are the tropical rain forest climate, the tropical monsoon climate, and the tropical savannah climate. The equatorial climate with its tropical rain forest is covered by the tropical rain forest climate. The name tropical humid climate is perhaps a better term than tropical rain forest climate, underscoring more the determining factor for climate, rather than the rain forest. A vegetation cover is the resulting expression of the prevailing climatic conditions. In general, the tropical humid climate prevails over most of the islands in the archipelago, and especially in Sumatra, Kalimantan, Sulawesi, Papua, and West Java. The tropical monsoon climate is restricted to Central and East Java and the western part of the Lesser Sunda Islands chain, whereas the tropical savannah climate is found to affect small regions only in the eastern part of the Lesser Sunda Islands, located under the inluence sphere of Australia. Because altitudinal variations in

Chapter three: Climate of Indonesia



the climate exist, the three main climatic forms will no doubt also be affected by these changes and will follow similar zonal divisions with increased elevation above sea level. These variations may have produced different “shades” in the prevailing main climate of the region, which are rather important from the standpoint of soil formation. The differences in climate will affect the type of vegetation, and this, in turn, will affect the nature of soils formed.

..

Balance effects between precipitation and evaporation in different climatic types

One of the effects of climate can perhaps be ascribed to the balance between precipitation and evaporation, which naturally will differ in different types of climates. The tropical monsoon climate will affect soil formation with alternating downward and upward movement of soil water in the pedon (soil proile). The upward movement due to the pull of evaporation, occurring mostly during the dry season, may vary in duration with the length of the dry season. It will be longer in the true monsoon climates and shorter where the dry season is weak and short. The soil will be leached during the wet season, but some of the elements lost, especially bases, will be retransported upward during the dry season. On the other hand, the tropical humid climate, characterized by a continuously wet condition, will affect soil formation with a rather constant downward movement of soil water. In this condition, the soil is constantly leached and tends to be more acid in reaction, due to the loss of bases, than the soil in the monsoon regions.



..

Soils in the Humid Tropics and Monsoon Region of Indonesia

Altitudinal variations in soil genesis and soil fertility

With increased location above sea level, soil organic matter content, and in particular humic acid content, tends to increase substantially. This factor, together with the cooler and wetter climate in the highlands or Mohr’s mountain lands, provides favorable conditions for mobilization of elements, especially Al, Fe, and Ca, in the form of chelates (De Coninck, 1980; Tan, 1986). Due to formation of metal–organic complexes, humic substances and other organic compounds may accelerate the decomposition of soil minerals, generally present in abundance in the young volcanic ash parent materials. The dissolution products have a very important bearing on soil genesis and fertility. Movement or mobilization of soil constituents is the main reason for horizon differentiation, a process yielding soils with different kinds of proiles. Current concepts in formation of spodic horizons are based on formation of aluminum- and iron-humic chelates. Their mobilization to the B horizons causes the formation of the spodic horizon, a main characteristic of spodosols or podzols. This process was called in the past “podzolization,” a name that was phased out by the U.S. soil survey division, creating confusion and arguments from a lot of international scientists. Podzolization generally occurs in cool and humid conditions in temperate regions under coniferous or other types of vegetation yielding acid humus. An almost similar condition can be found in Indonesia only in the highlands or the tropical mountain-lands zone. Several

Chapter three: Climate of Indonesia



other aspects in soil genesis related to organo-complex formation will be discussed in Chapter 5, including formation of albic horizons and translocation of clays. In addition to its role in soil genesis, organo-metal chelates play an important role in micronutrient availability to growing plants and hence beneit soil fertility in general. Because of chelation, Lindsay (1974) reported that mobilization by diffusion and mass low of micronutrient elements to plant roots was made possible. The chelates are believed to provide the carrier mechanism by which depleted micronutrients at the roots can be replenished. However, availability of chelated iron, zinc, and manganese is reported to be dependent on pH and stability of the organo-metal complexes. The cooler climate of the tropical highlands is also ideal for the cultivation of many temperate region crops, such as Irish potato, carrots, caulilower, and cabbage. The fresh produce can be harvested year long for sale at local markets or in shops of big towns, such as Jakarta, Bandung, Surabaya, and Medan. The latter proves to be a very lucrative business for local farmers. Conditions in the lowlands are quite different from those discussed above for the mountain-land zone. Due to the higher temperatures, decomposition of soil organic matter in the lowlands generally occurs at a very rapid rate, and hence, soil organic matter contents are substantially lower than in the mountain lands. The main soil formation process in the lowlands is considered desiliciication, by which silica is released from soil silicates by the prevailing drastic weathering due to high temperature and humid conditions. Part of the silica reacts with aluminum to form clay, and another



Soils in the Humid Tropics and Monsoon Region of Indonesia

part is subject to leaching in the constantly humid conditions. Mobilization of iron and aluminum is at a very minimum in the absence of adequate amounts of humic acids, and these elements, instead, tend to accumulate in the soil. The processes, as described, may also occur in temperate regions but are usually more pronounced in the humid tropics (Tan, 1998). In the past, such a process of soil formation was known as laterization or ferralitization. In essence, it is the reverse process of podzolization. The soils formed were called latosols, the oxisols in today’s U.S. Soil Taxonomy. In the uplands, the zone between the lowlands and the highlands or mountain lands, both podzolization and laterization processes can occur simultaneously.

chapter four

Vegetation of Indonesia .

Climax vegetation

The vegetation is believed to relect the climatic pattern of a particular region or country. The climate is expected, in general, to put its imprint on the vegetation developing in the region. Consequently, the growth of the vegetation is adapted to and in balance with the prevailing climatic conditions. The type and composition of this vegetation, dictated by the climate, are called by Jenny (1941) the climax association. Therefore, different types of vegetation are present in Indonesia due to the presence of different types of climates. Because three major types of climates are recognized in Chapter 3, three different types of climax vegetation may be present in Indonesia—the tropical rain forest, the tropical monsoon forest, and the tropical savannah forest.

..

The tropical rain forest

The tropical rain forest exists in the constantly wet areas of the humid tropics. It is generally characterized by 



Soils in the Humid Tropics and Monsoon Region of Indonesia

evergreen forms of vegetation, as far as it has not been destroyed for farming and timber production. In its original state, the forest looks awesome and impenetrable due to an abundance of very dense vegetative growth. In general, it is composed of a wide variety of plant species, and only in very few exceptions can one ind a rain forest stand composed of a single plant species. Another characteristic of the tropical rain forest is that it often forms three distinctive layers of canopies. The highest canopy is formed by very tall trees, often 40 to 60 m high, towering into the sky as rather isolated or widely spaced trees above the second layer of the rain forest. This second level is formed by 20- to 30-mtall trees that are grown more closely together, hence yielding a dense canopy, like a roof. Below this second level, a third level exists, consisting of small young trees growing between a population of a variety of shrubs and other types of ground vegetation. A large number of creeping palms, thorny rattan plants, and many types of lianas, climbing upwards from one tree trunk toward another, add to the tangled image of a thick and dense undergrowth. A layer of fresh litter, consisting of dead and half-decomposed leaves and twigs, covers the soil. In general, it takes at least 50 years to form a 20-cmthick litter layer under a healthy rain forest. This litter layer is the lifeline for the rain forest due to its role in nutrient cycling (Tan, 2000).

..

The tropical monsoon forest

The tropical monsoon forest exists in the tropical monsoon climate. The southeastern part of Indonesia in

Chapter four: Vegetation of Indonesia



particular is covered by typical monsoon vegetation. In general, it is mixed with a number of deciduous trees that shed their leaves in the dry season. Though most of the trees are not that tall, some can be as tall as those of the tropical rain forest. For example, teak (Tectona grandis), a characteristic monsoon forest tree, can grow as tall as 50 m. The trees in a monsoon forest also grow rather widely spaced from each other.

..

The tropical Savannah forest

The tropical savannah forest occurs only in limited areas, such as in the eastern part of Nusa Tenggara, which is under the inluence sphere of the arid and desert regions of Australia. It hardly resembles a true forest, because the vegetation is substantially thinner or less dense than that of the tropical monsoon forest. The trees of the savannah forest (for example, Acacia and Eucalyptus species) are more adapted to long dry seasons. With lots of grass vegetation between the widely spaced trees, the tropical savannah forest, looking more like a park landscape, is excellent for grazing. The remaining wildlife is unique to this region, especially the small wild horses. Unfortunately, these horses are now on the endangered species list, if not already considered extinct.

.

Vegetation provinces

Another method of describing the vegetation of Indonesia is the concept of Van Steenis (1948), who divided the archipelago into three vegetation provinces, each

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

characterized by a distinctive association of forest vegetation, composed of speciic plant genera. Van Steenis’ three vegetation provinces are the West Indonesian, East Indonesian, and South Indonesian vegetation provinces.

..

West Indonesian vegetation province

This province, characterized by a Dipterocarpaceae rain forest (Figure 4.1), is subdivided as follows: 1. Dipterocarpaceae and Pinus forest of North Sumatra. 2. Dipterocarpaceae and Ironwood (Eusideroxylon zwageri) forest of South Sumatra. 3. Dipterocarpaceae forest of Kalimantan, with Ironwood on the southeast coast.

..

East Indonesian vegetation province

This province, characterized by an Agathis rain forest, is subdivided as follows: 1. Agathis forest of Sulawesi. 2. Agathis forest with Ironwood, Melaleuca, and sagopalm (Metroxylon spp.) of Maluku. 3. Agathis forest and alpine grassland in the Snow Mountain range of Papua (West Irian).

Chapter four: Vegetation of Indonesia



Figure 4.1 The Diterocarpaceae rain forest in the lowland of North Sumatra with its dense undergrowth.

..

South Indonesian vegetation province

This province is characterized by a monsoon forest and is divided as follows:



Soils in the Humid Tropics and Monsoon Region of Indonesia

1. Teak (Tectona grandis) and Casuarina forest of Central and East Java. 2. Casuarina forest of Bali and Lombok. 3. Savannah vegetation on the eastern islands of Nusa Tenggara and, in particular, in Timor. These islands are also famous for sandalwood (Exocarpus latifolia and Santalum album). In addition to the major plant species listed above, the three provinces are home to numerous other plant genera. On the slopes of Mount Lawu in Central Java (South Indonesian Vegetation Province), there are extensive forest areas with trees, identiied by Bloembergen, Professor of Botany at Institut Pertanian Bogor (IPB; Indonesia), as Querqus spp. (personal communications). For more detailed information on the vegetation of Indonesia, the readers are referred to the multivolume Flora Malesiana by Van Steenis (1954). Perhaps also of importance is the work of Heyne (1950) and the detailed vegetation map of the Forest Service of Indonesia as compiled by Hannibal (Figure 4.2). It should be realized that this vegetation map of Indonesia dates from the early 1940s to 1950s, and the vegetation cover of Indonesia has since then been changed drastically by wide-scale deforestation for crop and timber production, including illegal logging, and by the resulting disastrous wildires. Efforts have been made to assess the destruction and the extent of the remaining vegetative cover. By applying modern techniques, such as Landsat satellite imagery, the Forest Service of Indonesia is trying to update old data and old maps.

Figure 4.2 Vegetation Map of Indonesia by Hannibal (1940–1950). (Courtesy of Badan Planology Kehutanan Indonesia. Forest Service of Indonesia, Jakarta.)

Chapter four: Vegetation of Indonesia





Soils in the Humid Tropics and Monsoon Region of Indonesia

.

Altitudinal vegetation zones

Because the vegetation will follow a speciic climatic pattern, as indicated in the aforementioned pages, in view of the presence of altitudinal changes in the climate of Indonesia, several vegetational zones can also be distinguished with increased elevations above sea level. In general, ive main types of climax vegetation are recognized from the lowlands to the high-mountain lands— the coastal lora, the rain forest, the mountain forest, the cloud-belt forest, and the subalpine/alpine vegetation. These altitudinal vegetation zones may occur both in the humid tropics as well as in the tropical monsoon regions. Some people may perhaps object, considering the coastal lora as a zone of vegetation, caused by altitudinal changes in climate. It is added here for the sake of completeness, because the discussion starts from sea level.

..

The coastal lora

The coastal form is a determining factor in the formation of a coastal lora. Where extensive low-lying areas are present, strongly inluenced by the tides of the sea, a Mangrove forest develops with many Rhizophora plants, locally called bakau or bako-bako plants. Another wellknown mangrove plant is the Nipah palm (Nipa fructicans), whose leaves are used by local folks to make baskets and roof-thatch. This kind of forest usually lourishes on river mud under saline conditions. At the more sheltered beaches, the gently shelving shorelines of the Sunda shelf are usually bordered by such a mangrove belt, varying in width from a few 100 m to several

Chapter four: Vegetation of Indonesia



km. These are the kinds of swamps, often foul smelling, that occur extensively on the east coast of Sumatra, southern and southwestern coasts of Kalimantan, and the southern coastal plain of Papua. The seawater brings with the tide large amounts of sulfates that are retained by the coastal sediments. Under anaerobic conditions, the sulfates are reduced into H2S, which in turn will react with iron to form FeS, giving to the sediments a dirty black color (Tan, 2000). Together with the offensive stench caused by the H2S gas, the dirty polluted appearance often turns people away. Nevertheless, the mangrove forest area provides shelter for many forms of wildlife and is an important breeding ground for many types of ish, shrimp, and shellish. It is typical to ind that more inland, the mangrove vegetation changes gradually into a brackish then into a freshwater swamp vegetation. As soon as the soil becomes mixed with more sandy material and the saline condition decreases inland-ward, the typical mangrove plants disappear gradually and rather selectively. First to disappear are the Rhizophora plants of the Avicennia spp. (locally known as kayu api), then second in line are the Nipah palms. The freshwater swamp forest behind the mangrove belt supports a large variety of other palm trees. The Pinang palm (Areca catechu) trees lourish in this kind of swamp and are sometimes found as “monocultures” (Figure 4.3). The nuts, known as betelnuts, are favored as food by some wild cacatuas and are used for chewing-consumption by local folks. They are believed to be addictive, similar to chewing tobacco, and bad for human health because of their contents of carcinogens. Another characteristic tree of the freshwater



Soils in the Humid Tropics and Monsoon Region of Indonesia

Figure 4.3 A “Pinang palm” (Areca catechu) forest in Ceram (Moluccas) developed at riverbanks and loodplains under an Afa (Köppen’s) climate type. The author is shown (on the left) with his soil survey crew.

swamp area is the sago palm (Metroxylon spp.) that is often harvested by the people (Figure 4.4). The starch from the pith of the tree is used as food, in the thickening of gravy, or as glue and for the stiffening of clothes. Quite a different type of coastal vegetation will develop if the coast consists of a broad sandy beach. In this case, dune formation often occurs, as is found along the

Chapter four: Vegetation of Indonesia



Figure 4.4 A typical “sago palm” (Metroxylon sp.) forest in the Moluccas, developed in river loodplains and freshwater swamps.

northeast coast of Madura and the coastal regions bordering the Indian Ocean on the south and southwest coasts of Java. More inland, behind the dunes, a beach forest usually develops, consisting of trees with fall-tinted leaves and beautiful lowers, such as the Ketapang tree (Terminalia catappa), the Hibiscus plants, and the Erythrina trees.



Soils in the Humid Tropics and Monsoon Region of Indonesia

The edible nuts of the Ketapang tree are often collected for local consumption. However, on the sandy beaches, exposed to the sea, a variety of salt-tolerant grasses grow (for example, Spinifex littoreus, locally known as rumput angin [grass that breaks the wind]). This grass vegetation is apparently protecting the beaches by encouraging the dunes to form. Large numbers of coconut palms also grow on the exposed beaches. Where the palm trees are absent, Casuarina equisetifolia trees can be found growing on the shorelines. The latter trees are locally called camara (Indonesian for pine) trees, due to their long needle-like leaves similar to pine needles.

..

The rain forest and the mountain rain forest

Moving inland, the coastal vegetation gives way to a rain forest as soon as the conditions become favorable for its development. The rain forest starts at sea level but can extend toward higher elevation. Usually the plants or trees of the rain forest are very large and tall, often taller as compared to those of the temperate regions. Temperate region trees that can reach a height of 50 m belong to the Quercus sp. In the humid tropics, a number of jungle giants more than 60 m high are present. They are usually adorned with the typical “plank roots.” Another characteristic of a tropical rain forest is the proliic growth of lianas, rattans, and an assortment of other epiphytes. As this rain forest extends to higher elevations, its composition changes with increasing altitude. Perhaps, at elevations of 100 m above sea level, some typical plants begin to disappear. Lianas and rattans become

Chapter four: Vegetation of Indonesia



gradually more slender and grow very poorly. Other plants will start to disappear or decrease in numbers at 500 to 700 m above sea level, whereas temperate region plants then make their appearance between the indigenous lora. This is, for instance, the case with the Dipterocarpaceae that decrease in number at this high elevation. At the same time, plants, typical for a mountain lora, appear and gradually increase in number. For example, at an elevation of 500 m above sea level, Quercus (oak or Kayu pasang) and Castanea javanica (locally called Ki hiyur) or Castanea argentea (Saninten) trees start to lourish. The fruit of the Saninten tree resembles the temperate region chestnut. At higher elevation, the Schima noronhae tree (Kayu puspa) becomes dominant. The latter is considered a truly typical mountain tree. In many regions, the mountain lora may be dominated by a single species of trees. Such is the case with the coniferous forest in North Sumatra and in Central and East Java. In these regions, the mountain lora tends to be dominated by Pinus merkusii, an indigenous pine species, as indicated before. The inluence of a monsoon climate on the rain forest and mountain lora can be noticed by the appearance of plants adapted to a periodic drought period. Then the lora consists more of deciduous plants, such as Tectona grandis (teak) in the lowlands, and Quercus trees in the case of a mountain forest.

..

The cloud-belt forest

This name is probably better than the name “High Mountain Forest” as given by Mohr (1922). With

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

increasing altitudes, the mountain rain forest, as discussed in the preceding section, is gradually replaced by a cloud-belt forest. The conversion starts to take place when the condensation level of water vapor in the sky is reached. At this elevation, lots of fog, mist, and clouds are consequently produced, which usually hang over the mountainsides. This is why the name cloud belt is preferred in this book. This condensation level may be reached at 1000 to 1500 m above sea level, but depending upon the conditions elsewhere, it may also begin at an altitude of 2000 to 2400 m. The cloud-belt forest is sometimes considered an impoverished type of a mountain rain forest. Due to the misty conditions producing high relative humidity, its lora is typiied by trees draped by many kinds of mosses. At the lower boundary of the cloud-belt zone, plants typical of the mountain rain forest still exist, though in decreased numbers. With increasing altitudes, they soon disappear to be replaced by increasing numbers of Laurantaceae, Myrtaceae, and coniferous plants. At the highest boundary of the cloud-belt forest, the trees are often distorted in appearance and stunted in growth. These trees, knotty and gnarled by the cold mountain winds, will soon also disappear when at higher elevation the timberline is reached.

..

The subalpine vegetation

At higher elevations above sea level, the cloud-belt forest will be replaced by a subalpine vegetation. As indicated above, at the highest boundaries of the cloud-belt zone, the trees can still be relatively tall, though they are more

Chapter four: Vegetation of Indonesia



dwarfed and gnarled in appearance, especially when the “tree level” or “timberline” is reached. This level depends on the local climate, topography, and geomorphology, but generally it starts at approximately 2400 to 3000 m altitude above sea level. The large luctuations between maximum and minimum temperatures at these highest elevations in Indonesia, together with the low relative humidity and low air pressure, require exceptional adaptation for the vegetation to grow. This cold and windy area above the timberline is often called the subalpine zone. However, true alpine conditions exist only in the Snow Mountain range of Papua (West Irian). Due to low temperatures and ierce winds, the vegetation tends to be grasses, bunch grasses, and shrubs. Most of the shrubs have felt or velvety and hairy leaves and twigs as adaptations and protection against the severe or harsh growing conditions. A good example of such a plant is the Edelweiss plant (Anaphalis javanica or Leontopodium alpinum) found on the mountaintops in Java and South Sulawesi. At the lower boundaries of the subalpine zone, close to the timberline, some dwarfed and distorted trees can still be seen growing in the bleak landscape. Some rhododendron shrubs are also found struggling to survive at this altitude. Sporadic surveys and visits to the top of the mountains in Java, with their subalpine vegetation and areas of pollengrass or bunch grass, gave the impression to the author of this book that they somewhat resemble the Tussock grassland in the mountains of New Zealand.

chapter ive

Soil formation, classiication, and land use .

Soil-formation factors

By previous conventional standards of pedology, the character of the soil is attributed largely to the effect of interactions of ive major factors of soil formation: climate, vegetation, parent material, topography, and time (Jenny, 1941; Joffe, 1949; Robinson, 1951; Taylor and Pohlen, 1962). Apparently this concept is still relevant today, because it has not been challenged, but, instead, has been quoted in many modern textbooks of soil science (Brady and Weil, 1996; Miller and Gardiner, 1998; Soil Survey Staff, 2006b). As explained in the preceding chapters, many kinds of rocks and volcanic parent materials, several types of climates, different forms of vegetation, a great variation in topography, and landforms of different ages are present in Indonesia. Though a great variety of soils may have been expected to form in view of so many differences in soil-forming factors, surprisingly this 



Soils in the Humid Tropics and Monsoon Region of Indonesia

seems not to be the case. The pattern of the soil’s distribution in the archipelago is also more regular as would not have been expected from the presence of the large number of different soil-formation factors.

.

Soil-forming processes

The interaction of the factors of soil formation may be expressed by a series of soil-forming processes, which generally involve complex physical, chemical, and biological reactions. The reactions may occur simultaneously, or a sequence of reactions one after another is involved. Generally, it is believed that the soil is formed by the combined action of additions of organic matter and inorganic materials to the surface, transformation and new formation of compounds within the pedon, vertical transfer of soil constituents, and removal of soil components from the soil body (Simonson, 1959; Taylor and Pohlen, 1962). The type of processes involved varies according to the conditions, and many processes have been recognized in this respect as reasons for the formation of different kinds of soils in the world (Buol et al., 1973; Robinson, 1951; Taylor and Pohlen, 1962). Previous well-known processes of soil formation are, for example, laterization, podzolization, calciication, salinization, and gleyzation, representing processes for warm humid, cool humid, semihumid, arid, and poorly drained conditions, respectively. Unfortunately, this concept of soil-forming processes has been phased out by the U.S. Department of Agriculture (USDA) Soil Survey, which is promoting a concept based solely on soil morphology (Soil Survey Staff,

Chapter ive: Soil Formation, Classiication, and Land Use



1975, 2006a). Differences in soils are determined by soil proiles only, which are deined as the major factor for causing variations from soil to soil. A number of diagnostic properties have been developed and assigned to several of the soil horizons for use in identiication of soil differences (Soil Survey Staff, 1975, 2006a, 2006b). The soil-forming process in question should then be read between the lines. This idea of the USDA is apparently considered an excellent concept, because many agreed to use it without question. However, a large number of scientists also have voiced concerns that the U.S. Soil Taxonomy system is often not applicable to conditions different than those in the United States. Many also believe that the concept is too artiicial and somewhat distorted to it U.S. conditions. It should be revised and adapted appropriately when used in quite different or foreign soil ecosystems. Reading soil-forming processes in abstraction from morphological data is very risky and may lead to different interpretations. The following issues may serve as an example about the dificulties using the USDA system. Questions have arisen, for instance, as to what the soil-forming process of oxisols is in the USDA system. Considering oxisols to be formed by oxidation is very unclear for many, whereas relating the concept of ECEC (effective cationexchange capacity), one of the diagnostic properties for an oxic horizon, to an oxidation process is stretching too far the principles of oxidation in soil chemistry. In addition, the identiication of oxisols solely on their morphological characteristics is often very confusing in Indonesia and many other countries, because several of the morphological features are to the eye often similar



Soils in the Humid Tropics and Monsoon Region of Indonesia

to those of ultisols and some alisols in the lowlands. Many more examples can be given, but it is beyond the scope of this book to address the weaknesses and strengths of the American system. It is suficient to say here that the USDA Soil Taxonomy is an excellent system, but abandoning or phasing out well-established concepts of soil-forming processes is perhaps unwarranted, if not arrogant. Why can the theories of soil-formation processes not exist side by side with the USDA Soil Taxonomy system? As far as can be noticed, the two theories do not conlict with each other and can be used to support each other. Scientists around the world have frequently, but discretely, used the processes of soil formation to underscore or emphasize the presence of a soil after doubts were raised when applying the U.S. Soil Taxonomy (FAO-UNESCO, 1998, 2006, 2007a). Many of the allegedly old terms, for example, podzols and saline soils, are still in use in Germany and the United States, respectively. The advantage of using both systems in parallel can be summarized by the following conclusion. By recognizing the factors of soil formation, the soil-formation process, and relected characteristics in the soil proile, geographic units of soils may be distinguished more properly and their distribution mapped. For completeness, the soil-formation processes will be discussed in the following sections, and their interpretation in somewhat more modernized versions addressed.

..

Previous concept of soil-forming processes

In the early stages of development of the concept, only ive major soil-formation processes are considered of

Chapter ive: Soil Formation, Classiication, and Land Use



importance, as indicated above in the preceding section. However, several other processes have been discovered and added since the 1950s. The additions include ferralization and allitization (Kovda, 1964; Robinson, 1951), lixiviation (Mohr, 1922; Mohr at al., 1972), rubiication (Kubiena, 1962), illimerization (Kanno, 1961), argillization, and melanization (Taylor and Pohlen, 1962). For the purpose of explaining the meaning of the terms, a list of the soil-forming processes is given below: 1. Laterization: This is a process in which silica and bases tend to be lost with the subsequent accumulation of sesquioxides in the pedon. A warm humid climate is a requirement for a complete decomposition of primary minerals, releasing the Si, bases, Al, Fe, and other components. The soils produced were called latosols, lateritic soils, and laterites. Using the U.S. Soil Taxonomy, these soils are renamed today as oxisols. The additional processes, as proposed earlier by Robinson (1951) and Kovda (1964), are, in this author’s opinion, only subprocesses of laterization. Therefore, the present author suggests dividing laterization into the following two subdivisions: a. Ferralization: A subprocess of laterization involving also strong chemical weathering, by which silica is removed, causing sesquioxides, mainly Fe2O3, to accumulate. b. Allitization: This is the second subprocess, also involving strong chemical weathering by which silica is removed and leaving Al2O3 to accumulate in the residue (= soil).



Soils in the Humid Tropics and Monsoon Region of Indonesia

The two subprocesses are often used by Food and Agriculture Organization (FAO [United Nations]) scientists, which in combination are believed by the present author to be the reason for the development of the FAO ferralsols. The latter can be considered another alternative name for latosols or oxisols. 2. Podzolization: This term is still used today by the FAO and WRB (World Reference Base for Soil Resources) systems for the formation process of podzols by which a rapid translocation takes place of iron, alumina, clay materials, and humic acids to the B horizons, yielding soil proiles with well-developed eluvial E and illuvial B horizons. Bases are also depleted by leaching, causing the soils formed to become very acidic. In a sense, the process is a reverse process of laterization. It requires the presence of a cool humid climate and vegetation yielding acidic humus. The humic acids formed play an active role in the mobilization process by forming aluminum and iron chelates. The processes of mobilization of aluminum, iron, and clays in the form of metal (clay)-organo chelates are called cheluviation (leaching) and chilluviation (accumulation) by the FAO and WRB systems (FAO-UNESCO, 2007c). The soils produced were called podzols, brown podzolic, and gray-brown podzolic soils, which translate into spodosols and alisols, respectively, in the new U.S. Soil Taxonomy. The name podzol is still used in Germany and many other East European countries, as indicated above.

Chapter ive: Soil Formation, Classiication, and Land Use



3. Calciication: This term is used for a process of soil formation in which the surface soil is kept supplied with calcium to saturate the soil colloids to a high degree, rendering them in this way relatively immobile. This process requires the presence of a semihumid to semiarid climate, as found in the Midwest of the United States, in the Mediterranean, and in the monsoon regions of Indonesia. The process yields soils previously called chernozems, brown forest soils, and red-yellow Mediterranean soils. The equivalents in the U.S. Soil Taxonomy are the mollisols, inceptisols, and alisols, respectively. 4. Salinization: This is the name for a soil process by which soluble salts tend to accumulate in the soils. The process requires an arid climate where the average precipitation is less than 500 mm (20 in.) annually. The amount of H2O from precipitation is insuficient to neutralize the amount lost by evaporation and evapotranspiration. As the water is evaporated in the atmosphere, the salts are left behind to accumulate. In the past, the soils developed were called saline soils, solonchaks, or white alkali soils. Today these soils are called aridisols by the U.S. Soil Taxonomy. a. Solonization: This is a process of removal of excess salts from the solonchaks, producing solonetzic soils or solonetzs, which are called aridisols by the U.S. Soil Taxonomy. b. Solodization: This is a process of translocation of salts and highly dispersed soil colloids to deeper horizons. The salts accumulated by

00

Soils in the Humid Tropics and Monsoon Region of Indonesia

salinization may eventually saturate the soilexchange complex with Na. Increasing the sodium saturation is in fact a sodication process that also results in increasing the soil pH. The latter is referred to as alkalinization; hence, solodization is often also called sodication and alkalinization. The soils produced were previously called solods, sodic soils, or black alkali soils. Today they are the aridisols of the U.S. Soil Taxonomy, no difference in name or nomenclature from the saline soils. Note: The “older” names given above for the saltaffected soils are still in use today. However, the groups have been simpliied, and each is distinguished by criteria on the basis of electrical conductivity (EC), and exchangeable sodium percentage (ESP) (Miller and Gardiner, 1998; Richards, 1954; Tan, 1998): 1. Saline soils are characterized by values of EC 4 mmho/cm at 25°C and ESP < 15%. The dispersion of saline soils starts at ESP = 15%. The soil pH is ordinarily ≤ 8.5. 2. Saline-alkali soils are soils with EC > 4 mmho/ cm at 25°C and ESP > 15%. The soil pH is normally ≥ 8.5. 3. Nonsaline-alkali soils have EC < 4 mmho/cm at 25°C and ESP > 15%. The soil pH ranges from 8.5 to 10. The selected criterion of 4 mmho/cm is supposed to be the limit at which salt damage to

Chapter ive: Soil Formation, Classiication, and Land Use

5.

6.

7. 8.

9.

0

crops starts to occur (Kamphorst and Bolt, 1976; Richards, 1954). Gleyzation: This is a soil-forming process under the inluence of excessive moisture conditions, normally caused by poor drainage. Sometimes also referred to as gleying (Taylor and Pohlen, 1962), the process takes place in anaerobic environments, where iron is reduced yielding the speciic grayish and rusty colors. It often occurs in the presence of organic matter in wet soils with low or deicient oxygen content. The process is not restricted to any type of climate and can occur intrazonally. The soils formed are called in general terms, hydromorphic soils, though gleysols are recognized in the FAO and Canadian systems of Soil Taxonomy. The U.S. Soil Taxonomy placed them in an aqua suborder. Lixiviation: This is a process involving mechanical removal of ine materials from the upper soil layers, without the breakdown of primary minerals and without the activity of soil organic matter. Rubiication: This is a nonlateritic red earth formation, used by Kubiena (1962) in soil micromorphology, characterizing a soil fabric he called rotlehm. Illimerization: This is a process of clay migration to deeper layers in the soil proile and is also known under the names of lessivage and perhaps ferralitization. It is not exactly a soil-forming process, but more the reason for formation of Bt or argillic horizons of the U.S. Soil Taxonomy. Argillization: This is the formation of clays by chemical decomposition or weathering of minerals in the parent rocks.

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

10. Melanization: This is the formation of thick dark surface horizons, enriched with soil organic matter with narrow C/N ratios. The U.S. Soil Taxonomy recognizes a melanic epipedon. The irst ive in the list above are the major soil-formation processes that were well established and extensively used before they were phased out in the United States. The remainder (6 through 10) are not exactly soilforming processes, but only big noises from well-known scientists. The latter is perhaps one reason why the USDA Soil Survey Division is opposed to using them. As can be noticed from the descriptions, they are more responsible for formation of a speciic soil horizon, or are just simply weathering processes without forming a speciic soil.

..

Today’s versions of soil-forming processes

Efforts have also been made by several scientists to replace the traditional soil-forming processes as discussed above with new terms, which boils down to modernizing the old versions only. The new versions of soil-forming processes with applicability to the development of pedons, such as desiliciication, will be discussed below, including translocation of clays and of aluminum and iron, which are more related to the formation of argillic, albic, spodic, and oxic horizons.

...

Desiliciication

Desiliciication is a process in which silica is released from soil silicates. Part of the silica reacts with alumina

Chapter ive: Soil Formation, Classiication, and Land Use

0

to form clay, whereas the remainder is subject to leaching. Consequently, the soil will lose its silica but at the same time will gain sesquioxides and other types of clays due to residual accumulation of stable weathering products. This process may occur in the tropics or in temperate regions in the presence of suficient amounts of moisture and the right temperature. Usually it is more pronounced in the humid tropics. As can be noticed from the explanation above, it is just a new name for a previously well-known soil-forming process called laterization or ferralitization. A continued disiliciication process over geologic time periods will ultimately transform the Al2O3 minerals into bauxite (Tan, 1998). The solubility of silica is dictated by the law of polymerization. Silica remains soluble at concentrations of 140 mg/L in the pH range of 2 to 9 (Krauskopf, 1956; Millot, 1970; Tan, 1998). Polymerization occurs when the concentrations of silica exceed 140 mg/L, but this can be prevented by the presence of humic acids. Humic substances and other organic acids are known to form complexes or chelates with silica, as illustrated in Figure 5.1. In the form of a chelate, silica remains soluble and is free to move with the percolating waters, a process enhancing desiliciication. The author believes that this is the process by which silica and organic matter are lost during the formation of oxisols. It explains the low silica-to-sesquioxide ratios and low organic matter contents in oxisols.

...

Siliciication

This is a reverse process of desiliciication that occurs under poorly drained conditions and low permeability.

0

Soils in the Humid Tropics and Monsoon Region of Indonesia OH OH

Si

O COOH

OH Complex Formation

O

OH Si

COO

OH Chelation

Figure 5.1 Complex formation and chelation between monosilicic acid and humic acid. (From Tan, K.H. [1998].)

Leaching is inhibited, preventing loss of silica. The resulting increase in H4SiO4 activity may lead to the formation of smectites and illites, characterizing the vertisols in the lowlands of East Java (Tan, 1998; Van Schuylenborgh, 1971). Under changing physicochemical conditions, smectite can be transformed into kaolinite and the latter into gibbsite, or vice versa, by desiliciication and siliciication processes, as illustrated in Figure 5.2. These reactions are referred to as transformation by Singer (1979).

...

Translocation of clays

This process, leading to the enrichment of B horizons with clays, was earlier called illimerization or lessivage (Buol et al., 1973; Taylor and Pohlen, 1962). Such B horizons are referred to as argillic (Bt) horizons in

Chapter ive: Soil Formation, Classiication, and Land Use

0

Desilicification O2 or OH Al Si

Smectite

Kaolinite

Gibbsite

Silicification Figure 5.2 Desiliciication and siliciication of smectite, kaolinite, and gibbsite. (From Tan, K.H. [1998].)

the U.S. Soil Taxonomy. Why did the USDA Soil Survey suggest terminating this concept of soil-forming processes, favoring the use of soil morphology? In the author’s opinion, the terms illimerization or lessivage are more attractive and more explanatory than the use of morphology or proile characteristics. The same is true for laterization, podzolization, and the like. The migration of clays from A to B horizons is made possible by peptization of the clays, which is enhanced by interactions of the clays with humic acids (Greenland, 1971; Tan, 1976). Though the exact mechanism is not known, the hypothetical reaction, as shown in Figure 5.3, serves as an example. The reaction adds an acidic group (COOH) to the clay surface and increases the negative charge of the clay. The surface potential of the clay–organic complex is then larger than that of the clay alone. Consequently, the electrokinetic potential, related to the zeta (ζ) potential, becomes larger. As a

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

Si

O Al

Si

OH + HO

COOH

O

CLAY

Org. Comp

Si

O Al

Si

O

COOH + H2O

O

Clay-Organic Complex

Figure 5.3 Formation of humo–clay complexes.

clay–organic complex, the clay remains suspended for a longer time and moves downward with the percolating water. Several reactions are responsible for deposition and clay accumulation in the B horizon. Movement of clay stops where the percolating water stops, resulting in locculation of clay. Capillary withdrawal of water from the pores into the soil fabric deposits clay on walls of pores and peds, producing the argillans or clay skins.

...

Translocation of aluminum and iron

The downward movement of aluminum and iron together with organic matter results in formation of albic (E) and spodic (Bhs) horizons. This process was called podzolization, giving rise to formation of podzols (spodosols). Several scientists believe that podzols

Chapter ive: Soil Formation, Classiication, and Land Use

0

are formed by a process called lessivage. However, the latter process may explain the formation of argillic (Bt) horizons but does not justify the translocation of aluminum, iron, and organic matter, required for the development of spodic horizons or podzols. Most of the iron subject to translocation comes from the decomposition of biotite and ferromagnesian minerals. For mobilization of iron to take place, the soils must be well drained, and hence, most of the iron is in oxidized form—in other words, it is in Fe(III) ionic form. The possible ionic forms of Fe(III) are Fe3+, Fe(OH)2+, Fe(OH)2+, Fe2(OH)4+, and Fe(OH)4− (Van Schuylenborgh, 1966). For more details on the chemistry, solubility, and mobilization of Fe compounds, including redox reactions, reference is made to Tan (1998). Almost all soil silicates are sources for aluminum. The ionic forms of Al(III) are Al3+, Al(OH)2+, Al(OH)2+, Al(OH)4−, Al2(OH)24+, Al2(OH)42+, Al4(OH)102+, and Al6(OH)126+. For more details on the chemistry, solubility, stability, and mobilization of Al, reference is made to Tan (1998) and Van Schuylenborgh (1966). The general consensus is that the pH range in many soils is such that most of the aluminum and iron compounds are essentially insoluble and hence immobile. The possibility of migration of aluminum and iron in their ionic forms shown is very small. Other agents are required to make them more soluble. Evidence has been presented that decomposition products of soil organic matter, and especially humic acids, are capable of solubilizing the insoluble substances by complex reactions or chelation (Tan, 2003). As a complex or chelate, aluminum and iron may remain soluble at pH ranges that

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

make them usually insoluble. Stability and mobility of these complexes depend also on the metal concentration in the soil solution and saturation of the humic exchange sites. If the aluminum or iron concentrations are low, complexes will be formed in the A horizon with low metal/organic ligand ratios. In this case, the amount of silicon and iron chelated are insuficient to cause immobilization of the organo-metal compounds. The complex or chelate is then free to move down the pedon (De Coninck, 1980). During the downward migration, the chelates may pick up additional polyvalent cations, resulting in progressively decreasing their negative charges. The presence of higher cation concentrations in the subsoil and an acidity different from that in the A horizon may eventually neutralize the remaining charges. The consequent precipitation of the chelates gives rise to the development of spodic (Bhs) horizons, diagnostic for spodosols (podzols) of the U.S. Soil Taxonomy.

...

Redox reactions

Reduction and oxidation reactions occur in almost any soils but have not been regarded or emphasized as a soil-forming process. Redox reactions, in fact, contribute to formation of plinthite and gley horizons (Tan, 1998). Gleying is especially signiicant in poorly drained soils, such as the paddy soils where artiicial inundation of the soil is a required operation for the cultivation of lowland rice (Tan, 1968). By deinition, reduction is a gain in electrons, whereas oxidation is a loss of electrons, as illustrated by the classical reaction as follows:

Chapter ive: Soil Formation, Classiication, and Land Use reduction   → Fe2+ Fe3+ + e− ←  oxidation

0 (5.1)

Oxidation reactions usually occur in well-drained soils. On the other hand, reduction processes are more likely to be predominant in poorly drained soils or where excess water is present. Usually known as the soil redox state, this condition occurs in almost any soils. Both oxidation and reduction conditions can occur simultaneously in the soil. While the surface layers of the pedon are in an oxidized state, the subsoil layers may be in a reduced condition owing to a luctuating groundwater level. The latter may lead to pseudo-gley formation or to plinthization. The redox system in soils affects stability of iron and manganese compounds. To a certain extent, microbial activity and accumulation of organic matter are also affected. Fresh organic matter is thought to aid formation of a reduced condition. Bloomield (1953, 1954) reported that aqueous leaf extracts reduced Fe(III) into Fe(II) in soils. The mobilization of iron and manganese due to redox conditions and subsequent formation of iron- and manganese-organo chelates, has been reported to give rise to formation of iron-B, followed by manganese-B horizons in paddy soils (Tan, 1968). In tidal loodwater zones, reduction processes play a considerable role in formation of sulfur-rich soils, as discussed in earlier publications (Tan, 2000). Soils with different redox conditions may also react differently upon N fertilization. In well-drained soils, ammonium-N is subject to nitriication and converted into nitrates (NO3–). However, if the ammonium

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

fertilizer is applied to a reduced soil, such as to paddy soils, it remains available as ammonium (NH4+). For more details on the redox system and redox potentials in soils, reference is made to Tan (1998).

.. Inluence of climatic variations on soil-forming processes In the humid tropics of Indonesia, movement of water tends to be downward in the pedon, enhancing leaching of bases and other soil elements released by the rapid decomposition of soil minerals. Under these conditions, laterization or desiliciication has been considered to be the major soil-forming process in the lowlands, provided drainage conditions are favorable (Tan and Van Schuylenborgh, 1961a; Van Schuylenborgh and Van Rummelen, 1955). On the other hand, podzolization has been detected as the process of soil formation at higher altitudes, especially in the highlands or in Mohr’s mountain lands. In between the two zones, a transitional zone exists, earlier called the uplands, where both laterization and podzolization have been noticed to occur simultaneously.

...

Mineralization versus humiication

The zonal divisions of soil-forming processes above are caused by the changing climates with elevation above sea level, yielding differences in the rates of organic matter decomposition. As indicated earlier, in the lowlands, organic matter is observed to be mineralized completely, and only very small amounts of humic substances have been formed. The peculiar picture of a

Chapter ive: Soil Formation, Classiication, and Land Use



tropical soil proile in Indonesia, exhibiting a very thin litter layer (O horizon) on top of the mineral part of the soil, tends to give support to the above. Consequently, one would expect the role of humic substances to also be very minimal, if any at all, in soil formation in the humid tropical lowlands of Indonesia. Because of the rapid mineralization of soil organic matter into CO2, H2O, and other substances, several Dutch scientists were of the opinion that the weathering agent, percolating through the pedon, is therefore mainly water containing CO2 (Hardon, 1936a; Van Schuylenborgh, 1958). Hence, the rate of mineralization of soil organic matter and the rate of diffusion of CO2 gas into the soil and the atmosphere are considered the determining factors for soil formation in the humid lowlands. The produced CO2 dissolves in soil moisture and may form carbonic acid. The reaction may be illustrated as follows: CO2 + H2O → H2CO3

(5.2)

In pure water, the amount of CO2 dissolved generally amounts to 0.984 × 10−5 moles/L, which is based on air, containing 0.03% CO2 (at 1 atm pressure), that is in equilibrium with water. The partial pressure of this CO2 (Pco2) equals 0.29 × 10−3 atm. The value of Pco2 in soil air is expected to be somewhat higher than in ordinary air because of production of additional CO2 due to mineralization, respiration of roots, and microbial activity. For the chemical calculations using Henry’s law, reference is made to Tan (2000). Dissolved carbon dioxide, CO2, affects many biological and chemical reactions in soil. It is used by aquatic



Soils in the Humid Tropics and Monsoon Region of Indonesia

plants, such as algae, in photosynthesis (Tan, 2000). It is chemically active and interacts with soil moisture to form carbonic acid as indicated above and hence may affect the soil pH. Carbonic acid is a weak acid and will dissociate some of its protons, as indicated by the reaction below: H2CO3 ← → HCO−3 + H+

(5.3)

By applying the mass action law, Van Schuylenborgh (1958) reported the following relationship to be valid: (HCO−3 )(H+ ) = 3.5 × 10−7 k= (H2CO3 )

(5.4)

He then calculated, with Equation 5.4 and Henry’s law, the pH values of soil moisture at different levels of Pco2 and came to the conclusion that at Pco2 = 0.25 × 10−3 atm, the soil pH = 4.23. The partial pressure above is close to that of a normal CO2 content in air in contact with water. Once again, for detailed chemical calculations, reference is made to Tan (2000) and Van Schuylenborgh (1958). Though the value of PCO2 in soil air was considered higher due to respiration of plant roots and microbial activity, it can nevertheless be argued that the litter layer (O horizon) of soils in the lowlands of Indonesia is often very thin. This condition makes possible a rapid exchange of the produced CO2 with the atmospheric air above by diffusion. Consequently, the partial pressure of CO2 is expected not to rise signiicantly above 0.25 × 10−3 atm in soil air, with the result that the pH of the percolating water is still around 4.23 to 4.0. This is

Chapter ive: Soil Formation, Classiication, and Land Use



then the main weathering agent, which has an acidic strength similar to that of weak acids. At higher elevations, or in the highlands of Indonesia, quite different processes are taking place. Due to the prevailing cooler climate, chemical activities are somewhat subdued. The litter layer (O horizon) tends to be better developed and is often considerably thicker than that in the lowland soils. Consequently, more humus is expected to be formed. Oxidation of soil organic matter will also be less intensive, whereas mineralization tends to be replaced by humiication processes. The weathering agent is, therefore, soil moisture, containing high amounts of humic substances and other organic acids. It appears that these organic compounds are playing a greater role in soil formation than carbonic acids, especially at altitudes of 1000 m above sea level or higher. Therefore, in the humid tropical highlands, podzolization is considered as the main soil-forming process. The effects of humic acids in soil formation, and especially in translocation of clays (illimerization) and of aluminum and iron, resulting in formation of albic and spodic horizons, have always attracted a lot of research attention (Aarnio, 1913; Bloomield, 1953, 1954; De Coninck, 1980; Gallagher, 1942; Jones and Wilcox, 1929; Tan, 1986; Van Schuylenborgh and Bruggenwert, 1965). The principles of mobilization and immobilization of aluminum and iron as a result of chelation by humic acids have also been suficiently discussed in the sections above. In the monsoon zones, the soils are affected by a seasonal alternating water movement. During the wet season, water may percolate downward, favoring laterization to take place in the lowlands. Laterization is still



Soils in the Humid Tropics and Monsoon Region of Indonesia

the main soil-forming process, especially in regions with very short dry seasons. It is also noticed that the process can proceed to higher altitudes in the monsoon regions. Whereas in the humid tropics, laterization is pronounced only at altitudes of ≤600 m above sea level, in the monsoon regions laterization is still detected at 1000 m above sea level. In monsoon areas, where the dry season is especially longer and sharper, water movement tends to be upward during the dry season, and because of this, some calciication processes are more likely to accompany the process of laterization. Calciication is noticed to become more pronounced in monsoon regions with very long dry seasons. This is then the reason why the soils in the monsoon zones are less acidic in reactions than the soils in the constantly humid areas. From the discussion above, the conclusion can be made that the condition in the humid highlands approaches that of a cool humid climate in temperate regions, where humiication is believed to be more important than mineralization. This can be supported perhaps by the data in Table 5.1, showing organic matter content and its C/N ratio in a temperate region soil versus soils of the highlands and monsoon regions of Indonesia. The C/N ratios of the gray-brown podsolic soil in the humid tropics of the Indonesian highlands compare favorably with those of its counterpart soil in the United States. The data indicate that these ratios decrease with depth in the proile, meaning that organic decomposition products richer in nitrogen have been produced (that is, humic substances). However, a different trend was observed in the brown podzolic soil

Chapter ive: Soil Formation, Classiication, and Land Use



Table 5.1 Organic C Contents and C/N Ratios of Temperate Regions and Indonesian Soils Gray-Brown Podzolic Soil (Alfisol), USAb

Gray-Brown Podzolic Soil (Alfisol), Humid Tropicsa

Brown Podzolic Soil, Monsoona

Hor. %Cor C/N

Hor. %Cor C/N

Hor. %Cor C/N

A

—

14.0

A

9.45

12.6

A

12.0

18.7

E

—

—

E

7.19

9.2

—

—

—

B

—

10.1

Bt1

5.45

7.9

Bt1

7.84

16.9

C

—

7.6

Bt2

2.73

6.3

Bt2

7.65

21.4

a

b

From Tan, K.H. and Van Schuylenborgh, J. (1961a) and Van Schuylenborgh, J. and Van Rummelen, F. F.F. (1955). From Anderson, M.S. and Beyers, H.G. (1934).

of the monsoon regions in Indonesia. The C/N ratio is noticed to decrease slightly from A to Bt1 horizons, to increase again in the Bt2 horizon. The old terms in soil classiication have been used above, because no name is available in the U.S. Soil Taxonomy system that compares closely to the brown podzolic soil of the Indonesian monsoon region.

..

Inluence of parent materials on soil formation

Results of investigations indicate that the parent material plays a very important role in soil formation in Indonesia (Tan and Van Schuylenborgh, 1961a; Van Schuylenborgh, 1957, 1958; Van Schuylenborgh and Van



Soils in the Humid Tropics and Monsoon Region of Indonesia

Rummelen, 1955). It appears that on andesitic volcanic material quite different soils have been formed than on dacitic or liparitic materials under similar climatic conditions. Tan and Van Schuylenborgh (1959, 1961a) have detected formation of predominantly latosols, the current oxisols, on intermediate parent materials, such as andesitic tuffs. In contrast, red-yellow podzolic soils (the ultisols of today) were found on liparitic tuff, which is classiied as an acidic parent material (see Chapter 2 for deinitions of the geologic terms). Both observations were valid for the lowlands under similarly constant humid climates. Compared to the ultisols of the southern region of the United States, the Indonesian ultisols and oxisols are relatively much younger in age. The American ultisols were formed after the latest ice age, the Wisconsin Ice Age, which is equivalent to the Würm Ice Age of Europe. Accordingly, they are not more than 25,000 years old. The soils in Indonesia originate from volcanic deposits of late Holocene to subrecent geologic age, which is estimated to be about 12,000 years old. It can be further argued that the Indonesian soils most likely do not represent inal stages in their process of formation but are transitional forms to other soils. In addition to the above, the prevailing higher temperatures in Indonesia induce a more rapid weathering process to occur than in the temperate region zones of the United States. As discussed earlier, the average annual temperature in Indonesia may luctuate from 13 to 20°C, whereas this temperature in the United States may vary from 7 to 10°C. This is a difference of about 9°C. The law of Van’t Hoff indicates that the rate of chemical

Chapter ive: Soil Formation, Classiication, and Land Use



reaction increases two- to threefold with an increase of 10°C in temperature (Tan, 2000). Hence, it is perhaps warranted to conclude that in Indonesia a certain stage in soil formation would be reached in only one-half to one-third of the time of that required in temperate regions. The faster rate of weathering and soil formation is supported by the following facts. On August 26 and 27, 1883, a disastrous eruption of the Krakatau volcano in the Sunda Strait occurred. Enormous quantities of volcanic dust were ejected in the air, covering neighboring Lang Island with volcanic deposits of more than 30 m in thickness. Forty-ive years later, on October 31, 1928, Versteegh discovered a soil proile with a surface soil of 35 cm in thickness. In addition to the rate of weathering as discussed above, an important factor affecting soil formation is the intensity of weathering, which is also entirely different between Indonesia and the United States. The issue of weathering intensity is especially important for soil formation in the mountain zones of Indonesia, where humiication plays a signiicant role in the decomposition of soil organic matter (see next section).

.. Precipitation and evaporation ratio and weathering intensity The conclusion was made in the preceding section that soil formation was also affected by the intensity of the weathering process, which particularly affects soil formation in the mountains of Indonesia. The issue is closely related to the strength of the soil solution. The concentration of the liquid percolating through the



Soils in the Humid Tropics and Monsoon Region of Indonesia

parent material in Indonesia is believed to be much lower than that in temperate regions. This is perhaps caused by a dilution of the leaching solution due to the fact that precipitation always exceeds evaporation in the humid tropics as compared to the temperate regions. In Indonesia, the evapotranspiration of a mountain forest in West Java is estimated to be 860 mm of water per year (Coster, 1937), which is considerably lower than the amount of annual precipitation. Because North Sumatra has a comparable humid climate as West Java, its evapotranspiration igure is reported to be the same. However, the evapotranspiration value in East Java is reported to be somewhat higher due to the presence of a monsoon climate. Nevertheless, when the average is taken, the mountain soils in Indonesia as a whole have been formed in climates exhibiting a rainfall/evapotranspiration ratio of 3:6. In the temperate regions, this ratio of precipitation/evapotranspiration is entirely different. For instance, the zone of podzolic soils, and in particular of the alisols (gray-brown podzolic soils), in the United States (Beyers et al., 1935) lies in a belt, in which the precipitation/evaporation ratio luctuates between 1.1 and 1.5. This ratio is perhaps a little on the high side, because the evaporation index used includes data of evaporation from a free water surface and hence does not represent the loss of water by evapotranspiration of a natural forest vegetation. Nevertheless, a trend can be noticed that the ratio is substantially smaller in the United States than in Indonesia. The conclusion may then be drawn that dilution of the weathering solution is much greater in Indonesia than in the United States. Therefore, weathering intensity is expected to



Chapter ive: Soil Formation, Classiication, and Land Use

be much smaller in Indonesia but considerably greater in the United States. This difference explains the fact why in Indonesia the same soils as in the United States can be developed from more acidic or from less basic parent materials. The following examples are given to illustrate the differences in effect of the strength of the leaching soil liquid on translocations of aluminum and iron in Indonesian and temperate region soils. The data in Table 5.2 compare the mobilities of aluminum and iron, as expressed by the molar ratios of Al2O3/Fe2O3 in soils of Indonesia and the United States. As can be noticed, this ratio is relatively constant with depth in the proile of a latosol (oxisols), soils formed by laterization. Table 5.2 Molar Al2O3/Fe2O3 Ratios of Selected Soils in Indonesia and the United States Latosols (Oxisols)a Horizon

Red-Yellow Podzolic Soils (Ultisols)a

Gray-Brown Podzolic Soil (Alfisols)a

Alfisols (Miami Silt Loam)b

Al2O3 Fe2O3

Horizon

Al2O3 Fe2O3

Horizon

Al2O3 Fe2O3

Horizon

Al2O3 Fe2O3

A1

5.50

A/E

5.28

A1

4.75

A1

4.68

A2

5.17

Bt1

5.32

E

5.85

E

4.55

A3

5.13

Bt2

6.10

Bt1

7.47

B

3.19

AC

5.09

C

8.90

Bt2

8.26

C

3.38

C

5.39

a

b

From Van Schuylenborgh, J. and Van Rummelen (1955); Van Schuylenborgh, J. (1957, 1958); Tan, K.H. and Van Schuylenborgh, J. (1959). From Beyers, Alexander, and Holmes (1935).

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

As explained earlier, the weathering solution here is composed mainly of water and CO2, which was considered a relatively weak leaching solution for soil formation. However, the Al2O3/Fe2O3 ratio increases from A to C horizons in the red-yellow podzolic soil (ultisols) and the gray-brown podzolic soils (alisols) of Indonesia. This may suggest that translocation of aluminum is greater than that of iron compounds. The solubility constants (pK value) of aluminum and aluminum– organic complexes are generally smaller than those of iron and iron–organic complexes. At a pK = 32.0, the concentration of soluble Al3+ is calculated by Tan (1998) to be 1 × 10−2 moles/L. It agrees with the concept that strongly acidic soils (pH = 4.0) contain large amounts of aluminum. When similar calculations were made by Tan (1998) for amorphous Fe(OH)3, an Fe3+ concentration of 1 × 10 –8.2 moles/L was obtained for a soil with a pH = 4.0. This supports the allegations above that iron is more insoluble than aluminum. Consequently, aluminum and aluminum–organic complexes may move earlier down the pedon than iron–organic complexes (Tan, 1998; Van Schuylenborgh, 1966). When the alisol (Miami silt loam) of the United States is examined (Table 5.2), a quite different trend can be noticed. The Al2O3/Fe2O3 ratios decrease with depth in the soil proile, which can only mean that iron is made more mobile than aluminum. The latter is believed to happen only when other agents are present in concentrations capable of producing a stronger leaching solution for chelating more iron. Due to the general presence of humiication processes in the temperate regions, the concentration of the soil solution percolating through

Chapter ive: Soil Formation, Classiication, and Land Use



the pedon of the Miami silt loam is apparently higher in humic acid content or other organic substances than in the Indonesian soils.

.

The system of soil classiication in Indonesia

In prewar time, the classiication of soils in Indonesia followed the Dutch concept. A review of the system and the work done in this ield is given by Edelman (1947). After World War II, the system of soil classiication, as developed in the United States, replaced the older Dutch system. At irst, soil classiication based on the zonality concept gained popularity and was soon adapted for use in soil survey and soil taxonomy in Indonesia without or with slight modiications, especially at the universities. This concept grouped the soils into zonal, intrazonal, and azonal groups (Baldwin, Kellogg, and Thorp, 1938; Thorp and Smith, 1949). Using this system of soil taxonomy, the Soil Research Institute at Bogor started in 1955 to undertake a systematic survey of the soil resources in Indonesia. A ive-year working plan was established in this respect in cooperation with the soils division of the FAO-UN. A lot has been achieved, but only a small part of the results has been published (Dudal and Jahja, 1957; Dudal and Supraptohardjo, 1957). The zonality system above was later changed somewhat by Supraptohardjo (1961), who presented a revised system based on soil morphology. The use of soil proiles in the identiication of soils was believed to be able to eliminate the many dificulties encountered in



Soils in the Humid Tropics and Monsoon Region of Indonesia

soil survey and mapping. The modiication places a lot of emphasis on proile characteristics as shown in Table 5.3, whereas elements of soil genesis or soil-forming factors failed to be considered. With the progress in education starting in the 1960s, many Indonesian scientists sent to universities and research institutions in the United States with the Kentucky Contract Team (KCT) and Midwestern Universities Consortium for International Activities (MUCIA) projects (see Chapter 1) became exposed to the new U.S. Soil Classiication system. At irst introduced by the USDA Soil Survey Division under the title of th Approximation, A Comprehensive System of Soil Classiication (Soil Survey Staff, 1960), the system was later revised to become the current Soil Taxonomy, A Basic System of Soil Classiication for Making and Interpreting Soil Surveys (Soil Survey Staff, 1975, 2006b). One of the major dificulties encountered in applying the U.S. system in Indonesia should be briely mentioned here. The U.S. Soil Taxonomy is unfortunately very dificult to read not only for many U.S. scientists, but especially for overseas soil experts, whose primary languages are not English. The text is excessively wordy, and overuse of “one of the following,” followed by the many “ors” and “eithers,” with long sentences in between, makes one forget, when reaching the inal words, what the issue was in the beginning. An example is the following: “Organic soils are soils that () have organic soil materials that extend from the surface to one of the following: (a)...., or (b)..., or ()..., and (a)...()...or ()...etc.” (Soil Survey Staff, 1990, p. 39, 2006a). And this example is not the worst. The many choices and selections phrased in one

Chapter ive: Soil Formation, Classiication, and Land Use

Table 5.3 Soil Classiication Used at the Soil Research Institute, Bogor, Indonesia Category

Profile Development

Great Soil Group

A. Organic Soil

Without Profile Development

1. Organosol

B.Mineral Soil

I. Weak (A)C or No Profile

2. Lithosol 3. Regosol 4. Alluvial Soil

II. AC with Prominent A1 or Chernozemic A

5. Grumusol 6. Rendzina

III. A(B)C with Prominent A1

7. Andosol

IV. A(B)C with Color B

V. ABC with Textural B or Color B and High in Bases

8. Brown Forest 9. Noncalcic Brown Soil 10. Red-Yellow Mediterranean Soil

VI. ABC with Latosolic B 11. Latosol VII. ABC with Textural/ Color B and Low in Bases

12. Red-Yellow Podzolic Soil 13. Lateritic Soil

VIII. ABC with Podzol B

14. Podzol

IX. ABC with Prismatic/ Columnar B

15. Solonetz

X. AC/ABC with Gley horizon and Podzol B or Textural B or Textural B or Color B or Prominent A or Saturated with Ca, cs, and sa

16. Groundwater Podzol 17. Groundwater Laterite 18. Gray Hydromorphic Soil 19. Low Humic Gley Soil 20. Humic Gley 21. Planosol 22. Solonchak

Sources: Supraptohardjo, M. (1961); Dudal, R. and Supraptohardjo, M. (1957).





Soils in the Humid Tropics and Monsoon Region of Indonesia

extremely long paragraph are not only mind boggling, but also violate the rules of writing textbooks, journals, or reports. Nonetheless, several of the younger generation of soil scientists tried to apply the new U.S. system in Indonesia but soon realized that it has to be modiied somewhat and adapted to local conditions. The Bogor Soil Research Institute has used a modiied version in revising its Exploratory Soil Map of Indonesia. The 2000version soil map, as shown in Figure 5.1, recognizes in its index the following divisions of soils in Indonesia, listed below by the author in descending order from soils with the largest acreages.

Inceptisols Ultisols Entisols Oxisols Histosols Mollisols Alisols Aridisols Spodosols Vertisols Miscellaneous

Percent (%) of Total Area 38.51 24.27 9.62 7.50 7.01 4.56 2.77 2.55 1.16 1.15 0.90

The total soil acreage is listed as 1,882,102 km2 (Centre for Soil and Agroclimate Research, 2000). As can be noticed, several of the soil orders occur in very small acreages (for example, alisols, spodosols, and vertisols), perhaps for reasons that they are not recognized

Chapter ive: Soil Formation, Classiication, and Land Use



or truly occur only in a limited extent. This will be discussed in later chapters.

.

Land use in Indonesia

The soils above are used in agriculture for the cultivation of food, estate, and industrial crops. The major food crops grown in Indonesia when ranked by acreages are rice, corn (called maize in European countries), cassava, and soybean. As noticed from Table 5.4, the soil acreages under rice far exceed those cultivated by other food crops, with corn second, cassava third, and soybean fourth in importance. Other crops, not stated here, are found in smaller soil acreages than the four above. From the data, it seems that the biggest concentrations of rice cultivation are on the islands of Java and Sumatra, with 5 million and 3 million hectares under rice, respectively (Biro Statistik Indonesia, 1999; FAO-WFP, Table 5.4 Acreages of Major Food Crops of Indonesia (× 1 Million Hectares) Island Rice Corn Cassava Soybean Java Sumatra Sulawesi Kalimantan Bali and N. Tenggara Moluccas and West Papua Total

5.00 3.00 1.20 1.00 0.63 0.04

1.80 0.65 0.45 0.05 0.34 0.10

0.69 0.27 0.07 0.04 0.13 0.02

0.67 0.20 0.06 0.09 0.15 0.03

10.87

3.39

1.22

1.20

Sources: Biro Statistik (1999); FAO-WFP (1999); Fisher, C.A. (1966).



Soils in the Humid Tropics and Monsoon Region of Indonesia

1999). The igures refer perhaps to acreages of lowland rice and to these should perhaps be added the acreages of upland rice cultivation. It is important to note that whenever possible, the people in Indonesia prefer growing lowland rice or rice grown in inundated ields, called paddy-sawah. Most of the sawah ields are located on oxisols, ultisols, inceptisols, entisols, and peat soils (histosols). Rice is a major staple food crop, and the 1999 paddy production was estimated to be 48.6 million tons, an amount not much different from the 48.5 million tons reported for 1998. According to the Biro Statistik, Indonesia had to import in the year 2000 an additional 3.1 million tons of rice to feed its population. The most important estate and industrial crops are rubber, oil palm, tea, coffee, cocoa, copra, and spices. A distinction was made by the Agency for Agricultural Research and Development (AARD, 1986) to divide the nonfood commodities into industrial and estate crops. Crops produced by large plantations owned by the government or large companies are classiied as estate crops (for example, tea, coffee, cocoa, and oil palm). All other crops produced by smallholders, owned by small farmers, are called industrial crops (for example, coconut [copra], iber crops, and spices). The rubber oil palm and coconut palm estates, for the production of copra, are generally found in lowland areas, where the climate is most suitable for growing these plants. On the other hand, tea, coffee, and cocoa estates are usually cultivated in the upland and highlands of Indonesia. They are considered mountain crops, and the best tea and coffee plantations are found in the cool mountain climate of Indonesia. Tea requires a cool humid tropical

Chapter ive: Soil Formation, Classiication, and Land Use



Af climate, and hence, most of the tea plantations are in the mountains of Sumatra and West Java. On the other hand, coffee is more adapted to a cool monsoon Am climate of the mountains of East Java. The name Java Coffee is derived from this island. Another important estate crop is sugarcane, whose cultivation is limited to lowland areas with an Ama climate. This type of climate is found in the lowlands of East Java where most of the sugarcane estates are therefore located. The soils are the vertisols with poor physical properties. Indonesia is also known as the spice islands, and these spices were the reasons for the Portuguese and Dutch companies to venture east in the early days of the 1500s and 1600s. The major crops producing spices, cultivated in Indonesia, include pepper (Piper nigrum), clove (Eugenia caroyphyllata or aromatica), and nutmeg (Myristica fragans). Pepper plants are vines and are mostly grown by smallholders in the Lampung lowland of South Sumatra and on the islands of Bangka and Belitung. The pepper fruits, in the form of kernels, are processed into black and white pepper, respectively, for marketing. The inal product is locally called collectively merica or lada. White pepper is the specialty of the Bangka islands, whereas black pepper is produced in the Lampungs. The clove trees were orginally grown in the Mollucas, but the cultivation was extended to West Java in the late 1960s due to soaring demands for cloves by the domestic cigarette, called kretek, industry. However, during the 1990s, clove cultivation seemed to wind down again due to unfavorable government interference and because of import competition from Zanzibar, Africa. The trees are grown in West Java primarily in the lowlands on ultisols and on



Soils in the Humid Tropics and Monsoon Region of Indonesia

upland andosols. The lower buds are harvested green and dried to produce the brown-colored cloves, locally called cengkeh. Nutmeg (locally known as pala) trees are also grown originally in the Molluccas, but as is the case with cloves, its cultivation has been extended to other islands of the Indonesian archipelago. The fruits are very tangy and sour in taste and the large pits or seeds inside the fruits yield after proper drying the nutmegs (called biji pala; biji = pit), whereas the membrane or leece enveloping the nuts is producing the nutmeg mace (locally known as kembang pala; kembang = lower). More details on the cultivation and regional importance of major agricultural crops will be provided in the soil sections.

chapter six

Soils in the lowlands of Indonesia .

Introduction

These are the soils that have been formed primarily by laterization processes under the inluence of year-round humid tropical climates. Rapid and drastic weathering processes are dominant, whereas organic matter is usually mineralized into CO2, H2O, and their mineral components. Humiication is of little importance and plays a minor role in soil formation. The major soils, discussed in the following sections, are the latosols, called oxisols, and red-yellow podzolic soils, called ultisols, by the U.S. Soil Taxonomy (Soil Survey Staff, 2006b). These soils tend to occur mainly in Köppen’s Afa types of climates. As will be discussed in the sections below, it is very dificult to compare these soils in Indonesia with those listed in the U.S. Soil Taxonomy; hence, the Food and Agriculture Organization–United Nations Educational, Scientiic, and Cultural Organization (FAO-UNESCO, 2006) and World Reference Base (WRB) for Soil Resources (FAO-UNESCO, 1998) systems are also consulted for proper delineations of the soils 

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

in question. For example, in Indonesia the ultisols can be distinguished into lowland and upland ultisols. As will be discussed, the lowland variety tends to be redyellow podzolic soils deined by acidic parent materials, whereas the upland variety is more the zonal group of red-yellow podzolic soils formed in tension zones where both podzolization and laterization are occurring. These terms of soil-forming processes are currently phased out in the soil science of the United States, but fortunately they are still in use and currently valid in the FAO and WRB systems. Other important soils in the lowland of Indonesia are the red-yellow Mediterranean soils and grumusols, for convenience called lowland alisols and vertisols, respectively. Both soils are typical in their occurrence in Köppen’s Ama climate, a monsoon-type climate different from the year-long humid tropical climate of the oxisols and ultisols. This chapter will also discuss the peat soils that occur extensively in the coastal regions of Indonesia, which are called histosols by U.S. soil scientists but are named tropical peat soils by FAO-UN scientists (Andriesse, 1988). The soils have recently attracted worldwide attention due to their reclamation for food and timber production. The disastrous deforestation in the efforts above and the ensuing damaging wildires have alarmed the regions in Southeast Asia.

.

Oxisols

This group of reddish-colored soils of Indonesia, formerly known as latosols, has received considerable attention. They are conined to the tropics (Beinroth,

Chapter six: Soils in the Lowlands of Indonesia



1973), and many ideas concerning their genesis and classiication were suggested (Edelman, 1950; Harris, 1963; Kellogg, 1949; Prescott and Pendleton, 1952). Many arguments and objections still exist concerning its nomenclature. Names such as terra roxas have been suggested (Beinroth, 1973), and many other names were introduced for this group of soils, some akin or related to the term latosols, and others only stressing the kind of presumed soil-forming process that may have taken place (Aubert, 1954; Cline, 1955; Harris, 1963; Mohr and Van Baren, 1960). The U.S. Soil Taxonomy has completely deleted the term latosols in favor of oxisols (Soil Survey Staff, 1975, 1990). All of them seem to have the effect in making the problem even more complicated. The name laterite was irst used for this group of soils, as introduced by Buchanan in 1807 (see Prescott and Pendleton, 1952), and from which the term laterization is derived for the weathering and soil-forming processes of this soil. This has led to the development of names such as laterites, lateritic soils, and latosols. Generally, it is accepted that the process of formation of this kind of soil involves the removal of silica, alkali, and alkaline earth with the consequent concentration of iron and aluminum oxides and their hydrated forms. The latter was discussed in Chapter 5. In Indonesia, this group of soils occupies most of the lowlands, especially in Java. On the other islands, these soils do not seem to be very important, and their occurrence seems to be limited to small areas or regions—in South Sumatra (Lampung province), in West Sumatra (Padang and surroundings), in the southeastern corner of Kalimantan, in South Sulawesi, and in North



Soils in the Humid Tropics and Monsoon Region of Indonesia

Sulawesi (Minahassa province). For more details about the distribution of these soils, see the Exploratory Soil Map of Indonesia (Figure 1.2). If one would consult prewar reports (Mohr, 1938), a far greater distribution of latosols (or oxisols) in the Indonesian archipelago than is stated above would be noticed. This problem will be addressed in more detail in the following pages.

..

Parent materials

The latosols (oxisols) in Indonesia are derived from a wide variety of parent materials. They have been formed from basic to intermediate materials, such as quaternary andesitic volcanic tuff, volcanic lahar, and river deposits or Miocene sediments, provided good drainage conditions prevail. Tertiary materials have formed soils, usually classiied as ultisols (red-yellow podzolic soils) by the Bogor Soil Research Institute (Dames, 1955), though their morphological features are similar to those of the latosols. The morphological criterion used to differentiate ultisols from latosols was in the past the quartz content. The Bogor Soil Research Institute thought that in this way mapping problems could be easily solved. The soils containing quartz were mapped as ultisols, and soils without noticeable quartz content were identiied as latosols. However, that this action creates a lot of confusion is apparent. The central concept of latosols (oxisols) does not exclude the existence of quartz in the soil. True latosols (or the current oxisols) may, in fact, contain quartz (Soil Survey Staff, 1960, 1975; Harris, 1963). Latosols, which morphologically do not exhibit quartz, contain appreciable amounts of quartz in their

Chapter six: Soils in the Lowlands of Indonesia



sand fractions when analyzed by petrographic means (Table 6.1). This separation of latosols from ultisols, based on the quartz content, is one of the reasons why the distribution of latosols (oxisols) in Indonesia is not as large as would have been expected from prewar reports. Many of the soils, which could have been classiied as oxisols, are now mapped as ultisols by virtue of the quartz content. The latosols in the lowlands, from Bogor to the coastal plain of Jakarta, originate from parent materials produced by recent quaternary eruptions of the Salak and Pangrango-Gedeh volcanoes. This andesitic volcanic material stretches northward as a volcanic fan from the foot (±600 m above sea level) of the above-stated mountains to the plain of Jakarta (Verstappen, 1953). According to Verbeek and Fennema (1896), this volcanic fan can be divided into two sections: a younger section and an older section. The existence of such a separation is supported by results of petrographic (Table 6.1) and particle size distribution analyses (Table 6.2). The younger section, which is andesitic tuff and exhibits a hypersthene to hypersthene-augite association (Tan and Van Schuylenborgh, 1959), occupies the area of Bogor northward to regions located at elevations of 100 to 150 m above sea level. From here onto the plain of Jakarta, the older section is found, which was determined as dacitoandesitic, a more siliceous material than the younger andesitic volcanic tuff. The division line can be drawn at the Ciluar proile, where the quartz content of the sand fraction suddenly increases (Table 6.1), and where the particle size distribution of the soil also changes abruptly (Table 6.2). Other indications for the more

17

29

13

13

46

21

22

19

35

A3

B1

B2

C

A1

A3

B1

B2

Magnetite

A1

Horizon

Table 6.1

tr

3

3

4

3

3

2

2

1

Quartz

9

6

2

3

3

8

15

4

5

Iron Concretion

Zeolite

Hydrargillite Volcanic Glass

Plagioclase

Hornblende Augite

—

—

tr

—

1

—

—

tr

—

—

5

7

5

10

5

19

10

7

17

24

—

tr

2

2

tr

—

—

—

—

1

—

—

tr

—

1

tr

tr

1

1

3

4

2

15

4

12

tr

tr

1

tr

1

1

3

7

—

2

4

5

—

Brown Latosol, Bogor (West Java), ±300 m above Sea Level

—

1

1

—

—

Brown Latosol, Pasir Muncang (West Java), ±400 m above Sea Level

Silicon Organic

1

7

11

11

10

5

7

5

12

Hypersthene

Mineralogical Composition of Total Sand Fraction of Oxisols

—

—

—

—

—

—

tr

—

—

Olivine

1

5

5

1

—

1

4

2

1

Stone Fragment

50

41

45

39

14

51

43

26

27

Miscellaneous

 Soils in the Humid Tropics and Monsoon Region of Indonesia

75

31

30

43

50

38

52

51

54

35

51

57

54

41

A1

A2

B1

B2

B3

A1

A2

B1

B2

A1

A2

B1

B2

B3

17

12

17

18

22

5

12

8

10

6

12

7

2

16

—

—

—

—

—

20

20

17

2

2

—

6

5

3

1

2

7

4

tr

—

—

—

—

—

—

2

3

7

1

1

1

1

tr

1

tr

1

2

—

—

—

—

tr

3

9

10

—

1

—

2

—

—

—

—

—

tr

—

2

Red Latosol, Cibinong (West Java), ±100 m above Sea Level

2

—

—

tr

—

3

1

3

7

8

tr

4

16

25

36

23

14

10

18

—

—

—

—

tr

1

1

—

1

—

—

—

—

—

—

—

—

2

2

7

—

—

tr

2

1

—

—

—

—

—

—

tr

—

—

5

—

—

tr

3

1

Red Latosol, Passar Minggu (West Java), Plain of Jakarta, ±50 m above Sea Level

18

12

10

9

15

14

6

8

tr

Reddish-Yellow Latosol, Ciluar (West Java), ±150 m above Sea Level

—

—

—

—

—

—

—

—

—

4

—

—

—

—

3

5

6

8

5

2

3

3

7

20

3

4

1

—

2

2

5

4

5

6

18

14

9

12

20

20

17

Chapter six: Soils in the Lowlands of Indonesia





Soils in the Humid Tropics and Monsoon Region of Indonesia

Table 6.2 Particle Size Distribution of Latosols (Oxisols) Soil

Percentage 22°C; f = humid; h = annual temperature >18°C; i = difference between coldest and warmest months 50 µ fraction) and higher in clay content than the younger brown oxisols. In the redcolored soils, the sand content may even drop to 18°C; a = warmest month >22°C; f = humid.

1.6

Afa

36

1921

Tanjung

Kalimantan

8.4

920

Parapat 2.2

A Afa

3130

11.0

0.2

400

Pematang Siantar

Pakanbaru

A

A

A

Afa

Afa

Afa

2870

North Sumatra

10.9

2379

S&F

10.4

0.5

10.0

Köppen

Type of Climatea

0.5

90

Jasinga

1.1

mm

Mean Annual Rainfall

Bantam (West Java)

Months

100 mm

Rainfall

6

15

m

Rangkasbitung

Location

Altitude

Table 6.9 The Climate of Red-Yellow Podzolic Soil (Ultisols) Areas in Indonesia

Chapter six: Soils in the Lowlands of Indonesia





Soils in the Humid Tropics and Monsoon Region of Indonesia

soil exhibits an almost similar morphology as red latosols. The keys to the U.S. Soil Taxonomy seem to support the latter, because no E (albic) horizons are stated as characteristic horizons of ultisols (Soil Survey Staff, 2006a, p. 33). When the text is consulted and after wondering about the proper choices following the several “eithers” and many “ifs” and “ors,” the conclusion can be made that only an argillic (Bt), a kandic, and a fragipan are the three major horizons characterizing a proile of ultisols. No mention is made about base saturations. An example of a proile description of a red-yellow podzolic soil of Indonesia itting the U.S. Department of Agriculture (USDA) morphological concept in general is as follows: Red-yellow podzolic soil, in the lowland (100 m above sea level) of Bantam, West Java; topography: gently rolling hills; vegetation: dense tropical lowland forest with underbrush composed of bushes and grass. The proile is located on the top of a low hill, with moderately well-drained conditions. Horizon Depth (cm)

Description

A

0–10

10YR 5/6 (ield moist), yellowishbrown, silty clay loam, strong granular to moderate ine subangular blocky, friable.

Bt1

10–40

7.5YR 5/6, strong brown, clay, moderate ine subangular blocky, faint clay/iron coatings, friable.

Chapter six: Soils in the Lowlands of Indonesia



Bt2

40–52

7.5YR 4/6, yellowish-red, clay, moderate medium subangular blocky, friable, iron coatings, some mottles.

Bt3

52–85

5YR 4/8, yellowish-red, clay, moderate, medium subangular blocky, friable, clay and iron coatings, mottles.

Bt4

85–110

5YR 5/6, yellowish-red, clay, massive, slightly irm, mottles.

C

+ 110

10YR 7/2, very pale brown, clay, massive, slightly irm, mottles.

Another proile description, representing the redyellow podzolic soils of West Sumatra, is given below. This proile is located in the experimental ields of the Faculty of Agriculture, University of Andalas, Limau Manis Campus, Padang, Indonesia. The area is located at 350 m above sea level. The soil is derived from dacitic tuff, is well drained, and is located on the slope of a small hill. The hilly area is covered by vegetation composed of bushes (for example, Pandanus sp., Diplazium sp., Piper sp., and Imperata sp. grasses). A photograph, illustrating the soil proile above, is presented in Figure 6.7. Horizon

Depth (cm)

Description

Ap

0–15

10YR 4/4, dark yellowish-brown, clay, weak ine blocky, friable, many macropores, lots of coarse and ine roots, diffuse wavy boundary.



Soils in the Humid Tropics and Monsoon Region of Indonesia

Bt1

15–29

10YR 5/6, yellowish-brown, clay, weak medium blocky, friable, abundant macro- and micropores and lots of coarse and ine roots, diffuse wavy boundary.

Bt2

29–65

10YR 5/8, yellowish-brown, clay, weak medium blocky, friable to slightly irm, coarse and ine roots, less macropores but abundant micropores, diffuse, broken, boundary.

Bt3

65–116

10YR 5/6, yellowish-brown, clay, weak medium blocky, friable to slightly irm, some ine roots, less macropores but abundant micropores, diffuse broken boundary.

C

+116

5YR 5/8, yellowish-brown, clay, massive to weak medium blocky, friable, small amounts of roots, small amounts of macropores, lots of micropores, diffuse, broken, boundary.

..

Soil classiication

The taxonomic classiication of red-yellow podzolic soils is apparently less confusing than that of latosols (oxisols). In the U.S. Soil Taxonomy (Soil Survey Staff, 2006a), the soils are placed in the ultisols order, which is deined as a group of soils having argillic, Bt, horizons,

Chapter six: Soils in the Lowlands of Indonesia



Figure 6.7 Red-yellow podzolic soil (ultisol) at the experimental ields of the University of Andalas, Padang, West Sumatra, Indonesia. (Courtesy of Ir. Burhanuddin, former Assistant Dean Faculty of Agriculture, and Ir. Datuk R. Imbang, Soil Scientist, University of Andalas.)

and base saturations 50 µ 50–2 0.9% in the upper 15 cm of the argillic horizon.

...

Charge characteristics

The ultisols (red-yellow podzolic soils) in Indonesia are characterized by low permanent charges (CECp) of the order of 3 to 7 me/100 g or 3 to 7 cmol(+)/kg, with the lower values exhibited by the soils of Kalimantan. The soils are invariably high in free or exchangeable Al contents, but again the red-yellow podzolics of Kalimantan exhibit, comparatively, substantially lower exchangeable Al percentages than the soils in Java and Sumatra (Table 6.12). The variable charges, as expressed by CECv, are somewhat higher, and their values vary only very slightly between the soils of Java, Kalimantan, or Sumatra. However, the CEC at pH 8.2 and the maximum CEC are quite large, showing values twice as high as those of the CECv. Several of the exceptionally high values of CEC8.2 and CECm in the A horizons are contributed by the high organic matter content. The samples, as indicated earlier, were collected from virgin soils under the original vegetation cover. The observations above conirm the opinion that these soils are variable-charged soils and hence may exhibit a chemical behavior upon use and cultivation different from permanent-charged soils (Tan, 2003b). The conclusion for considering these soils as variable charged is supported by the presence of relatively high positive charges, as expressed in terms of AEC (anion-exchange capacity) values, ranging from 8 to 14 me/100 g or 8 to 14 cmol/kg soil. The exception is in the ultisols of Kalimantan, derived from granite,



Soils in the Humid Tropics and Monsoon Region of Indonesia

Table 6.12 Ultisols Soil

Charge Characteristics of

A13+ CECp CECv CEC8.2 CECm

Humid Tropics

AEC

cmo1(+)/kg

Red-Yellow Podzolic Soil, Bantam, West Java A

4.6

5.45

7.75

13.20

16.24

8.42

E

4.3

5.60

7.85

13.45

15.30

9.28

Bt1

6.2

6.10

10.30

16.40

20.50

11.46

Bt2

6.2

6.00

9.00

15.00

19.13

10.60

Red-Yellow Podzolic Soil, Aceh, North Sumatra A

2.8

7.06

7.26

14.32

19.20

3.94

Bt1

4.1

6.76

7.07

13.83

9.32

3.74

Bt2

5.8

5.36

13.57

18.39

7.38

3.33

Red Podzolic Soil, Kalimantan A

1.3

3.85

17.02

20.87

28.82

12.53

E

0.7

3.13

9.25

12.38

21.94

12.35

Bt1

1.1

4.34

9.77

14.11

20.63

13.53

where AEC values are in the range of 3 to 4 me/100 g or 3 to 4 cmol/kg soil.

...

Clay mineralogy

Differential thermal analysis (DTA) of the clay fractions shows a mixture of 1:1 type of clay minerals, gibbsite, and the dominant presence of amorphous or noncrystalline clays. This observation is in support of

Chapter six: Soils in the Lowlands of Indonesia



considering the soils as variable charged. The presence of some 2:1 clays, as reported from x-ray diffraction analyses by Van Schuylenborgh (1957), is less obvious by DTA. Smectite, when present, creates serious issues in the prevailing concepts of ultisols in the United States, where kaolinite is believed to be the characterizing clay mineral (McCaleb, 1959; Rich and Obenshain, 1955). Simonson (1949) also suggested the use of smectite as the distinction between ultisols (red-yellow podzolic) and alisols (gray-brown podzolic soils). The soils containing kaolinitic clay minerals are, in his opinion, ultisols, whereas soils with smectite in their clay fractions should be called alisols. The noncrystalline or amorphous clays are shown in DTA by the combination of very sharp low endothermic (±200 C) and very sharp high exothermic peaks between 900 and 1000 C (Figure 6.8). X-ray diffraction analyses of the ultisol clays, yielding weak diffractograms or curves with very weak low-intensity peaks (Figure 6.9), support the presence of large amounts of amorphous, noncrystalline, or short-range-order clay minerals (Goenadi and Tan, 1989). This is in sharp contrast with the XRD curves of the oxisols, showing sharp high-intensity peaks at 0.712 and 0.359 nm for the presence of crystalline clays (e.g., kaolinite). This mineral is, however, also considered a variable-charged clay mineral. Its permanent charge is relatively small due to the small amount of isomorphous substitution in the tetrahedral and octahedral positions. Most of the negative charge in kaolinite originate more from dissociation of the H– ions of exposed octahedral-OH groups, a process which is also soil pH dependent. Therefore, the electronegative charges of



Soils in the Humid Tropics and Monsoon Region of Indonesia

1 2

3

4

1000

800

600

400

200

5

°C

Figure 6.8 Differential thermal analysis (DTA) thermograms of red-yellow podzolic soil clay fractions: (1) A and (2) Bt Horizon, Aceh, North Sumatra; (3) Bt Horizon, Kalimantan; (4) Bt and (5) C Horizon, Bantam, West Java.

kaolinite will also rise and fall depending on soil pH values. Nevertheless, some of the soil scientists disagree with the above and are of the opinion that kaolinite, as is the case of smectite, does not possess pH-dependent charges unless aluminous impurities are present (De Villiers and Jackson, 1967; Fiskell and Perkins, 1970).



Chapter six: Soils in the Lowlands of Indonesia 1.402 nm ULTISOL 0.369

B 11

0.719

0.444

0.712 nm

0.359

A

OXISOL 0.444

28

A

20

B

2θ

12

3

Figure 6.9 X-ray diffraction (XRD) spectrograms of A and B horizons of clay fractions of ultisols (Bantam, West Java) and oxisols of Indonesia. (From Goenadi, D.H. and Tan, K.H., [1989].)

..

Land use and evaluation

...

Evaluation of analytical properties

As indicated earlier, the ultisols are perhaps the most widely distributed soils of Indonesia. The total area with ultisols far exceeds the total acreage of the oxisols in the archipelago. The soils cover most of the lowlands in Sumatra, Kalimantan, Maluku, and Papua. In Java, the ultisols occur mostly in Bantam and perhaps also at higher elevations in the tension zones.



Soils in the Humid Tropics and Monsoon Region of Indonesia

However, in contrast to oxisols, the ultisols in Indonesia generally exhibit poor physical and chemical properties. Most of the soils are relatively heavy-textured soils but possess a low degree of stable aggregation, which often results in low permeability. These properties tend to make them very sensitive to severe erosion. Drastic weathering and high leaching have also resulted in strongly to very strongly acid conditions, with pH values often exhibited one unit below those of the oxisols. Most of the nutrients have also been transported to deeper layers. However, because the base saturation in the subsoil is less than 35%, the amount of nutrients held is most likely inadequate for plant and crop growth. In addition, at a depth of 1 to 2 m, the nutrients may be relatively out of reach to shallow-rooted crops. These soils are, therefore, considered to be poor agricultural soils. Similar characteristics have been reported for temperate region ultisols (for instance, in the southern coastal plain of the United States), making these soils infertile unless properly managed (Fiskell and Perkins, 1970; Perkins et al., 1973). However, soil organic matter, nitrogen, available phosphorus, calcium, and especially potassium contents, though generally considered low in surface soils, show considerable variation in Indonesian ultisols. For instance, the ultisols of West Java are comparatively more fertile than their counterparts on the other islands. Due to their location in the mountain range of Java, these ultisols have experienced from time to time some kind of a rejuvenation process in the form of nutrient-rich andesitic ash showers. Worth mentioning are the ultisols in Sumatra and the Moluccas, which are rich in potassium. The ultisols in Sumatra

Chapter six: Soils in the Lowlands of Indonesia



are developed mostly from liparitic tuff, relatively rich in feldspar, biotite, and muscovite (Van Dijk, 1952). These minerals are important sources of potassium for perennial crops, such as rubber and oil palm, which are extensively grown in the lowlands of Sumatra. This is especially true for the younger members or soils that have received rejuvenation in the recent past in the form of volcanic ash showers. The ultisols in the Moluccas originated from schists, rich in micas, and are therefore also rich in potassium. Nevertheless, the ultisols of both Sumatra and the Moluccas may still have the poor physical properties exhibited by ultisols in general (Tan et al., 1963, 1965). To the above should perhaps be added that in virgin conditions where the vegetation cover is still present, the ultisols in Indonesia may still have high amounts of organic matter in their surface layers, as can be noticed from the data in Table 6.11. In addition, the nutrient content of the soil surface is often maintained at adequate levels for proper plant growth by the process of nutrient cycling. But as soon as the area is deforested and the soil cultivated for as little as 1 year, the available nutrient supply of the soil surface is soon exhausted.

...

Signiicance of basic soil properties

The properties related to low degree of aggregate stability and low pH have to be corrected when erosion hazards are to be decreased. Chemically, this can be achieved by liming the soils properly, a process by which not only the soil pH can be adjusted to the desired level for proper crop production but will also increase or enhance aggregation of soil particles. Good

00

Soils in the Humid Tropics and Monsoon Region of Indonesia

aggregation of soil particles is required for the development of soil structures, which in turn promotes the formation of pore spaces, beneicial in improving soil permeability. In addition, the application of organic matter, compost, green manuring, and other types of soil-structure-enhancing processes may be performed alone or in combination with the above. The application of soil amendments, such as phosphogypsum and other soil stabilizers, is considered by some scientists an alternative method to traditional procedures for control of erosion (Levy, 1995). As the soil pH is increased by liming procedures, the variable charges, arising from soil organic matter and the highly weathered clay, are also increased substantially. The latter, as relected in higher CECv, CEC8.2, and CECm values (Table 6.12), was discussed earlier for enabling the soil to store more nutrients for plant growth. Enlarging the soil CEC is very important, in view of the need to apply fertilizers in controlling the soil’s inherent low nutrient content and in offsetting nutrient losses by leaching and plant uptake. However, as indicated in the aforementioned section, in the fertilization procedure, it should be kept in mind that several of the ultisols are potentially rich in potassium and may not need large amounts of K-fertilizers.

...

Agricultural operations

.... Shifting cultivation Most of the area covered by ultisols is located on the rather thinly populated islands of Sumatra, Kalimantan, Sulawesi, and Papua. Because in this case large areas of lands are available, shifting cultivation is often practiced. This method is

Chapter six: Soils in the Lowlands of Indonesia

0

locally called the ladang or huma system and is often erroneously considered synonymous with the slashand-burn method. By deinition, shifting cultivation involves complex cycles of processes that allow lands to lie fallow for some time after cultivation and recover before again being slashed, burned, and cropped. Commonly, a family or unit of settlers functions collectively in clearing the forest. They then claim customary rights over the particular stretch of territory that was cultivated, often amounting to 50 km2 or more, which was referred to in Chapter 1 as tanah adat. This method of shifting cultivation, practiced mostly in the tropical rain forest, has attracted worldwide attention due to an allegedly massive deforestation. However, when conducted properly, it encourages at the end of the cycle the growth of a secondary forest and hence will result in minimal ecological damage. Slash-and-burn is only part of it and can be practiced on its own without the necessary cycles of fallow followed by development of a secondary forest stand. The method is practiced lately in close relation to the Indonesian government transmigration program for a rapid clearing of the forest and production of enough food for the migrant settlers during their irst years, ensuring in this way the success or failure of the resettlement program. Due to violent conlicts in the 1990s between the settlers and indigenous people (see Chapter 1), and because of the Asian inancial crisis in August 2000, large-scale transmigration programs have now been cancelled. Slash-and-burn was, in fact, also conducted in temperate-region forests of Northern Europe, where it was known by different names (for example, swidden,

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

assarting, and svedjebruk). On its own, it is a very controversial method, and many scientists consider it harmful to the ecology. The issue of slash-and-burn is exacerbated when the method contributed since 1990 to the deforestation of lands of more than 40,000 ha annually in Colombia for the cultivation of crops, producing illegal drugs, such as marijuana and coca. It has also received worldwide attention with the disastrous lareups of wildires, destroying in 1997 and 1998 parts of the peat forest in south Kalimantan. Thick, toxic smoke from these wildires was also covering Medan and Palembang in North and South Sumatra, respectively, and has even spread dangerously over neighboring Singapore and Malaysia, forcing temporary closures of their airports. In shifting cultivation, most of the trees and other types of vegetation are cut and left to dry. Parts of the timber are collected and used as building material, whereas another part may be used as irewood or for making charcoal. As soon as the residual vegetation is dry, it is burned to clear the soil for cultivation. In view of the strongly acidic reaction and low nutrient contents of ultisols, the ash proves to be temporarily beneicial in increasing the soil pH and supplying nutrients. The cleared plots are usually cultivated with upland rice, maize, or root crops—for example, cassava (Manihot utilissima) and banana (Musa paradisiaca) or other fruit trees. Recently, hot pepper plants (Capsicum annuum or Capsicum frutescens) are becoming very popular as huma crops. Most Indonesian food is very spicy, and hot pepper is one of the main ingredients used to make it hot and spicy. The increasing demand for hot pepper has

Chapter six: Soils in the Lowlands of Indonesia

0

increased its market price often to such a level that it is more proitable growing hot pepper than upland rice in the humas. Intercropping is often practiced, and three stories of crops may then be present, with sweet potatoes, hot peppers, and taro as the “ground-dwelling” crops, whereas cassava, banana, or papaya constitute the middle story, and coconut, jackfruit, and other fruit trees are the upper-level crops. In the heyday of rubber, rubber trees were also favored intercrops. When crop yields decrease after 1 to 3 years, due to a decline in soil fertility, the ields are left fallow, allowing them to return into a secondary forest stand, a cycle vital for this type of cultivation. The banana and other fruit trees are still producing in the secondary forest growth, when cultivation has to shift to a new plot that has been cleared also by the slash-and-burn method. The rubber trees are then also ready to be “tapped.” All these provide a welcome addition either to the diet or to the settler’s income. If the method is carried out properly, the old site can be used again in about 8 to 10 years. The International Center for Soil Research and Agroforestry (ICRAF, personal communications) at Bogor is even of the opinion that ideally 20 years are needed before returning cropping at the irst site. They believe that by giving the land enough time to recover, shifting cultivation can be productive with fewer ecological implications while providing a method of sustainable agriculture in the lightly populated regions of Indonesia. If and when the cycle is too short, this may produce vast areas of wasteland invaded by cochon grass, locally called alang-alang (Imperata cylindrica). The latter is the case in many areas of Sumatra, Kalimantan,

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

and the Moluccas. Setting ire to the dry grasses during the dry season in order to produce young shoots that attract deer and other game animals contributes to the further impoverishment of the ultisols. Natural reforestation needs considerable time and much help on such poor soils. Despite the untidy and sloppy appearance of the cultivated plots, the link between the protective vegetation and preservation of a fertile soil is implicit in shifting cultivation, whereas the use of ash after burning as a source of nutrient supply and avoiding excessive weeding and other drastic cultivation practices are considered by many people eminently sound (Fisher, 1966). .... Rice cultivation Because rice is a major staple food in Indonesia, growing rice has received more attention in the agricultural operations of Indonesia than other crops. As discussed earlier with the oxisols, rice is cultivated in Indonesia by two methods (for example, inundated paddy-ield and dryland methods). The paddy-ield (locally called sawah) method, by which lowland rice is grown in diked and inundated plots of land, is the traditional method. This method is practiced extensively in Java and Bali, where paddyields are dotting the landscape from the lowlands to the mountain regions. In the less densely populated areas of Sumatra, Kalimantan, Sulawesi, and Papua, the paddy-ields are less numerous, though still considered the most important method for growing rice. Therefore, relatively large concentrations of paddy-ields on ultisols seem to be located more near centers of populated areas in Sumatra (e.g., Banda-Aceh, Medan, Padang,

Chapter six: Soils in the Lowlands of Indonesia

0

Jambi, Benkulu, and Lampung). Substantial areas with lowland rice areas are also found in West Kalimantan, Southeast Sulawesi, Maluku, and near Merauke in Southeast Papua. In the surrounding areas of Medan, North Sumatra, and in Solok, West Sumatra, the paddyields produce the Medan and Solok rice, respectively, favored for consumption by local people in Sumatra. Under sawah culture, the soils need fertilization with large amounts of nitrogen, phosphate, and in some ultisols also with potassium. Heavy applications of lime and phosphate (e.g., 1 to 5 tons CaCO3 and 200 to 500 kg triple superphosphate per hectare) have been recommended by Go (1961) to ensure optimum rice yields. The nitrogen used should be applied preferably in the form of urea, because its acidity is only one-third that of sulfate of ammonia. In the absence of additional fertilization, rice yields may be as high as 1700 kg/ha in terms of dry grain (Van der Giessen, 1949; Van Dijk, 1952). With adequate liming and fertilization, the rice yields are in the range of 4 to 5 tons/ha, though in experimental ields using hybrid rice (for example, Batang Samo and Batang Kampar) yields of 8 to 10 tons/ha have been reported (AARD, 1986; Sujitno, 2004). Grown as ladang rice, also called padi gogo or upland rice in shifting cultivation, a short-growing variety is recommended that can produce within a period of 4 months when rainfall is relatively the largest. The yields of this type of rice are usually lower, but with yields recorded at 2 to 5 tons/ha with adequate liming and fertilizer applications, they are still good rice yields, though some of the padi gogo varieties (e.g., PB-36 and Singkarak) have been reported in experimental ields to

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

yield 3 to 5 tons/ha (Sujitno, 2004). The two varieties are resistant to the blast disease, caused by the fungus Pyricularia oryzae, that often creates serious problems in the cultivation of upland rice (AARD, 1986). .... Estate crops A large variety of estate crops were grown during the prewar Dutch colonial time on the ultisols of Sumatra, including rubber, sisal (Agave sisalana), cantala (Agave angustifolia), manillahemp (Musa textilis), and many other crops that tolerate the prevailing tropical humid climate (Holthuis et al., 1950). The iber from the agave and musa crops provides important raw material for the thriving rope, cord, and string factory, located in Lampung, South Sumatra. Some tobacco cultures and a little tea were also noted in North Sumatra. Because of the need for intensive care and heavy fertilization on the nutrient-deicient ultisols, tobacco cultivation seemed later to be moved to the more fertile lowland andosols on the footslope of Mount Sibayak in North Sumatra. However, during that time, rubber was still considered the major estate crop on ultisols. But due to the threat from synthetic rubber in 1945 and hence decreasing world demand in natural rubber, much attention has been given lately to replacing it with oil palm (Elaeis guineensis), locally known as kelapa sawit. Its cultivation has since grown substantially in importance, especially with the potential for use of its crude or residual oil as biodiesel, an alternative fuel source for powering automobiles and the like (Goenadi, 2006). The country of origin of oil palm is still a big issue, though a majority of scientists believe that it was

Chapter six: Soils in the Lowlands of Indonesia

0

introduced in Indonesia from tropical Africa. However, others claim South America as the country of origin because not only E. guineensis (the only species found in Africa), but also E. Melanoccoca and many other species were found wild in South America (Van Heurn, 1950). The oil palm came in Indonesia long before the rubber “crisis,” perhaps in the nineteenth century, and like rubber is well adapted for growing in the humid tropics of Sumatra. Because the ultisols of Sumatra were reported to vary widely from rich to poor in, especially, potassium content, such conditions will be relected in the growth of the trees. A poor crop will be found on the soils low in potassium-bearing minerals (0.100% K2O soluble in 25% HCl) are noted to support better crops (Van Dijk, 1952). The average yield in 1940 was 3500 kg oil per hectare. In the wild, the oil palm grows to considerable heights, making it very dificult to harvest the fruits that develop in clusters at the tops of the trees. Recently, dwarfed trees (Figure 6.10) have been developed by proper breeding to facilitate the harvesting of the fruits by means of manually cutting the clusters from the ground with a knife perhaps attached only to a short pole. Today’s breeding programs in Indonesia are aimed at producing very short, high-yielding palms with low cholesterol and high vitamin A content. The dwarf hybrids came from the crossing between the Duras, descendants from a palm species in Bogor, and the Dumpy, a palm species from Serdang, Malaysia. At 6 to 9 years of age, the cross is reported to yield a record 30 tons per hectare

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

Figure 6.10 Dwarf oil palm tree. (Courtesy of the Indonesian Research Institute for Estate Crops. Photo provided by Dr. Ir. Didiek H. Goenadi, Director.)

annually in terms of fresh fruit bunches (FFBs) (AARD, 1986). The Indonesian Research Institute for Estate Crops considers this yield of 30 t/ha the attainable yield and believes that the genetical potential FFB yield is in the range of 35 to 40 t/ha. The oil is derived from both the mesocarp around the kernel and from the kernel itself, and the oil extraction rate (OER) is around 22%

Chapter six: Soils in the Lowlands of Indonesia

0

from the mesocarp and 6% from the kernels. Most of the vitamin A, if not all, is in the mesocarp oil (personal communication, Didiek H. Goenadi).

.

Lowland alisols

The name lowland alisols was selected to represent a group of reddish-colored soils derived from calcareous parent material, formerly known as terra rossa soils or red Mediterranean soils. These soils are called chromosols in the Australian Soil Taxonomy (Isbell, 2002), and kastanozems in the FAO-UNESCO Soil Map of the World. The closest it in the U.S. Soil Taxonomy is the alisols, though this may not agree fully with the concept of red Mediterranean or terra rossa soils, as discussed further below. Therefore, the name lowland alisols will be used in this text because of their main occurrence in the lowlands of Indonesia and in view of their close association with oxisols. Red Mediterranean or terra rossa soils, often called terra rosa or terra roxa soils, are widely spread in the Mediterranean regions, from Portugal and Spain over Italy to the Balkan peninsula. They are also found in the north coast of Africa. Of the several concepts present, the most popular is the concept as proposed by Reifenberg (1929) and Blanck (1930), who deine the soils as follows: Red Mediterranean soils are more or less deep red loams, formed on limestone as a result of speciic soil-formation processes, dictated by conditions of a typical Mediterranean climate, and generally characterized by rainy winters and hot, dry summers. The soil-forming processes may be a combination of

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

lixiviation, calciication, and laterization or ferralitization. Consequently, the soils show enrichment with sesquioxides and some silica. The high content of iron with the usually low organic matter content gives rise to the development of bright red colors, properties that distinguish them from a standard alisol of the temperate regions. Compared with other soils of the humid tropics (for example, oxisols and ultisols), they possess a higher content of alkali and alkaline earth and are also alkaline in reaction. Calcium and iron concretions may be present. Reifenberg (1929) was of the opinion that the soils should be considered as a preliminary stage of laterite formation. Such an idea was supported by Joffe (1949), who placed the soils in the group of soils affected by laterization. He also suggested that the soils might have been formed in an earlier geologic time when in the Mediterranean region a humid tropical climate prevailed. The stress upon the calcareous origin is the subject of many arguments, and many Italian soil scientists have proposed the idea of aeolian or volcanic origin (Joffe, 1949). In Indonesia, this kind of soil is found in Central and East Java, Madura, and in Nusa Tenggara, over the islands of Bali, Lombok to Timor. On the other islands of the archipelago they are of little importance.

..

Parent materials

As far as the author’s experiences are concerned, the red Mediterranean soils of Indonesia originate from reef limestone parent materials. However, a number of soil scientists in Indonesia have noticed that the

Chapter six: Soils in the Lowlands of Indonesia



soils can also be formed from calcareous sandstone and basic volcanic materials (Dudal and Supraptohardjo, 1957). They have found these soils on basaltic ash deposits, located on the lower slopes of the Baluran volcano in the eastern corner of East Java. With respect to the above, Wisaksono (1953) suggested to divide the soils into two groups: pure red limestone soils and false red limestone soils, respectively. The former has developed on pure limestone rocks, whereas the latter has been formed from calcareous materials, which have received contamination in the form of volcanic ash. The latter soils are, therefore, found more in the neighborhood of the volcanic chain. These differences in parent materials have been substantiated by results of mineralogical analyses. The pure red limestone soils possess sand fractions, composed of iron oxides and the primary minerals, zircon, tourmaline, epidote, and andalusite, considered typical minerals of old nonvolcanic sediments. On the other hand, the sand fraction of the false red limestone soil is typiied by a volcanic mineral suite, containing augite and hornblende, in addition to magnetite. The iron content in the false red limestone soil is comparatively also much higher than that of its pure counterpart. The differences in parent materials are usually coupled with the topography and the physical conditions of the soils. When formed on reef limestone or calcareous parent materials, relief is undulating. When formed on volcanic materials, relief ranges from hilly to mountainous. The pure red limestone soils are also more dificult to cultivate and behave more like heavy-textured



Soils in the Humid Tropics and Monsoon Region of Indonesia

soils than the false red limestone soil. In the dry season, pure red limestone soils tend to form wide cracks.

..

Climate

The occurrence of the soils tends to be limited to the southeastern part of Indonesia, which is generally characterized by the driest climate of the whole archipelago. As can be noticed from Table 6.13, the real (pure) terra rossa soils are located in areas with Asa or Ama (Köppen) climate types. The Asa type of climate is characterized by a long dry season from the months of May through September, where some of the months often receive less than 3 to 5 mm rainfall/ month. This dry season is alternated by a rainy season, which climaxes during the months of December, January, and February, where the highest average monthly rainfalls are recorded between 200 and 300 mm. Such a climatic pattern, common in the surroundings of Tuban, Madura, and Kupang, resembles closely that of a Mediterranean climate. However, as can be noticed from Table 6.13, the soils can also develop in Ama (Köppen) climatic types. Though this type of climate was deined earlier as a monsoon climate, the relatively longer wet season also has its climax during the period of December through February. It has a very sharp dry season with average rainfall often recorded of less than 5 mm/month.



Chapter six: Soils in the Lowlands of Indonesia

Table 6.13 The Climate of Terra Rossa Soils (Lowland Alisol) Areas in Indonesia Altitude

Location

m

Mean Annual 100 mm Rainfall Rainfall

Months

mm

Type of Climatea

Soil

Köppen S&F

East Java Terra Rossa

Tuban

0

5.6

5.2

1373

Asa

E

Bojonegoro

15

4.0

7.3

1872

Ama

C

Cepu

30

3.9

7.2

1901

Ama

C

Randublatung

55

3.1

7.7

2312

Ama

C

2006

Asa

C

Terra Rossa

Asa

E

Terra Rossa

Madura Tanah Merah

47

4.1

6.9

Nusa Tenggara Kupang a

48

6.0

6.0

1687

S&F = Schmidt and Ferguson; Köppen’s symbols: A = coldest month >18°C; a = warmest month >22°C; m = monsoon; s = summer dry season.

..

Soil morphology

The morphology of the soils is in fact not too complex. Like the other red-colored soils discussed in the preceding pages, the red Mediterranean or terra rossa soils have almost no distinct horizon differentiations. Depending on the local conditions, the soil proile may be very deep, but often it can also be thin. An example of a deep proile is given on the next page. The vegetation is composed of village garden crops with lowland fruit and kapok (Ceiba pentandra) trees and grasses as undergrowth.



Soils in the Humid Tropics and Monsoon Region of Indonesia

Horizon Depth (cm)

Description

Ap

0–33

2.5YR 3/2, dusky red, clay, weak medium crumb, friable, many roots.

B1

33–69

2.5YR 3/4, dark reddish-brown, clay, weak ine crumb to granular, friable, few CaCO3 fragments present, horizon is more compact than the A.

B3

69–95

2.5YR 3/4, dark reddish-brown, clay, weak ine crumb to granular, friable, some very faint clay coatings.

B3

95

2.5YR 3/6 dark red, clay, granular, friable, faint Fe coatings, horizon is comparatively more compact and drier.

In cases of rather thin or shallow proiles, which are more common in Madura, the dusky red surface soil is often 50 to 100 cm thick, underlain directly by the parent rock, composed of CaCO3 or calcite. Based on color differences, it appears that these red Mediterranean soils can be distinguished into the following: 1. Red Mediterranean soils with colors near 2.5YR 3/2 to 3/6. 2. Brown Mediterranean soils with colors between 7.5YR 3/2 and 6YR 3/4. 3. Red-yellow Mediterranean soil with colors near 5YR 4/4 to 6/8.

Chapter six: Soils in the Lowlands of Indonesia



This group of Mediterranean soils often occurs in association with other groups of soils according to topography. The red Mediterranean soils are located generally on top of the hills, grading into rendzinas on the slopes and into black margalitic soils (grumusols, vertisols) in the valleys where drainage conditions are the poorest. Such a sequence of soils is often found in the Rembang-Tuban hills in Central–East Java. A different topographical sequence of soils was reported by Dames (1955) in the southern mountains of Central–East Java. On top of the hills, red lateritic soils, with acid reactions, low base saturation, and exchange capacities, are grading into brown to dark brown soils on the slopes and into margalitic soils again at lower elevations or in the valleys. Soil acidity decreases, whereas base saturation, cation-exchange capacity, calcium content, plasticity, and stickiness of the soils gradually increase from the top of the mountains to the valleys as natural drainage gradually becomes poorer.

..

Soil classiication

As discussed earlier, the soils were irst called terra rossa or red Mediteranean soils and by the Australian Soil Taxonomy later identiied as chromosols (Foster et al., 2004). The FAO-UNESCO Soil Map of the World considers them to be related to kastanozems, though the description of rendzinas may also it somewhat the concept of red Mediterranean soils. In the European literature, the soils are typical for regions having a climate resembling that of a Mediterranean climate with the rainy winters



Soils in the Humid Tropics and Monsoon Region of Indonesia

and dry summers (Blanck, 1930; Reifenberg, 1929). Most European soil scientists consider the soils to be lateritic in nature, whereas some believe that they are in the initial stages of forming laterites, as indicated above. In the U.S. Soil Taxonomy, these soils are grouped in the alisols, a soil order deined as having argillic, kandic, or natric horizons, and base saturations >35% in the control zone. The soils can perhaps be placed as ustalfs, under the great group name rhodustalfs. The ustic moisture regime is correlated for tropical regions with a monsoon climate that has at least one rainy season of 3 months or more during the “winter” months. However, in the temperate regions of subhumid climates, the rainy seasons are occurring in spring and summer or in spring and fall. Such a climatic pattern, occurring, for example, in the state of Georgia, does not agree with a Mediterranean climate as described above. Nevertheless, red-colored soils, similar in morphology with oxisols or ultisols, but possessing base saturation >35% in the control zones, have been identiied in Georgia as alisols (H.F. Perkins, personal communication) and elsewhere in the southern region from the plains of the Mississippi to Texas and Oklahoma (Slusher and Lytle, 1973). Soils, identiied as Pleistocene Terra Rossas, do, in fact, exist in central Texas, which are considered more paleosols (Young, 2006). In contrast, Kubota et al. (2005) classiied terra rossas of Paraguay as either oxisols or ultisols, which seemed to have obtained tacit approval for publication from the editors of Soil Science Society of America Journal. In Indonesia, these red soils were formerly classiied as lateritic soils derived from limestone (Table 6.14), then

Chapter six: Soils in the Lowlands of Indonesia



Table 6.14 Summary of Names Used by Previous Authors for Red Mediterranean Soils in Indonesia Year Author Name 1922 1938 1944 1932 1937 1939 1950 1953 1953

1955 1957 1960 1962 1972

Mohr Mohr Mohr Te Riele Idenburg Hardon

Rood aarde (red earth) Laterite ground van kalksteen Laterite from limestone Kalk roodaarde (red limestone soil), Terra rossa Rode kalk grond (red limestone soil), Terra rossa Van der Voort Red lateritic limestone soil Wisaksono Tubuh tanah kapur merah (red limestone soil) Van Rummelen Kalk roodaarde (red limestone soil, Terra rossa; class notes, personal communication) Dames Red limestone soil, Terra rossa Dudal and Red-yellow Mediterranean Supraptohardjo soil, Terra rossa Mohr and Van Baren Terra rossa soils Dudal Red Mediterranean soils Mohr, Van Baren, and Van Schuylenborgh Red Mediterranean soils

renamed red-yellow Mediterranean soils in the 1960s by the Bogor Soil Research Institute (Dudal and Supraptohardjo, 1957; Supraptohardjo, 1961). In analogy to red-yellow podzolic soils, using the name of red-yellow Mediterranean soil then allows for subdividing the



Soils in the Humid Tropics and Monsoon Region of Indonesia

group into red, red-yellow, and brown Mediterranean soils. Today, these soils are recognized in Indonesia as alisols. Because the amounts of free sesquioxides can often reach high values in this group of soils of Indonesia, the question often arises as to why they cannot be deined as having oxic horizons too. But, the high percentages of base saturation and higher soil alkalinity may raise additional dificulties for placing them into the ustox group.

..

Physicochemical characteristics

...

Particle size distribution

The data in Table 6.15 indicate that the majority of the soils are ine in texture. They are not loamy soils as deined by Reifenberg (1929) and Blanck (1930) for a modal concept of a red Mediterranean soil, but the Indonesian varieties are more clayey soils. They also show a sharp increase in clay content from A to B horizons. Although an argillic horizon (Bt) is thus present, due to their granular and crumb structures, an excellent to good soil porosity is maintained, permitting the development of excellent internal drainage conditions.

...

Chemical characteristics

The soil reaction is in the slightly acidic category, with nearly all pH values above 6, which is in sharp contrast with the oxisols and ultisols. The same is true for the soil base saturation. This is commonly very high, often reaching values of percentage base saturation ≈99% (Table 6.15). The high base status is perhaps one of the reasons for the formation of a relatively stable crumb



Chapter six: Soils in the Lowlands of Indonesia

Table 6.15 Physiochemical Characteristics of Lowland Alisols of Indonesia Soil Profile

Particle Size Distribution (%)

pHH2O

Base Sat. %

C %

N %

C/N

>50 µ 50–2 18°C; a = warmest month >22°C; m = monsoon; w = sharp dry season.

the year. For instance, the climate of Cheribon can fall in the category of an Ama climate. However, more recently black margalitic soils have been reported by Van Loenen to be present near Lake Wissel in Papua in a perhumid region with 5000 mm annual rainfall (Mohr and Van Baren, 1960), though as stated above the soil is seldom found outside Java due to the unfavorable type of parent material for its formation. Based on topographic variations, Dames (1955) suggests dividing the soils into upland margalitic soils, as found in the Rembang-Tuban hills of Central and East Java, and lowland margalitic soils, mostly located in the plains and river valleys. It is not clear whether Dames meant to use the terms as popular terms, but the two groups of soils in question seem to differ in fertility.



Soils in the Humid Tropics and Monsoon Region of Indonesia

..

Soil morphology

The typical grumusols in Central and East Java are usually deep, dark, clayey soils, containing smectite or montmorillonitic clays. In dry conditions, the surface soil generally has a typical strong granular to ine structure, which is designated by the Dutch soil scientists as a caulilower soil structure, because of its appearance similar to a caulilower (Wisaksono, 1953). An example of a deep grumusol proile is given below: Grumusol of south Tuban (East Java). The area is characterized by a rolling topograpy and the proile is located in a valley. The vegetation is a secondary teak (Tectona grandis) forest with grass and weeds as undergrowth. Horizon Depth (cm)

Description

A1

0–17

5Y 4/1–3/1 (ield wet), dark gray to very dark gray, clay, crumb, friable, many roots.

A2

17–27

5Y 4/1, dark gray, clay, friable to slightly sticky, crumb, few small CaCO3 fragments, roots.

A3

27–45

5Y 5/1–4/1, gray to dark gray, clay, granular to weak medium blocky, friable to sticky, moderate amounts of CaCO3 fragments or concentrations, faint clay coatings, roots.

Chapter six: Soils in the Lowlands of Indonesia



AC

45–59

5Y 5/1, gray, clay, granular to ine strong blocky, friable to sticky, many CaCO3 fragments or concretions, clay coatings, ine roots.

C

59–80

5Y 4/2, olive-gray, clay, ine strong blocky, sticky, abundant CaCO3 fragments or concretions.

The solum of margalitic soils is generally considered relatively thick. Soils with very shallow topsoils, resting directly on the parent rock, are in fact not considered margalites in Indonesia, but rendzinas. This group of soils is found in the Rembang-Tuban hills, frequently occurring in an irregular pattern in association with the red Mediterranean or terra rossa soils. An example of a rendzina type of soil is given below: The soil is located in south Tuban in hilly topography. The proile is dug on a lat part of a slope in a coconut (Cocos nucifera) garden with grasses as undergrowth.

Horizon Depth (cm)

Description

A

0–14

2.5 6/2 (ield wet), light brownishgray, silt loam, crumb, friable, ine CaCO3 fragments.

D

+14

Soft limestone rock.



Soils in the Humid Tropics and Monsoon Region of Indonesia

Under the concept of grumusols, this type of rendzina belongs to the same group of margalites and other dark clayey smectite or montmorillonitic soils as deined by Oakes and Thorp (1950). As is the case in other countries, the soils in Indonesia show some variations in color and other soil properties. In the soil description above, one can notice the absence of distinct eluvial and illuvial horizons. In some cases, horizons of calcium concretions may develop to that extent that they could then qualify to be B horizons. Dames (1955) has reported that in well-developed grumusols, the particular lime horizon is sometimes 1 m thick. In other cases, interbedding of limestone plates has been observed. In the relatively more acidic soils, lime concretions are usually absent. Coarse prismatic to massive subsoil structures are common in the acidic margalitic soils, and on Sumba Island with the more extreme dry seasons, gilgai formation has been noticed (Howard, 1939). The color of the soils is often dark gray to black in the surface horizons and gray in the lower horizons. It is possible that smectite clay is not the only reason for the color, because gray colors often develop when poor drainage conditions prevail. It is then used as an indication for advanced gleization. Gleization processes have been reported to play a role in the formation of grumusols. The presence of iron concretions, frequently reported, in grumusols supports the presence of gleization. Such a case has been noted in the tirs of Morocco, and accordingly, these soils are called gley tirs (Oakes and Thorp, 1950). Dames (1955) has used the color differences for subdividing the soils of Indonesia

Chapter six: Soils in the Lowlands of Indonesia



into black margalites, dark gray to brown margalites, and yellow margalites. He believes that the humus and calcium content are partly to blame for the development of different colors. The margalitic soils rich in lime are mostly black, whereas those comparatively poor in lime are more grayish to yellow in color.

..

Soil classiication

As mentioned earlier, the soils were known in various countries under different names. In India, they were called black cotton or regur soils, whereas in Morocco names such as gley tirs, deep and crust tirs were used. According to Mohr and Van Baren (1960), the black turf soils of South Africa belonged to this category. Other names used in the past were tropical black soils and smonitza (Soil Survey Staff, 1960). In the older U.S. soil classiication system they were classiied as rendzinas. The houston clay was a typical example used by Oakes and Thorp (1950). These soils were included in the classiication system of Thorp and Smith (1949) as intrazonal soils and given the oficial name rendzina. Though Oakes and Thorp (1950) tended to agree somewhat, they also stated that the usage of the term rendzina in the United States may be in conlict with the prevailing concepts of rendzinas elsewhere in the world. They suggested the use of the term grumusol (grumus means “little heap, hillock, or crumb” in English) for all the dark clayey soils with the striking physical and structural features as previously stated. This term has since been used worldwide. With the introduction of the



Soils in the Humid Tropics and Monsoon Region of Indonesia

U.S. Seventh Approximation (Soil Survey Staff, 1960), a second attempt was made to group these soils together under vertisols (from the Latin verto, meaning “invert, to turn”), which was chiely based on the outstanding physical properties of high shrinking and swelling due to the dominating inluence of expanding 2:1 lattice types of clays. The name vertisols is maintained in the current U.S. system of soil taxonomy (Soil Survey Staff, 2006a) and also used in the FAO-UN world soil map. Why the term verti is chosen instead of verto (as is the case of andi instead of ando with respect to andisols) is still one of the many controversies of the U.S. Soil Taxonomy. The current Australian soil classiication system uses the name vertosols and sees nothing wrong with using verto, which is in fact the real Latin term for invert (CSIRO-ACLEP, 2006). In Indonesia, the soils were formerly classiied as marl soils (Dutch: mergelgrond), as indicated earlier, which was later revised by Dames (1950) into margalites. In this respect, Dames (1955) was of the opinion that margalites correlates with rendzinas. In the following years, Dudal and Supraptohardjo (1957) proposed the use of the term regur soil in the Bogor Soil Research Institute’s program of the systematic soil survey of Indonesia with the cooperation of the FAO-UN. However, this name was gradually phased out, and grumusol was at that time widely accepted in Indonesia, which was changed again recently into the name vertisols, the oficially accepted name used today in Indonesia.



Chapter six: Soils in the Lowlands of Indonesia

Table 6.17 Physicochemical Characteristics of Margalitic Soils (Vertisols) Profile Horizon

Particle Size Distribution (%)

pHH2O

>50 µ 50–2 20% Corg by weight (Driessen, 2001), and by the U.S. Soil Taxonomy deinition of histic epipedon, where the minimum limits of Corg are set at 18% or 16%, depending on the contents of the soil clay fractions (Soil Survey Staff, 2006a). The two horizons above are considered diagnostic horizons for histosols, a name chosen by USDA scientists to replace the name organic soils. From the above, it is perhaps clear that histosols are not necessarily to be peat soils, but they may include peat soils. Peat has been studied by biologists and botanists, and its science has developed the most in countries possessing huge areas of peat, such as in Russia and in Finland, where the headquarters of the International Peat Society (IPS) is also located. This society in Finland calls the areas with peat deposits peat lands, which include wetlands, moor, bog, marshes, mires, and fens. Peat lands and mires are considered wetland ecosystems, containing large accumulations of organic matter, leading to the formation of peat (IPS, 2004). The Swissbased Ramsar Convention on Wetlands, irst established in 1971 in Iran, deines peat land as a deposit of semidecayed plant material accumulated over 5000 to 8000 years (Ramsar, 2006). Other scientists are calling peat swamps and the vegetation above peat swamp forest. Some people also include mangrove swamps and tidal lowlands in this category (Driessen, 2001; Kyuma, 2003;

Chapter six: Soils in the Lowlands of Indonesia



Van den Eelaart, 2004), making the concept of peat and peat swamps very confusing. Most of the peat soils in the world are generally located in coastal plains, deltas, and luvial and lacustrine areas. According to Driessen (2001), the type of organic material may vary in the world from peat moss of the arctic and boreal regions, to sphagnum, reeds, and sedges in temperate regions, and trees of mangrove and peat swamp vegetation of the humid tropics. The sphagnum is a moss, growing in wet areas, whereas the sedges are tufted marsh plants, growing together as a bunch of luffy plants. Their remains when compacted or mixed with other plant debris form the temperate region peat. Accumulation of the decomposed material is conditioned or made possible worldwide either by low temperatures or excess water (Brady, 1990). To these, two more factors were added by Driessen (2001) for slowing the decomposition of organic residues: extreme acidity plus low nutrient content and high levels of electrolytes plus organic toxins. Other scientists consider the latter more the results rather than the reasons for peat formation, which will be explained below. Different types of peats have been recognized in the world, and different names have been used by different authors, aggravating the existing confusion about the concept of peat as mentioned earlier. The oldest, and perhaps also the simplest concept, was the division into two main types of peats: basin peat, developed in depressions or low-lying areas of marshes and bogs, and blanket peat, which forms in areas with high levels of rainfall and that practically covers the area as a blanket. Lately, low moor peats are recognized in contrast to



Soils in the Humid Tropics and Monsoon Region of Indonesia

high moor peats (Driessen, 1978, 2001). The former is usually found more in delta, marine, and luvial regions, and is considered topogenous, which is explained by Andriesse (1998) as peat affected by hydrotopography or by the action of the groundwater level. The second type, called high moor peat, is ombrogenous or peat formed by the action of rainwater only. This type of peat is found in the uplands, though Driessen added that in lowland areas the ombrogenous type could also form on top of topogenous peat. It seems, therefore, that the latter type of peat is related to basin and the ombrogenous one to blanket peat. The ombrogenous peat is called ombrophilous peat by Andriesse (1988), who considers it to be oligotrophic or a very acidic and nutrient-deicient peat. The type of water involved in the formation of this type of peat is normally low in calcium, magnesium, and potassium contents, which produces pH values of ≤4. This is in contrast to temperate region peats, called reophilous peat by Andriesse, which is more eutrophic. For example, water entering peat swamps in Scandinavia, is characterized by pH values between 6 and 7 because of enrichment with bases and nutrients leached from the surrounding lands (Moore and Bellamy, 1974). In between rheophilous and ombrophilous, Andriesse recognizes transitional peat, which he considers mesotrophic. For a more detailed discussion of the types of peat above, reference is made to Moore and Bellamy (1974) and Andriesse (1988). In Indonesia, peat soil or tanah gambut occurs extensively in the coastal lowlands, and only in Papua has some highland or mountain peat been discovered. Some believe that the peat soil is formed more inland behind

Chapter six: Soils in the Lowlands of Indonesia



the mangrove swamps, but others have reported that peat soil can exist not only in the mangrove but also in the coastal tidal swamps. The latter inds support by the existence in Indonesia of peat soils without and with pyrite. As will be explained in a later section, the pyrite as well as the tidal effect of the sea can produce very acid soils. The FAO-UN, bulletin 59, places the peat soils of Indonesia in the group of tropical peats, deined as all organic soils in the wetlands of the tropics and subtropics lying within the northern and southern latitudes of 35 degrees, including those at high altitudes (Andriesse, 1988). However, it should be realized that not all the wetlands produce peat, since in Sumatra, West Kalimantan, and Indonesian Papua, large areas of freshwater wetlands are present in addition to the peat-forming wetlands (Page, 2006). The use of the Tropical preix in the terminology of this group of peat soil is deemed essential to distinguish Tropical peat from Temperate Region Peat because of differences in formation and composition. The plant materials in the tropical regions, and in particular in Indonesia, from which the peat soils have originated are mainly trees. In temperate regions, the vegetation for peat formation, as indicated earlier, is mainly sphagnum (Sphagnum sp.) and sedges (Cyperaceae sp.). According to the Soil Map of the Soil Research Institute of Indonesia (Figure 1.2, page 16), the acreage of tanah gambut is 13,193,500 ha, next to or almost equaling the 14 million ha of the latosols or oxisols. However, the FAOUN Bulletin 59 estimated an acreage of 17 million ha of tropical peat in Indonesia, second to Canada and Russia where the extent is stated to be 150 million ha in each of



Soils in the Humid Tropics and Monsoon Region of Indonesia

the countries (Andriesse, 1988). However, such a comparison is perhaps in error, because the very large acreages in Canada and Russia are most likely composed of mixtures of temperate region peats and other soils high in organic matter. The table, as a matter of fact, uses organic soils as the title, which has, of course, a wider meaning than tropical peat soils. This group of peat soils was recognized in Indonesia only at the beginning of the twentieth century, after the discovery by Koorders in 1895 of extensive peat areas in Sumatra (Andriesse, 1988; Polak, 1950). The general consensus before that time was that peat cannot exist or be formed in the tropical climates of Indonesia, favoring rapid decomposition and mineralization of organic matter. This issue will be addressed in more detail below. Today the soils have attracted a lot of attention for use in increasing crop production due to the increasing demand for food to meet the population growth in Indonesia.

..

Parent materials

Tanah gambut or tropical peat of Indonesia originated from different kinds of materials than mineral soils (for example, oxisols, ultisols, and the like). The parent materials are vegetative remains from the vegetation of the peat swamp forest. This vegetation then equals, in essence, the meaning of a “parent rock” in terms of the genesis of mineral soil. The dead vegetative residue, deined as litter in soils science, is then the parent material for peat formation. Andriesse (1988) objects in relating litter to peat, which confuses the concept of peat and its formation even further. Litter is indeed not equal to

Chapter six: Soils in the Lowlands of Indonesia



peat, but it is the parent material for peat formation, as indicated above. The decayed litter, in various degrees of decomposition, forms the peat deposits, which depending on conditions can be 50 cm to 1 m thick. Several of the theories indicate that the peat swamp forest vegetation ordinarily develops on sediments deposited at the inland edges of coastal mangrove swamps as rivers drain toward the coast (Andriesse, 1988; Page, 2006; Wikramanayake et al., 2002). The river sediments, trapped between the tangle of mangrove roots, are slowly building up, forming a peat swamp. The latter is less subject to frequent looding and is considered by many a rain-fed swamp, which is in scientiic terms called ombrogenous. As indicated earlier, the vegetation of the peat swamp forest of Indonesia is composed of trees. At the edges of the peat swamp forest, the trees are often growing tall, with a tree trunk diameter of 50 to 80 cm at heights of 1 to 2 m. Moving to the center of the swamp, they become gradually smaller and slender, usually exhibiting narrow crowns; hence, the name of pole forest is used by Wikramanayake et al. (2002) to identify this part of the swamp forest. These trees often exhibit smaller trunks and basal areas, and because of these, the pole forest tends to have a higher density of trees. It covers the central part of the swamp forest as a dome and is believed to function as a sponge regulating water in the peat swamp. Most of the trees are not endemic, and many of the Dipterocarpaceae plants from the neighboring tropical lowland rain forest can also be found in the peat swamp forest. However, in comparison to the tropical rain forest, the variety of tree species is relatively smaller in the peat

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

swamp forest (Wikramanayake et al., 2002), whereas its composition in Sumatra and Kalimantan is reported to be not much different. Some of the major species found in both regions are the tall trees of the Shorea sp., locally called pohon meranti (pohon means “tree”), Gonystylus bancanus or locally known as pohon garu, and Tristania obavata or sumatrana or pohon mulu. The three are considered as perhaps the most valuable trees for timber. Two palm trees have also been mentioned (e.g., Livistona hasseltii and Cyrtostachys lakka) as characterizing the peat swamp forest of Indonesia by Wikramanayake and coworkers. In addition, the following trees have been reported growing in the peat regions: Plorarium alternifolium, belonging to the tea family and locally called pohon rengadean; Polyathia glauca or pohon karau; Stemonurus sp. or pohon batu item; and Radermachera gigantae or pohon tuwi batu. All four are found especially on the east coast of Sumatra. From the swamp forest of Kalimantan, the following trees have been reported, although they may also grow in Sumatra: Cratoxylon glaucum or pohon geronggang; Calophyllum sp., a fern tree, called pohon paku; Combretocarpus sp. or pohon teruntum batu; Palaquium sp. or pohon semaram; and Parastemon sp. or pohon meriawak. Destruction of the primary peat forest by natural, accidental, or deliberately set forest ires may not only be harmful to the loss of biodiversity in plant and animal life, but may also result in regrowth with gelam vegetation, trees of the paper bark Melaleuca sp., or with alang-alang grass (Imperata cylindrical). These types of vegetation, often developing as monocultures, are

Chapter six: Soils in the Lowlands of Indonesia



dificult to control, and are considered to convert the areas practically into wastelands.

...

Decomposition of litter and genesis of peat

According to Russian authorities in peat formation, the litter is generally subjected at irst to decomposition by aerobic biochemical processes of microorganisms present in the surface layers of the deposits during periods of low subsoil water (Kurbatov, 1968). The deeper layers of the peat formed by this initial process are then affected by anaerobic processes. According to Andriesse (1988), this form of peat is a forest peat, which is essentially no different from a thick litter deposit. In contrast, Andriesse believes that the tropical peat of Indonesia, mostly developing in swampy conditions, is affected more by anaerobic processes, due to speciic hydrotopographical conditions. This creates redox conditions with a substantial reduction in oxidation reactions, often relected by high sulfur and sodium contents in the peat deposits. This process of peat formation in waterlogged or reduced conditions, called by Andriesse paludiication, involves a primary peat formation at the bottom of a depression, followed by formation of a secondary peat layer on top of it, with a tertiary peat deposit above this. In the humid tropics and monsoon regions of Indonesia, with their high evapotranspiration, formation of secondary and tertiary layers of peats is considered possible only where the conditions are continuously wet, such as in the coastal lowlands of Sumatra, Kalimantan, and West Papua. Because many scientists also regard the peat ecosystem in these regions as ombrogenous or ombrophilous, the water entering the system is



Soils in the Humid Tropics and Monsoon Region of Indonesia

derived only from precipitation, as explained earlier. Andriesse (1988) believes that this type of peat is comparable to high moor peat, whereas the eutrophic low moor peat is considered more uncommon for conditions in Indonesia. Peat swamps are considered by local peat authorities as giant sponges, soaking up or adsorbing huge amounts of water from rain or rivers to release it again partly during the dry season. In this way, they serve as water catchments that are able to control loods during periods of heavy rains. They also seem to play an important role in buffering coastal lands from the harmful effect of saltwater from the sea. In addition, the peat swamps are believed to have a iltering effect, by which contaminants and potential pollutants are iltered, which may be harmful when they reach the groundwater and water of lakes and rivers of the surrounding areas.

..

Climate

In the humid tropics and monsoon regions of Indonesia, with their high temperatures and high evapotranspiration, formation of peat is possible only where the conditions are continuously wet during the year. Such conditions appear to be present in the coastal lowlands of Sumatra, Kalimantan, and West Papua. Together with the tidal effect of the sea, this combination of conditions appears to be ideal for promoting the anaerobic ecosystem needed in the accumulation of large deposits of decomposed and partly decomposed organic material, called tropical peat. The data in Table 6.19, adapted from rainfall data collected during a 30-year period

10 15

20 20

Pontianak Banjermasin

Manokwari Merauke

Afa Afa Afa Afa Afa Afa Afa Afa Afa Afa Ama

Coastal Areas of Kalimantan 0 12.0 3215 0 10.0 2411 Coastal Areas of Papua 0 12.0 3233 6.0 6.0 1402

A

A A

C A A A A A A

Tanah Gambut

Tanah Gambut

Soil

a S&F = Schmidt and Ferguson; Köppen’s symbols: A = coldest month >18°C; a = warmest month >22°C; f = humid; m = monsoon. Source: Courtesy of the Badan Meteorologi & Geoisika, Jakarta, Indonesia. (Adapted from 30 years of monthly rainfall data provided by Dadang Mishabudin, S. Kom, BMG, and Abu Dardak, former Department Chair, Agronomy, University of North Sumatra, Medan.)

30 5 5 15 10 25 30

Medan Padang Pangkal Pinang Pakanbaru Jambi Palembang Bengkulu

Coastal Areas of Sumatra 0 9.0 1947 0 12.0 4486 0 12.0 2496 0 11.0 2445 0 12.0 2161 0 11.0 2277 0 12.0 3373

The Climate of Tanah Gambut or Tropical Peat Areas in Indonesia Rainfall (months) Mean Annual Type of Climatea Altitude Location 100 mm Rainfall (mm) Köppen S&F (m)

Table 6.19

Chapter six: Soils in the Lowlands of Indonesia





Soils in the Humid Tropics and Monsoon Region of Indonesia

from 1971 to 2000 from rain stations located close to the peat swamp regions, are in support of the presence of year-long wet conditions. The only exception is perhaps the area near Merauke, Papua, where a 6-month dry period has been recorded, alternated by a 6-month wet season. The areas near Medan, Pakanbaru, and Palembang in Sumatra do not exhibit months with rainfalls >60 mm. Medan, located on the northeast coast of Sumatra, seems to be characterized by a climate with 9 rainy months of >100 mm per month. The remaining 3 months do not qualify to be called “dry” (rainfall 22°C; f = humid; i = hot summer; m = monsoon; C = warmest month >10°C and coldest month between 18°C and −3°C.

the mountains of Central and East Java. Consequently, brown forest soils with acidic reactions tend to be formed in West Java, which are called acid brown forest soils (Tan and Van Schuylenborgh, 1959; Van Schuylenborgh, 1957). On the other hand, the more traditional brown forest soils, as deined in the United States, have been developed more in the monsoonal Am climate of the mountains in Central and East Java. The issue of forming different soils due to variation in climate is

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

perhaps related to the climatic concept in Sweden of Tamm (1930), who proposed a division in climatic and aclimatic brown forest soils. The climatic types of brown forest soils are formed on parent materials poor in calcium, under a beech and oak forest. They are readily podzolized whenever the vegetation changes into a heath or coniferous forest. The aclimatic type of brown forest soil is formed on calcareous parent material or on parent material enriched with calcium from seepage water. This kind of brown forest soil is more stable and allegedly will not be inluenced by a heavy stand of a conifer forest.

..

Soil morphology

According to the original concept as proposed by Blanck (1930), the braunerde or brown forest soil is characterized by a dark-colored topsoil, rich in mull-type humus and possessing a crumb structure. Underneath the topsoil lies a brown horizon, considered the “proper” braunerde, and one or more other B-types of horizons. They may have varying degrees of rusty mottlings and varying amounts of sesquioxides or clays. The structure of the B horizons is mostly angular blocky to granular, whereas the structural units are often porous. To this description the following was recently added by the U.S. Seventh Approximation (Soil Survey Staff, 1960) and the more recent U.S. Soil Taxonomy (Soil Survey Staff, 2006a). The soils should not have a bleached (albic) E horizon and an illuvial Bt horizon. Following the deinitions above, two types of modal proiles can be recognized in Indonesia. Based on color

Chapter seven: Soils in the Uplands of Indonesia

0

differences, a light-colored and a dark-colored variety have been noticed in Indonesia. As an example, one of a lighter-colored proiles is presented below (Tan and Van Schuylenborgh, 1959): Brown Forest soil at Tawang Manggu (East–Central Java). The proile is located in an area at an elevation of 1250 m above sea level. The vegetation is a tropical rain forest. Color notation refers to air-dry and ield-wet samples, respectively. Horizon Depth (cm)

Description

0

1–0

Litter layer.

Al

0–15

10YR 5/2 to 10YR 3/2, brown to very dark gray-brown, strong medium granular, silt loam, friable, composed of predominantly earthworm cast.

A2

15–34

10YR 4/1 to 10YR 2/2, dark gray to very dark brown, strong ine crumb, silt loam, very friable, many roots.

B1

34–45

10YR 5/3 to 7.5YR 3/2, brown to dark brown, weak ine crumb, silt loam, friable, many roots.

B2

45–75

10YR 6/3 to 7.5YR 4/4, pale brown to brown, strong ine subangular blocky, silt loam, friable, few roots.

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

B3

75–114

10YR 6/6 to 10YR 5/4, brownishyellow to yellowish-brown, weak medium subangular blocky, silt loam, friable, few roots.

C

+114

10YR 7/3 to 10YR 5/3, very pale brown to brown, massive, silt loam, no roots.

As can be noticed, the color is brown throughout the proile and especially in the deeper horizons. No mechanical illuviation of clay is noticed, whereas bleaching in the subsurface horizon is absent. Due to the very dark grayish-brown (10YR 3/2) color of the topsoil, this soil is often mistaken for andosols.

..

Soil classiication

The soils were classiied in the USDA system as intrazonal soils (Thorp and Smith, 1949), but they are grouped as zonal soils in Western Europe and still are today in Eastern Europe (Karpachevsky et al., 2006). They are called brown forest soils by the Macaulay Land Use Research Institute, Kelso, England, braunerde in Germany, sol brun in France, and by other names in Hungary and Russia, such as brown earth, luvisols, planosols, arenosols, and alisols (Karpachevskiy et al., 2006). In the past, the name brown earth was often used in parts of Western Europe, whereas at one time, the soils were classiied as phaeozems and castanozems by the older FAOUN system. In the WRB, brown earths are mapped as luvisols, whereas several British and French scientists call the latter sol brun lessivé, due to the presence of a

Chapter seven: Soils in the Uplands of Indonesia

0

weakly argillic horizon. The latter is often not apparent to a casual soil surveyor. With the introduction of the U.S. Soil Taxonomy, several of the soil scientists in the United States tried earlier to place brown forest soils in the alisols and mollisols orders. But today they are recognized as inceptisols. The brown forest soils are considered in general the early stages in development of podzolic soils. This is perhaps one reason why a group of soil scientists tried to classify them as brown podzolic soils, which according to several other scientists may be related to the sol brun acides of France. Though some grouped them into the alisols, most soil scientists, however, consider them to be soils in a transitory state of formation from a young to a mature soil. Therefore, the names cambisols (from the Latin cambiare = to change) and inceptisols (from Latin inceptum = beginning) are given by the FAO, WRB, and U.S. Soil Taxonomy, respectively. Classifying brown forest soils as cambisols or inceptisols may raise a lot of arguments, because many soil scientists believe that the soils are not in the beginning phase of formation as the key terms “cambiare” and “inceptum” want to convey. Brown forest soils have well-deined A, B, and C horizons, whereas the B horizons, though lacking argillic features, are as mature as any other B horizons. In the German literature, the term podzol-braunerde has been used frequently, which was believed to be similar to a brown podzolic soil. The description presented by Altemüller (1962) for a podzol-braunerde approaches the concept of the brown podzolic soils in the United States. Krebs and Tedrow (1957) have reported the occurrence of acid brown forest soils in northern New Jersey and

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

northern New York, which at the time were oficially classiied as brown podzolic soils. The opinion that the soils are in a transformation stage of becoming brown podzolic soils remains a speculation. None of this group of soils has been noticed to convert into brown podzolic soils. The Canadian soil taxonomy used at one time the name brunisols, replacing the name brunizems, which would have placed brown forest soils as a suborder of mollisols. This has been phased out and is now no longer in use. In Indonesia, little attention is given to brown forest soils, and their classiication is therefore often neglected. In the Dutch colonial time, the soils were grouped together under the name of mountain soils. However, during the post-World War II period, the few remaining Dutch soil scientists reported that some of these mountain soils should, in fact, be classiied as brown forest soils. Van Schuylenborgh (1958) and Van Schuylenborgh and Van Rummelen (1955) described the occurrence of brown forest soils in the uplands and especially in the mountains of Indonesia. Based on soil pH and soil genetic processes, they believe that the soils can be classiied into three different kinds of brown forest soils: 1. Brown forest soils, characterized by moderately acid reactions, and formed by a combination of podzolization and calciication processes. Such soil-formation processes are possible only at higher elevations with a cooler and monsoon, Am, climate.

Chapter seven: Soils in the Uplands of Indonesia

0

2. Acid brown forest soils, characterized by strongly acidic reactions, and formed by podzolization processes. The latter occur mainly in the cooler and humid conditions of an Af climate. These are the soils that have been argued to be brown podzolic soils. 3. Latosolic brown forest soils, characterized by neutral to slightly acidic reactions, and formed by a combination of podzolization and laterization processes. These are the upland soils believed by the author to border the zones of the latosols. During the same period above, the Soil Research Institute of Indonesia began to classify all soils in the mountains as andosols, although no mention is made of andosols in their current exploratory soil map (Figure 1.2, page 16, Chapter 1). Since the Institute has adapted the U.S. Soil Taxonomy, the brown forest soils are perhaps placed today in the inceptisols order.

..

Physicochemical characteristics

...

Particle size distribution

The data in Table 7.3 indicate that brown forest soils are medium- to heavy-textured soils. The texture is mostly silt loam, and the example of silty clays is from an acid brown forest soil. The latter is located at lower elevations of West Java in regions, formerly called tension zones, deined earlier as regions where lateritic weathering and podzolization are both important processes in formation of the soils. The laterization process and resulting higher clay content are the reasons for Van

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

Table 7.3 Physicochemical Characteristics of Brown Forest Soils Profile Horizon

Particle Size Distribution (%)

pHH2O

>50 µ 50–2 40% (Agus, 2001).



Soils in the Humid Tropics and Monsoon Region of Indonesia

Albizia is at irst perhaps transplanted from its native environment in the Moluccas and Papua for use as shade trees and for several other soil conservation features in the Dutch tea, coffee, and cacao plantations in Java and Sumatra. Because it is a legume, the Dutch planters believe that as nitrogen ixers, albizia trees may enrich the soils with nitrogen to the beneit of the tea or coffee bushes. They consider the trees not to compete for this and other nutrients with the tea or coffee plants, because of their ability to develop deeper root systems. The roots are nodulated by Rhizobia and Bradhirizobia bacteria and reported to host a type of vasicular-arbuscular mycorrhizae (VAM). The rate of nitrogen ixed per year is estimated to amount to 65 to 140 kg/ha (Resh et al., 2002). Albizia trees are planted from seeds, harvested from seedpods growing on the trees. Due to the hard shell, germination of the seed is often rather dificult. However, once germinated, the plants are well known for their very rapid growth, reaching heights of 6 m (18.3 ft) and a trunk diameter of ±5 to 10 cm at the base in just 1 year. Left undisturbed, they can grow to 25 to 30 m tall and up to 1 m in diameter at the base trunk. The plants have the capacity to coppice, and sporadically, they can be harvested in 4- to 5-year cycles from the regrowth of suckers or new shoots. As indicated above, cultivation of albizia trees is conducted more on privately owned lands by small farmers and occasionally in industry-owned tree estates. Government-owned estates, on the other hand, are more interested in growing valuable high-priced hardwood trees, such as teak, whose growth is limited to the monsoon regions of the

Chapter seven: Soils in the Uplands of Indonesia



lowlands. In the local smallholder plantations, albizia is also popular as an intercrop. The albizia farms are considered by many Indonesians as well as Japanese scientists to be eco-friendly or environmentally friendly, because trees are harvested from planted farms and not cut from natural forest stands (Akihito, 2003). If this is the deinition of eco-friendly, then plantations cultivated with pine trees by the pulp and paper companies in the United States and Europe must also fall into the category of being environmental friendly. The albizia wood is white and soft and became popular because of providing cheap, affordable lumber for building huts in the villages, and all kinds of cheap furniture, boxes, and light constructions. However, the wood deteriorates rapidly and is very sensitive to infestation by termites. In Hawaii, it is used for the production of matches and matchboxes (Duke, 1983). Albizia has also attracted worldwide attention as a fuel crop. It is a renewable resource for the production of cheap charcoal, though the latter is only of low caloric value. When burned, it only provides energy to the amount of 5000 to 7000 kcal/kg. Today, the wood is also considered useful for the paper and pulp industry and has the potential of replacing pinewood as the source for pulp (Duke, 1983). The Department of Forestry in Indonesia tried recently to promote planting albizia on the east coast of Sumatra in connection with its Pamusiran project (Van den Eelaart, 2004). In an effort to integrate this project with the government reclamation programs of peat areas, reforestation of abandoned peat areas with albizia trees was suggested. A huge pulp factory was established in Jambi, capable of using a lot of raw



Soils in the Humid Tropics and Monsoon Region of Indonesia

material from albizia trees, planted in the surrounding areas of reclaimed peat lands that have deteriorated and been abandoned by the transmigration settlers. ..... Nutmeg This is one of the crops that has made Indonesia famous in the past as the Spice Islands. The nutmeg (Myristica fragans) trees, locally called pohon pala, are native of the Moluccas. Originally found by Portuguese sailors and merchants in 1511 on the Banda islands group, their cultivation later spread during the time of the Dutch East Indian Company in the 1600s to Menado, North Minehassa, Sangi, and Talaud islands, and Bengkulu, Southwest Sumatra. Many other nutmeg varieties have been reported to grow wild in other parts of the Moluccas islands. For example, the Myristica argentea is found in the Bird Head of West Papua, where it is locally known as papua-nut, the Myristica succedanea of Halmahera, called halmahera nutmeg, the Myristica speciosa of Bacan Island, south of Halmahera, locally called bacan nut, and several others. Today the crop is also grown in Mauritius, East Africa, and Grenada, in the Caribbean Islands. The crop is cultivated mainly by smallholder estates, owned by local farmers, which is conducted by planting seedlings. It is, therefore, not a true estate crop, and Indonesian authorities consider it more as an industrial crop. Though the trees will grow in the lowlands to the uplands, they grow apparently best on soils rich in humus at elevations between 400 and 700 m above sea level, where the climate is somewhat cooler but still suficiently humid through the whole year. The tree will mature and start to yield at 6 to 7 years of age, and will

Chapter seven: Soils in the Uplands of Indonesia



reach maximum production when it is 25 years old (Deinum, 1950a). With proper maintenance it may continue to give high yields for at least 50 more years. In 1930 to 1940, yields of 300 nuts (= 2 to 3 kg dry) and an additional 600 g mace per tree were considered high, though today yields of 20 to 30 times that much are called high. With the new generation of pala trees, yields of 6000 to 7000 nuts/tree/year are perhaps more common today. The plants are dioecious, requiring the cultivation of male trees for proper fruit setting by the female plants. In the past it was customary to also plant wind breakers for controlling premature fruit falls by the frequent storms occurring during the change of wet to slightly dry seasons, especially on the Banda islands. The Dutch scientists suggested the use of the tall-growing Canarium trees (Canarium commune or indicum), known locally as pohon kenari, because albizia trees, used in tea estates, provide too much shade, which should be avoided in nutmeg farms. Some shade is still necessary, which is provided by the kenari trees that can grow 40 to 50 m tall and produce, as a side beneit, edible, delicious kenari nuts. Though the hulls of the nuts are stone hard, the soft white nuts inside are consumed not only by humans but allegedly also by lemurs in the Madagascar rain forest. The pala or nutmeg fruits are oval or oblong in shape, like a small lemon. When ripe, they have a yellowish color and will split open naturally, exposing a brown nut inside, the nutmeg, covered (coated) by a red-colored aril-like membrane, called mace (Figure 7.3). The nutmeg, called locally biji pala, and the mace or fuli (in Dutch), locally known as kembang pala, are the most valuable

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

A

B

Figure 7.3 (A) Ripe nutmeg fruit at almost actual size. (B) Opened nutmeg fruit showing the seed (the nutmeg), covered by red-colored mace.

parts as spices. The meat of the fruit (pericarp) is very sour and tangy and consumed by local people in the form of candy, called manisan pala (candied nutmeg). The nutmeg farms are surprisingly less subject to attack by plant pests and diseases than are the other estate crops, perhaps due to a variety of natural chemicals contained by the plants. Nutmeg oil is known to have hallucinogenic properties and is also used even today for the treatment of toothaches and rheumatic pain. The only serious disease, known locally as the clam disease or white-split disease, is the premature splitting of fruit pods that can ruin the yield by 50% or more, because of serious damage to the nuts and mace. ..... Dairy farming This kind of operation starts to become important in the upland, due to the climate becoming favorable for dairy farming. Some dairy farms can, however, be occasionally found in

Chapter seven: Soils in the Uplands of Indonesia



the lowlands. In this case, they are located close to the proximity of large towns, where markets and consumers are available for milk and dairy products. However, the better and more productive farms are located at higher altitudes, especially in the mountains, where conditions are the most suitable for this kind of operation. Milk production is generally lowest in lowland farms, somewhat higher in upland farms, but highest in highland farms. The cows, mostly imported from the Netherlands, have been reported to yield 3098 kg of milk (per lactation and per head of cattle) on mountain farms, almost twice that produced on upland farms (AARD, 1986). More details on dairy farming will be given in the section on the soils of the mountains.

chapter eight

Soils in the mountains of Indonesia .

Introduction

The discussion in this chapter focuses on the soils located in the highlands or mountain regions of Indonesia at elevations of ≥1000 m above sea level. This region extends to an altitude of approximately 2400 m or to the summit of a volcano and includes a high-mountain region (see Chapter 3, Table 3.3). They cover a substantial part of the surface of the Indonesian archipelago. In Java alone, they are estimated to cover 21,950 km2, or 17% of the entire area of the island. The topography in the mountain regions is steep and very rough and will obviously promote erosion, whereas the cool climate may slow rapid weathering processes. The conditions are very favorable for humiication, and the high amounts of humic substances accumulating in the soils play a dominant role in soil formation. Hence, podzolization is more prominent, bringing about the characteristic pattern of mobilization of aluminum, 



Soils in the Humid Tropics and Monsoon Region of Indonesia

iron, and clays due to chelation by humic and fulvic acids. The processes are called cheluviation and chilluviation for mobilization of aluminum and iron in the form of humometal chelates. Cheluviation replaces the term eluviation, whereas chilluviation is used for the process of illuviation or the subsequent accumulation of humo-Al and humo-Fe chelates in spodic horizons. The soils also exhibit characteristic structures formed by mountain granulation, a term used by Mohr (1944), for their peculiar attributes. It differs somewhat from the granular structures of the soils in the lowlands (viz., oxisols), though some similarities with respect to the effect of iron can also be noticed. The structural units are very resistant to the impact of raindrops and have been designated as pseudosand (Mohr and Van Baren, 1960). Most probably the high content of organic matter is suspected to play an important role as cementing material in the formation of these stable structures, in addition to peptized iron substances. The interaction of organic matter in particular with paracrystalline clay and other inorganic soil materials is the big difference here from formation of soil structures exhibited by oxisols. An example of mountain granulation is shown by micropedological studies in Figure 8.1. The soil thin section also indicates the presence of a braunlehm formation, similar to that deined by Kubiena (1962) in most of these soils. The regions covered by the mountain soils have very important economic and social functions, because most of the mountain estates or plantations are located here. Tea, coffee, cinchona (quinine), and other crops are grown with success, bringing in the desired cash.

Chapter eight: Soils in the Mountains of Indonesia



Figure 8.1 Soil thin section of an A horizon of a tropical gray-brown podzolic soil at the slope of the Pangrango-Gede volcanoes complex (1100 m), showing a loose, friable, dark yellowish-brown (10YR 4/4) matrix, due to the presence of amorphous iron oxides. Large amounts of primary minerals can also be seen imbedded in the soil fabric as uncoated grains.

Despite this fact, relatively little is known about the soils, and they were formerly grouped together only under the very broad and meaningless name Mountain Soils. In addition, several of these soils were in the 1960s



Soils in the Humid Tropics and Monsoon Region of Indonesia

mistakenly recognized as andosols by Dudal and Supraptohardjo (1961). The mountain soils were known and investigated in pre-World War II time perhaps only by Senstius (1930). The investigations by Senstius were limited to a few soil proiles only, of the Lawu volcano, East Java, the Malabar volcano, West Java, and that of the Banahao mountain in Luzon, the Philippines. The soil proiles were all located at elevations of more than 2000 m above sea level, and Senstius arrived at a conclusion that the soils were affected by a type of podzolic weathering process; in other words, podzolization is involved in the formation of these soils. However, in the postWorld War II period, several Dutch scientists started reinvestigating the mountain soils in more detail, and many different soil groups were recognized. Van Schuylenborgh and Van Rummelen (1955), Tan and Van Schuylenborgh (1961a), and Tan (1965) have been able to distinguish andosols, gray-brown podzolic soils, brown podzolic soils, and podzols. The andosols were later noted to also occur in the uplands and lowlands of Indonesia. The brown podzolic soils were considered by the authors above as a transitional group, formed just above the zones of gray-brown podzolic soils and extending to the zones of podzols located at higher elevations. As discussed in Chapter 7, their existence as a distinct soil group has been questioned in some parts of the world. The soils are not well known by many scientists in Western Europe, or they are perhaps considered as a brown forest type of soil. This chapter will discuss the gray-brown podzolic soils, brown podzolic soils, and podzols, the soils affected by podzolization

Chapter eight: Soils in the Mountains of Indonesia



processes. The andosols will be addressed separately in Chapter 9 because of their different type of formation and because they may occur in the uplands as well as in the lowlands. Most of the andosols, however, are located in the mountain regions of Indonesia.

.

Highland alisols

Highland alisols were widely recognized in the past as the gray-brown podzolic soils of North America and Europe (Cline, 1949; Tavernier and Mückenhausen, 1960), but they are now called alisols for reasons described below. They are apparently important soils under deciduous and mixed forests of cool humid regions and by U.S. foresters still identiied as gray-brown podzolic soils (Stearns, 1997). The soils are rather weakly podzolized and in the United States are generally found to the south of the podzols and brown podzolic zones. They are generally characterized by distinct A, B, and C proiles, in which the A horizons show the distinct effect of cheluviation, whereas the B horizons contain more clay than either A or C horizons. These effects of cheluviation and chilluviation seem to be the outstanding characteristics of this group of soils. Based on these processes, the soils are also known as gray luvisolic or gray-brown luvisolic soil in Canada (Arocena et al., 2006) and as soil brun lessivé in the French-speaking part of Western Europe. In the U.S. Soil Taxonomy, the soils are placed in the alisols order, as indicated earlier, because of the presence of argillic-B horizons and base saturations of ≥35% in the control zones (Soil Survey Staff, 1960, 1975), features resulting from the soil-forming



Soils in the Humid Tropics and Monsoon Region of Indonesia

processes stated above. The base saturation of ≥35% was a diagnostic criterion to distinguish alisols from ultisols, until this was changed in the current U.S. versions (Soil Survey Staff, 1990, 2006a). In Indonesia, the graybrown podzolic soils are typical mountain or highland soils. To distinguish this group of zonal soils from the more lithologically lowland alisols, discussed in Chapter 6, the name highland alisols is used in the title above. A more detailed reasoning will be provided in the sections below.

..

Parent materials

In North America, gray-brown podzolic soils are derived from calcareous parent materials (Cline, 1949). However, in Indonesia they are found on intermediate volcanic materials. The mineralogical data in Table 8.1 show the parent materials to vary somewhat from andesitic to basalto-andesitic volcanic tuff. The materials from the Kendeng mountain, West Java, lack quartz and, hence, are more basic than the other two and may qualify to be called basalto-andesitic tuff with a hypersthene association. It has moderate amounts of gibbsite indicating the effect of oxidation processes in contrast to the other two materials from the Wayang and Lawu volcanoes. This relatively more intense weathering is to be expected in view of its location at lower elevations than the other two. The materials from the Wayang volcano possess small amounts of quartz and can be considered andesitic with an olivine association. Large amounts of iron concretions were detected, but no gibbsite was found in A and B horizons. The parent material from the Lawu

—

—

2

C

A

A2

tr

1

A2

B1

B2

19

26

23

27

6

13

18

20

48

47

38

35

31

Andesine Labradorite

3

3

3

3

5

7

2

tr

—

—

—

—

—

Green Hornblende

7

3

3

6

9

7

1

tr

12

14

16

14

14

Hypersthene Olivine

Volcanic Glass

Gibbsite

Iron Concretions

—

—

—

—

—

12

14

15

12

14

13

5

5

7

5

—

—

—

—

—

4

2

1

2

3

11

5

6

1

1

1

tr —

—

—

—

—

—

—

—

9

22

43

32

—

—

—

—

Lawu Volcano, East Java, 1600 m

—

3

2

1

34

19

5

8

68

25

29

23

Wayang Volcano, Pengalengan, West Java, 1620 m

–

1

1

2

1

Kendeng Mountain, Leuwiliang, West Java, 1000 m

Augite

Composition in Total Sand Fraction

21-

23

21

21

31

49

55

54

46

25

35

31

52

Rock Fragments Opaque

Mineralogical Composition of Gray-Brown Podzolic Soils

20

23

13

14

32

14

8

13

1

3

2

5

5

Green Hornblende

Sources: Van Schuylenborgh, J. and Van Rummelen, F.F.F. (1955); Van Schuylenborgh, J. (1958); Tan, K.H. and Van Schuylenborgh, J. (1960).

tr

—

A1

1

—

B2

tr

—

B1

B2

—

A2

B1

—

Quartz

A1

Horizon

Table 8.1

—

—

—

—

—

—

—

—

—

1

—

3

3

56

49

62

59

51

17

34

26

96

95

91

85

82

Hypersthene

Heavy Fraction Brown Hornblende

24

27

25

27

17

33

34

33

3

1

7

7

10

Augite

Chapter eight: Soils in the Mountains of Indonesia



0

Soils in the Humid Tropics and Monsoon Region of Indonesia

volcano is also andesitic tuff with a hypersthene-augite association. No gibbsite was detected, and the amounts of iron concretions were substantially smaller than those of the Wayang volcano.

..

Climate

Gray-brown podzolic soils are, in general, soils belonging to the cool humid regions of the United States, normally under a forest cover consisting of hemlock– northern hardwoods association. They are major forest soils and extend south to the forests of the Southern Piedmont and Blue Ridge Mountains in Georgia. In Maryland, the trees are oaks, maples, hickories, and sometimes southern white pines mixed with beeches. In Indonesia, the climatic regions of gray-brown podzolic soils vary according to local conditions. The data in Table 8.2 indicate that in West Java, characterized by a continuously humid condition (f), gray-brown podzolic soils are mainly developed in the temperate to cool mountain climates (C), but in very few exceptions the soil’s occurrence may extend to the relatively warmer Af climate types of Köppen’s system. On the other hand, in the monsoon regions (m) of Central and East Java, the soils are usually formed at higher altitudes as compared to those found in West Java. In the monsoon regions, the gray-brown podzolic soils occur more in the cool mountain Ci climates, and they have not been detected in Köppen’s Af or Am types of climates.



Chapter eight: Soils in the Mountains of Indonesia

Table 8.2 The Climate of Gray-Brown Podzolic Soils in Indonesia Altitude

Location

Mean Annual 100 mm Rainfall Rainfall

m

mm

Months

Type of Climate a

Soil

Köppen S&F

West Java (Humid) Cigombong

307

1.6

9.0

2417

Afa

B

Latosol

Podok Gedeh

900

0.4

10.1

3644

Afa

A

Podz. Latosol

Cipanas

1070

0.9

9.3

2817

Af

A

Gray Br. Podz.

Salak Volcano

2211

0.0

11.1

5467

Cfi

A

Gray Br. Podz.

East–Central Java (Monsoon) Karangpandan

307

3.7

7.6

2776

Ama

C

Latosol

Tawangmanggu

900

3.1

8.0

3194

Am

C

Brown Forest

Sarangan

1290

3.4

7.7

2533

Cfhi

C

Gray Br. Podz.

Tamansari

2480

—

—

—

Cs

—

a

S&F = Schmidt and Ferguson; Köppen’s symbols: A = coldest month >18°C; a = warmest month >22°C; f = humid; i = hot summer; m = monsoon; C = warmest month >10°C and coldest month between 18°C and −3°C; h = coldest month >0°C; s = dry summer.

..

Soil morphology

Cline (1949) deines gray-brown podzolic soils of New York as having thin A horizons overlying E horizons. In almost all cases, this E horizon can be divided into two sections: an upper part that is yellowish-brown in color and an underlying part usually pale brown or grayish-brown in color. The B horizons possess deinite higher clay contents than the A or C horizon, and are called today argillic, textural, or Bt horizons. In regions



Soils in the Humid Tropics and Monsoon Region of Indonesia

farther to the south, Cline (1949) noticed that the second E horizon is missing, very thin, or completely masked by organic matter, which is supported by Krebs and Tedrow (1957), who also reported the occurrence of gray-brown podzolic soils in New Jersey with only one brown E horizon. In Indonesia, gray-brown podzolic soils have similar morphological characteristics as indicated above. The following soil proile is presented as an example: Gray-brown podzolic soil, Lawu volcano, Central–East Java, at an elevation of 1600 m above sea level (Tan and Van Schuylenborgh, 1959). The forest vegetation is composed of Acacia decurrens, and the parent material is andesitic tuff. Drainage is noticed to be perfect. Color notations below refer to air-dry and ield-moist conditions, respectively.

Horizon Depth (cm)

Description

O

3–0

Litter, mull type.

A1

3–16

2.5Y 4/2 to 10YR 2/1, dark grayishbrown to black, strong ine subangular blocky to granular, loam, very friable, abundance of roots.

E

16–34

10YR 6/3 to 10YR 3/4, pale brown to very dark gray-brown, irregular platy, silt loam, friable, many roots.

Chapter eight: Soils in the Mountains of Indonesia



Bt1

34–50

10YR 5/4 to 7.5YR 3/2, yellowishdark brown to dark brown, weak, ine subangular blocky, loam, friable, many roots.

Bt2

50–91

10YR 6/4 to 5YR 4/4, light yellowish-brown to reddish-brown, weak, medium subangular block to crumb, silt loam, very friable, very few roots.

+91

10YR 5/8 to 6/8, brownish-yellow andesitic tuff.

C

Due to local conditions in Indonesia, variations occur from the soil proile above. The organic matter content is very high in most gray-brown podzolic soils in Indonesia, as can be noticed from the black color notation above for the A horizon. The name humic gray-brown podzolic soil is proposed for this mountain soil variety to distinguish it from that located at lower elevations. This is the soil that is also frequently confused for andosols. The A horizons of gray-brown podzolic soils located at lower altitudes are only dark brown to dark grayish-brown in color, though its organic matter content remains relatively on the high side. The E horizons are also noticed not to exhibit platy structures, whereas their colors may vary from light to dark yellowishbrown. Van Schuylenborgh (1959) suggests using the name of tropical gray-brown podzolic soil for this variety formed at lower elevations.



..

Soils in the Humid Tropics and Monsoon Region of Indonesia

Soil classiication

As previously discussed, the soils were widely recognized in the world as gray-brown podzolic soils and mapped as such in the Food and Agriculture Organization–United Nations Educational, Scientiic, and Cultural Organization (FAO-UNESCO) soils map of Western Europe (Tavernier and Mückenhausen, 1960). In French-speaking countries, the soils are additionally known under the name sol brun lessivé, whereas in the German literature the terms parabraunerde and gebleichte parabraunerde can be found (Altemüller, 1962; Manil, 1962). In Russia, the soils are recognized under quite different names. Here they are classiied as sod-podzolic soils and derno-pale podzolic soils (Tiurin et al., 1960). It is apparent from the various names above that the soils are considered in Europe as weakly podzolized soils. In the United States, the classiication of soils on the basis of soil-formation processes has unfortunately been abandoned. With the introduction of a new U.S. soil classiication system (Soil Survey Staff, 1960, 1975), soils are classiied mainly on their morphological features. Because of the presence of primarily argillic horizons and a base saturation of ≥35% in the control zone, gray-brown podzolic soils were grouped at that time together with other soils (for example, gray wooded soils and noncalcic brown soils) into one group and well into the alisols order. Gray wooded soils are the northern equivalents of gray-brown podzolic soils, a name often used in the Canadian soil classiication systems. In their more recent system, the names of gray luvisolic and gray-brown luvisolic soils have apparently replaced the

Chapter eight: Soils in the Mountains of Indonesia



name gray wooded soils (Arocena et al., 2006). In the more recent versions of the U.S. Soil Taxonomy (Soil Survey Staff, 1990, 2006a), the requirement for base saturation of alisols above has been deleted and makes one wonder whether this was a misprint or whether one has to read between the lines in using the criterion of base saturation for ultisols in this respect? For example, all other soils with argillic horizons that do not meet the requirement of a base saturation of ≥35% are not ultisols but alisols? This is very confusing for scientists in soil physics, soil microbiology, soil chemistry, and especially professionals in agricultural sciences, who are in need of soil classiication. They may not be as wellversed as a soil taxonomist and will not see this kind of reasoning in the wordy text with its many ifs, eithers, and ors. It took even the author, as a pedologist, rereading the text several times to realize the context of base saturation between ultisols and alisols above, though he is still not sure yet whether it is right or not because of the following issue. The provision of a requirement for base saturation has apparently been moved for use as a key at the kandic great group level (Soil Survey Staff, 1990, 2006a). However, the text has been changed and as it reads now, “have a CEC of 16 cmol (+) or less per kg clay,” and similarly valid for both the ultisols and alisols orders, it is in sharp contrast to the original version of a base saturation ≥35% for alisols. It will contribute to even more confusion because the kandic great groups of both the ultisols and alisols orders are identiied by an exactly similar diagnostic feature. Judging from the exploratory soil map of Indonesia (Chapter 1, Section 1.2.8), alisols are apparently



Soils in the Humid Tropics and Monsoon Region of Indonesia

unknown and hardly recognized in Indonesia. With an estimated acreage of 52,134 km2 (2.77% of the total acreage), the soils rank very low in importance. The Bogor Soil Research Institute may have included soils other than gray-brown podzolic soils in the alisols order. From the distribution on the soil map, several of the lowland soils may have been identiied as alisols, which is apparently based merely on the merits of having argillic horizons and base saturations ≥35%. The present author has also made reference in this respect to the presence of lowland alisols in Chapter 6. However, the results of the Dutch and author’s own research indicate the extensive occurrence of alisols at higher elevations, in acreages far in excess from that outlined in the soil’s map. These soils are major soils and are considered typical highland or mountain soils, affected by cheluviation and chilluviation. Therefore, gray-brown podzolic soils or alisols have been formed by distinct podzolization processes, which is contrary to the lowland alisols. Therefore, the present author suggests naming them mountain or highland alisols to differentiate them from the lowland alisols. The mountain soils can perhaps be correlated with the udalfs, with further placement preferably as tropudalfs, because they still differ in some aspects from their soils’ counterpart in the United States and other temperate regions. The use of trop (for tropics) preixes was common in the older U.S. systems of soil taxonomy, but has unfortunately been deleted in the current versions. The soils may perhaps be itted into the kandiudalf great group. However, such a placement is less likely to be correct because of the presence of relatively high pH values and of their contents of more

Chapter eight: Soils in the Mountains of Indonesia



2:1 lattice than 1:1 lattice type of clay minerals, as will be discussed below. The color of the argillic horizons is not of the required hue of 2.5YR or redder, but instead is more toward the yellower 5YR and 10YR; hence, the soils will not qualify as rhodic great groups of alisols either.

..

Physicochemical characteristics

...

Particle size distribution

The data in Table 8.3 indicate that the gray-brown podzolic soils of Indonesia are medium-textured soils. The A horizons of the tropical gray-brown podzolic as well as the humic gray-brown podzolic soils are all characterized by a silt loam texture. The clay content increases from A to B horizons, which is ascribed to mobilization of clay in the form of humo–clay complexes. The subsequent formation of argillic or Bt horizons is in conformity of prevailing concepts for placement of these soils in the alisols order.

...

Chemical characteristics

The pH values suggest the soils to be moderately acid to slightly acid in reaction. A slight tendency can be noticed that the tropical gray-brown podzolic soils, the mountain soils at lower elevations, are slightly more acidic than the humic gray-brown podzolics, the soils located at higher elevations in the mountains. The A horizon of the tropical gray-brown podzolic soil has a pH = 4.8, which places the soil in the category of strongly acid soils (pH 4 to 5) (Tan, 2005). Cline (1949) made the observations of the existence of a correlation between



Soils in the Humid Tropics and Monsoon Region of Indonesia

Table 8.3 Physicochemcial Characteristics of Gray-Brown Podzolic Soils Profile Horizon

Particle Size Distribution (%)

pHH2O

>50 µ 50–2 22°C; f = humid; m = monsoon; C = warmest month >10°C and coldest month between 18°C and −3°C; h = coldest month >0°C; i = hot summer; s = dry summer.

..

Soil morphology

Brown podzolic soils were deined by Cline (1949, 1953) to be podzols in the incipient stage. Morphologically they are, therefore, more closely related to podzols than to gray-brown podzolic soils. Generally, the proile is characterized by a layer of humus, unmixed with mineral soil, on the surface. This is underlain by a very thin A horizon and no bleached E horizon occurs. Cline

Chapter eight: Soils in the Mountains of Indonesia



(1949) indicates having observed evidence of an incipient bleicherde in the brown podzolic soils of New York. This can be noticed in the form of light gray specks or mottles in the A horizon. Such a kind of A horizon is allegedly conspicuously thick under hardwood forest. The B horizon is strong brown to yellowish-brown, and no evidence of the presence of clay accumulation is present. The brown podzolic soils of Indonesia follow a similar description. An example is provided below: Brown podzolic soil, Tapanuli, Aek Na Uli, North Sumatra, located at an elevation of 1300 m above sea level. The proile was on the lat top of a mountain. Vegetation was composed of pine trees, whereas the parent material was liparitic volcanic tuff. Color notations refer to air-dry and ield-wet conditions. Horizon Depth (cm)

Description

O

5–0

Stratiied pine needle liter.

A1

0–10

10YR 3/1 to 10YR 2/1, dark gray to black, clay loam, granular, friable, many roots.

A2

10–20

10YR 5/3 to 5YR 3/4, brown to dark reddish-brown, clay loam, granular, friable, many roots.

B

20–75

7.5YR 8/6 to 5YR 6/8, reddishyellow, clay loam, subangular blocky, friable, few roots.



Soils in the Humid Tropics and Monsoon Region of Indonesia

C1

75–90

10YR 8/3 to 10YR 6/4, pale brown to light yellowish-brown, sandy loam, granular, friable.

C2

+90

10YR 8/2 to 10YR 6/3, white to pale brown, sandy loam, granular, liparitic volcanic tuff.

The solum is thus composed of a thick A horizon, divided into a dark gray/black surface (A1) horizon and a subsurface (A2) horizon, underlain by a reddishyellow to dark yellowish-brown B horizon. Because no indication of bleaching can be detected in the A2 horizon, this horizon cannot qualify for an E (albic) horizon, usually characterizing podzol proiles. The soil texture does not differ downward in the proile. The composition of the clay fractions, however, shows evidence that podzolization is involved here, which will be discussed in more detail below.

..

Soil classiication

Most prominent soil scientists in the United States were of the opinion that the soils were weak podzols or podzols in the incipient stage. However, a great many other U.S. scientists were also skeptical about the soils being podzols, young podzols, or acid brown forest soils or whether they existed at all as a distinct group of soils. Because of such confusion, the existence of brown podzolic soils seems to have been recalled with the introduction of a new U.S. soil classiication system. In the Seventh Approximation of the Comprehensive System of Soil Classiication (Soil Survey Staff, 1960), the

Chapter eight: Soils in the Mountains of Indonesia



forerunner of the current U.S. Soil Taxonomy, brown podzolic soils were grouped together with the podzols in the spodosols order. This has remained unchanged in the newest version of the U.S. Soil Taxonomy (Soil Survey Staff, 2006b). In the German literature the name Podzol-braunerde can be found, which can be interpreted as an intergrade between a podzol and brown forest soil. It can also mean podzolized or podzolic brown forest soil, which in essence is then a brown podzolic soil. The description of this podzol-braunerde, as provided by Altemüller (1962), its the concept of a brown podzolic soil. However, in Russia, podzol-braunerde soils are considered to be dwarf-podzols (Tiurin et al., 1960). In the WRB system, the soils are called umbrisols, which is presumably based on Indonesian research indings. In Indonesia, the brown podzolic soils were discovered in 1955 by Van Schuylenborgh and Van Rummelen (1955), and since then have been recognized as a distinct zonal group of mountain soils between the zones of gray-brown podzolic soils and podzols. The Bogor Soil Research Institute has also recognized a group of soils called podzolik coklat (coklat means “brown”). The name was meant for a brown variety of red-yellow podzolic soils in the lowland (personal communication), and hence should not be confused for brown podzolic soils.

..

Physicochemical characteristics

...

Particle size distribution

The soils are all light in texture (Table 8.8). No marked clay movement can be noticed, except perhaps for a



Soils in the Humid Tropics and Monsoon Region of Indonesia

Table 8.8 Physicochemical Characteristics of Brown Podzolic Soils in Indonesia Profile Horizon

Particle Size Distribution (%)

pHH2O

>50 µ 50–2 18°C; a = warmest month >22°C; f = humid; m = monsoon; C = warmest month >10°C and coldest month between 18°C and −3°C; h = coldest month >0°C; i = hot summer; s = dry summer.

else in Indonesia have podzols been reported to occur in the lowlands. The climate in the Kubre mountain of West Papua, where the mountain podzols occur, is believed to be a Cfhi type. No weather stations are available in those remote jungle areas to conirm this. Podzols have not been found in the mountains of Java. At elevations between 400 and 900 m above sea level, red-yellow podzolic and brown forest soils are the major zonal soils in the Afa and Am climatic regions, as discussed in Chapter 7. Based on the observations above, it seems possible to distinguish in Indonesia two groups of podzols: the highland or mountain podzols and lowland podzols. The mountain podzols are zonal or climatic soils,

Chapter eight: Soils in the Mountains of Indonesia



whereas the lowland podzols can be considered as aclimatic podzols, because lithologic and topographic factors are playing a decisive role in their formation.

..

Soil morphology

The morphology of Indonesian mountain podzols does not differ much from podzols of temperate regions. An example of a soil proile description is given below: Humus-iron podzol (Tan and Van Schuylenborgh, 1961a). Proile located in Laspondom, Tapanuli, Mount Sibartong, North Sumatra, at an elevation of 1600 m above sea level. The vegetation is a primeval tropical rain forest, composed of hardwood mixed with indigenous coniferous trees. The color notations below refer to air-dry and ield-moist samples, respectively. Horizon

Depth (cm)

Description

Oe/Oa

0–20

5YR 3/4–3/3, dark reddish-brown raw humus, partly decomposed hemic and rotten sapric organic layer; when dry it can only be moistened with great dificulties.

E

20–30

5YR 5/1–4/1, gray to dark gray, weak ine crumb, sandy loam, very friable, abundance of roots; dificult to moisten.



Soils in the Humid Tropics and Monsoon Region of Indonesia

Bh

30–50

10YR 5/3–3/2, brown to very dark grayish-brown, moderately developed coarse platy, sandy loam, irm, few roots; dificult to moisten; few dark reddish-gray (5YR 4/2) mottles.

Bir or Bs

50–55

10YR 7.5/6–7.5YR 6/8, yellow to reddish-yellow, irregular platy, loam, very irm; no roots.

+55

10YR 8/1–2.5YR 7/4, white to pale yellow, massive, sandy loam, friable; yellowish-red (5YR 5/8) and yellow (10YR) 7/8) mottles; few pumice stones.

C

The A horizons in Indonesian podzols are often very thin or absent, as shown in the above proile example. This observation is substantiated by results of other investigators. Kiel and Rachmat (1948) have also described a humus iron podzol of the Dairi lands in Tapanuli, located at 1600 m above sea level, with a 30cm-thick brown spongy raw-humus layer (O horizon) lying directly on top of a light gray of the E horizon. The podzols of the Kubre mountain in West Papua are found under a shrub vegetation with scattered coniferous trees and exhibit a somewhat different morphology. According to Hardon (1936b), these soils have under an undecomposed litter layer of twigs and roots rather thick, ine sandy, irm, humic, gray to grayishbrown A horizons, overlying grayish-white E horizons. The morphological description given by Hardon indicates that the soil is perhaps an iron-podzol, because no

Chapter eight: Soils in the Mountains of Indonesia



Bh horizon is present. Mohr and Van Baren (1960) argue that soils with the above proile characteristics are perhaps not genuine podzols. However, Wilde (1957) is of the opinion that these are the typical podzols of tropical regions. The features of the Kubre mountain podzols seem to show close resemblance to the soils in New Zealand, identiied as kauri podzols, or locally also called egg-cup podzols. During the international soil science conference in New Zealand in November 1962, the present author had the chance to study kauri podzols on the spot. The soils may sometimes develop under the inluence of a single Kauri tree (Agathis australis). These trees, considered as primitive pine trees dating back from the era of the dinosaurs, are found limited to New Zealand’s northern tropical rain forest, where they are growing into huge, giant, tall trees, rivaling the sizes of the giant red oaks of California. The Kauri tree is believed to produce very acidic litter, which leads to strong local podzolization underneath the tree (Bloomield, 1954; Taylor and Pohlen, 1962), with the subsequent development of a bleached E horizon as wide as the tree crown and in the form of an egg-cup. Some of the soil scientists in New Zealand incline to relate the kauri podzol to redyellow podzolic soils. The lowland podzol of Bangka differs in morphology from the mountain podzol. It has a rather thick, loose grayish-black humus rich, quartz-sandy A horizon, overlying a bleached E layer, whereas the solum beneath is similar to that of the mountain species (Hardon, 1937). As mentioned before, the Bangka lowland podzols are intrazonal soils.

0

..

Soils in the Humid Tropics and Monsoon Region of Indonesia

Soil classiication

The classiication of these soils, though well deined in the literature, is somewhat intriguing due to a different concept in identiication developed by the USDA during the 1960s. As pointed out before, internationally the soils are distinguished by their ash-colored E horizon and hence are called podzols, derived from the Russian words pod and zola. However, in contrast to the above, the U.S. Soil Taxonomy prefers the use of the podzol-B horizon as the identifying feature, which is called spodic horizon, and the name spodosol is coined from this. In Indonesia, the name of spodosols is used. However, the soils appear to be of minor importance, because according to the Soil Research Institute (see Chapter 1, Figure 1.2, page 16), they occupy only a mere 1.16% of the total soil acreage in Indonesia. Most of the soils are generally located in remote areas high in the mountains and perhaps have escaped the attention of soil surveyors. Therefore, the author believes that more of these kinds of soils will be discovered in time when intensive soil surveys will be extended into the far corners of the mountain regions. As discussed previously, the soils can be classiied into two kinds of podzols: the highland or mountain podzols and the lowland podzols. Of these two, the mountain podzols are the most prevalent, because the lowland podzols have been discovered only on the small islands of the Bangka-Belitung group, located on the east coast of North Sumatra. Locally, these lowland podzols are called padang soil (Hardon, 1937), which some believe to be closely related to red yellow podzolic soils or ultisols. The author has

Chapter eight: Soils in the Mountains of Indonesia



not had the opportunity to investigate and conirm such a contention. Most of the lowland areas in Indonesia are already densely populated and cultivated and surveyed thoroughly, and the Soil Research Institute has not reported the occurrence of these intrazonal lowland podzols anywhere else in the lowlands area of Indonesia. The highland or mountain podzol can be distinguished into a humus-iron podzol of Sumatra and the iron-podzol of West Papua. These soils may possibly be placed in the U.S. Soil Taxonomy as Humods and Ferrods, respectively (Soil Survey Staff, 2006a, 2006b). The humods are then the spodosols that have spodic horizons enriched with humus or with humus and Aloxides. This deinition its the features of the Sumatran mountain podzols, because not iron but aluminum has accumulated in the Bhs horizon. The Fe2O3 contents of the E and Bhs horizons are 2.35% and 2.30%, respectively, as determined by the author in his soils laboratory in Indonesia. On the other hand, the Al2O3 contents of the E and Bhs horizons are 18.1 and 33.85%, respectively. The ferrods are deined as the mountain spodosols with Bs horizons only, and without comparable accumulation of humus. Such features pertain to the spodosols of the Kubre Mountains in West Papua. Perhaps the use of tropical as a preix is warranted to underline the difference in formation of Indonesian spodosols under the inluence of a tropical cool climate from that of temperate region spodosols of the northern hemisphere. It should be realized that the cool climate of the temperate region podzols includes a winter climate with ice and snow. This is in sharp contrast with the cool mountain climate of Indonesia, classiied as a



Soils in the Humid Tropics and Monsoon Region of Indonesia

Köppen’s C climate, deined as having temperatures in the coldest month of >0°C. The season is only alternated by rainy and relatively less rainy periods, whereas temperatures are usually getting lower during the wetter months. Snow and ice are only present in the Snow Mountain range (Nassau-Oranje range) of Papua, where the Idenburg top (Puncak Trikora) and the Cartensz top (Puncak Jaya) mountain summits reach 4900 and 5040 m, respectively (see Chapter 4).

..

Physicochemical characteristics

... Particle size distribution The data in Table 8.12 indicate that, as a whole, the podzols in Indonesia are coarse- to medium-textured soils. The clay contents, ranging from 1 to 15%, are very low and show a trend of eluviation from the E to accumulate in the B horizons. This is a typical feature in a podzolization process. In true podzols of the temperate regions, it is a well-established fact that clay contents decrease sharply in E horizons to increase again substantially in the B horizons. In this respect, the Bangka podzol shows this genuine characteristic for podzolization. Perhaps it can be added that in New Zealand, the clay fraction of E horizons of the kauri podzols are reported to contain large amounts of secondary silica (Taylor and Pohlen, 1962).

...

Chemical characteristics

The soils exhibit invariably very strongly acidic (pH = 4 to 3) to strongly acidic (pH = 5 to 4) reactions in especially their top soils. Soil pH values of 3 to 4 are



Chapter eight: Soils in the Mountains of Indonesia

Table 8.12 Physicochemical Characteristics of Tropical Podzols Profile Horizon

Particle Size Distribution (%)

pHH2O

>50 µ 50–2 18°C; a = warmest month >22°C; f = humid; i = hot summer; m = monsoon; s = summer dry; C = coldest month between 18°C and –3°C.

Bogor, on the slope of the Salak Volcano, at 540 to 600 m altitudes and higher. Here in the Bogor area, the soils are also present at the upper slopes of the Gedeh Volcano in the surroundings of Pasir Sarongge at approximately 1200 m or higher. North of Bandung, andosols occur on the upper slopes of the Tangkuban Prahu Volcano in the area of Lembang at 1250 m and higher. The soils are also major soils, occupying the Malabar-Pengalengan montane plateau, south of Bandung, at 1500 m and higher. The climate in the above regions ranges from the upland Afa (Köppen) to the mountain Af and Cfhi or Cf (Köppen) types of climate.

Chapter nine: Andosols of Indonesia

0

Andosols also occur in the monsoon areas of Central and East Java, where they are mostly situated in the mountains at ≥1000 m altitude. For instance, the soils exist at 2093 m altitude in the Dieng plateau, close to the areas of Wonosobo. Large areas of andosols have also been noticed in the surroundings of the Malang-Pujon highlands at 1250 m above sea level. The climate of these areas is classiied as the tropical mountain Cf and Csi types of climates. A Csi climate is a typical monsoon climate for the mountain regions in East Java (s = summer dry). It is usually characterized by a pronounced dry season from the months of May to October, but the total annual rainfall is still quite high (see Table 9.2). As mentioned earlier, Wright (1964) also reported the occurrence of andosols in South America in subhumid climates with a dry season.

.

Soil morphology

Andosols are commonly distinguished by their characteristic morphological features. In Japan, Kanno (1961, 1962) and Ohmasa (1964) reported the soils to possess thick pitch-black surface layers rich in humus; hence, the name kuroboku was assigned. This A horizon varies usually in thickness from 30 to 50 cm and is very loose, soft, and mellow. But when the soils are developed in depressions, this A horizon may often be more than 1 m thick. In this case, differentiation into two or more layers is possible. In some cases, the presence of buried A horizons, resulting from deposition of new ash layers, is also possible.

0

Soils in the Humid Tropics and Monsoon Region of Indonesia

The horizon differentiation in andosol proiles may vary from place to place. Wright (1964) noticed in South America the occurrence of andosols with AC, A(B)C, or ABC proiles, ranging from 50 cm to more than 100 cm in depth. The very dark A horizon is sharply differentiated from the yellowish-brown B or C horizons. The layer immediately below the A horizon is reported to be the most friable part of the proile, whereas the whole proile exhibits low bulk density values. Segregation of aluminum in the form of soft, waxy nodules of gibbsite was noticed by Wright (1964) in B and C horizons. One or more hardpans may also be present, but they are usually inherited depositional features, whose intrinsic properties can become reduced or accentuated by soil-forming processes. In Indonesia, andosols have similar morphological properties as discussed above. Notwithstanding the humid tropical climate, the soils still possess a black surface layer, rich in humus. An example is provided below as sampled by the author (Tan and Van Schuylenborgh, 1961a): Andosol at Glugur (Medan, North Sumatra), at an elevation of 50 m above sea level. The topography is undulating, and the vegetation is a secondary forest with Eupatorium sp. and grass as underbrush. The parent material is dacito-andesitic tuff (see Table 9.1). It is a well-drained proile. Color notations refer to air-dry and ield-moist samples, respectively.

Chapter nine: Andosols of Indonesia

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Horizon Depth (cm) Description A1 0–18 10YR 4/2-10YR2/1, dark graybrown to black, weak ine crumb, silt loam, loose, friable and soft, many ine roots. A2 18–20 10YR 4.5/2–10YR2/2, gray-brown to very dark brown, moderate ine crumb, silt loam, friable and soft, many ine roots. B 20–31 10YR 5/3–10YR3/4, brown to dark yellowish-brown, weak ine granular, loam, friable. BC 31–76 10YR7/4–10YR4/4, very pale brown to dark yellowish-brown, weak medium granular to blocky, loam slightly sticky, few small stone fragments.

The color of the A horizon may vary from black to dark brown and, consequently, one may tend to differentiate the soils into a brown and a black variety. The black variety of andosols tends to be limited more to the higher slopes of the Sibayak volcano, whereas the brown variety is associated more with the lowland areas. In Java, both varieties of andosols have also been observed, but there are no indications that the lighter-colored (brown) soils are limited to lower elevations. On the contrary, the black variety is found at Ciapus-Bogor at approximately 600 m altitude as well as in Central and East Java at elevations of ≥1000 m. The brown andosols are very speciic for the areas of Lembang and the Malabar-Pengalengan montane

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Soils in the Humid Tropics and Monsoon Region of Indonesia

plateau. In these areas, the soil has in addition a buried proile underneath. The buried soil is usually characterized by an intense black A horizon (Tan and Massey, 1964). It is possible that the black color of the buried A horizon has been accentuated after deposition of new ash layers on top, due to subsequent development of poor aeration and drainage conditions below. This may be substantiated by results of thinsection studies. Whereas usually the A horizons of mountain andosols exhibit a crumb to granular structure, similar to the structure shown in Figure 8.1, the buried A horizon seems to exhibit a relatively massive structure with little or no micropores, built up mostly by peptized black colloidal organic matter (Figure 9.1). Little inorganic material has taken part in its structural formation, and whatever aluminum and iron are present, they are probably also in peptized forms. The thin sections fail to show any changes in refraction or colors when viewed in ordinary light as well as under crossed nicols. It is believed that perhaps some kind of internal peat formation may have taken place. The soil in the surroundings of Lake Maninjau, Padang, West Sumatra, has an AC proile and a buried A horizon below. This andosol is of the brown variety and has a pronounced waxy appearance, comparable to several of the Latin American andosols, as discussed by Wright (1964). The buried A is especially extremely waxy and possesses a very high water content. When squeezed, water is lowing through the ingers. A soil proile description is given below for comparison.



Chapter nine: Andosols of Indonesia

Horizon Depth (cm)

Description

A

0–30

10YR 3/3, (ield-moist) dark brown, strong ine granular to weak crumb, silt loam, friable, waxy, ine roots.

C

30–50

10YR 5/6, yellowish-brown, weak ine granular, sandy loam, mixed with abundant ine grains of brownish-yellow (10YR 6/6) volcanic tuff.

Ab

+50

7.5YR 4/4, brown, strong ine subangular blocky to blocky, silty clay loam, friable, very waxy.

The photographs in Figure 9.2 and Figure 9.3 provide additional examples, showing black and brown andosols in Sumatra and an andosol with a buried A horizon in West Java. A thin section of this buried horizon is shown in Figure 9.1.

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Soil classiication

As stated before, a variety of names were used worldwide for this group of soils. In Japan, they were also formerly known under different names, and at one time, they were called kuroboku soils, whereas Seki (1934) was of the opinion that it seemed more reasonable to call them allitic soils because of their high aluminum contents. But the soils are affected by neither laterization nor podzolization processes (Kanno, 1961). The classiication as humic allophane soils, as proposed by Kanno (1961), appears to have received provisional acceptance only, because many scientists in Japan disagree on the basis



Soils in the Humid Tropics and Monsoon Region of Indonesia

Figure 9.1 Thin section of a buried A horizon of an andosol at the slope (1300 m altitude) of the Tangkuban-Prahu volcano, West Java. The very dark gray (10YR 3/1) dense fabric is dotted with reddish-yellow (7.5YR 6/6) iron oxides. A large plagioclase mineral is embedded near the center of the colloidal mass. (Original magniication ×100.)

that other clay minerals can be found in large amounts in addition to allophane (Egawa and Watanabe, 1964; Ohmasa, 1964). Efforts to place the importance of the type of clay mineral in the classiication of these soils have been apparent from the beginning. It is especially noted in the older New Zealand system of soil classiication. The clays in question are known in New Zealand as



Chapter nine: Andosols of Indonesia

A

B

Figure 9.2 (A) Black andosol and (B) brown andosol, Talang volcano, West Sumatra.

amorphic clays, clays that are amorphous to x-ray diffraction. Today these types of clays are called noncrystalline, paracrystalline, variable-charged clays, or short-range-order clays, depending on the preference of the authors (Tan, 2003b). It is believed that not only will these types of clays impart to the soils some of the highly distinctive physical and chemical properties, but they will also endow the soils with unusual farming properties and problems (Birrell and Fieldes, 1952; Taylor, 1964). The soils are, therefore, classiied at that time as amorphic soils (Taylor and Pohlen, 1962) and today as allophanic soils in New Zealand (Hewitt, 2003). In Latin America, a similar tendency can be noticed with regards to the importance of the clay minerals in the classiication of the soils. Wright (1964) and Besoain (1964) use the name



Soils in the Humid Tropics and Monsoon Region of Indonesia

Figure 9.3 Andosol with a buried A horizon, TangkubanPrahu volcano, West Java.

allophanic soils. In Chile and Argentina, they are locally called trumao soils, whereas in Nicaragua the soils are known as talpetate soils. The distinctive status of allophane in the classiication of this group of soils can also be noticed in the early version of the U.S. soil classiication system, called the Seventh Approximation (Soil Survey Staff, 1960). It listed as one the requirements of andepts the presence of an x-ray amorphous exchange complex or one dominated by allophane. In the new current version of the U.S. Soil Taxonomy (Soil Survey Staff, 2006), this emphasis on allophanic clays has been

Chapter nine: Andosols of Indonesia



deleted in favor of acid-oxalate extractable aluminum contents, a major requirement for the newly created diagnostic andic horizon. However, amorphous materials are still maintained today as an important feature in classiication of andosols by the Food and Agriculture Organization–United Nations Educational, Scientiic, and Cultural Organization (FAO-UNESCO) system and especially by the system of the internationally accepted WRB (FAO-UNESCO, 2007b; Shoji et al., 1996). As indicated earlier, the name andosol, selected at the 1964 FAO conference on correlation of volcanic ash soils, remains recognized today as the oficial name by the FAO and WRB systems. According to their original deinition, andosols are soils with mollic, umbric, or ochric A horizons overlying cambic B horizons and at a depth of ≥35 cm have one or both of the following: 1. Bulk densities of ≤0.85 g/cm3 (at one-third bar water retention) in the ≤2-mm soil fraction and an exchange complex dominated by amorphous materials. 2. Vitric volcanic ash, cinders, or other vitric pyroclastic materials of ≥60% in the silt, sand, and gravel fractions. Based on the properties above, the andosols are classiied into the following: I. Mollic andosols. Andosols with mollic A horizons. These soils then correlate with the black andosol variety of Indonesia.



Soils in the Humid Tropics and Monsoon Region of Indonesia

II. Humic andosols. Andosols with umbric A horizons. III. Ochric andosols. Andosols with ochric A horizons, are silt loam in texture and smeary in consistence. These can perhaps be correlated with the brown andosol varieties of Indonesia. IV. Vitric andosols. Andosols with lots of vitric volcanic ash. The above concept of classiication was later amended somewhat to underline the importance of vitric and andic as the major diagnostic criteria for andosols and to include in addition to mollic, umbric, and ochric, also histic, fulvic, melanic, and duric horizons (FAOUNESCO, 2007b). As explained earlier, in the United States, the soils were irst classiied as ando soils (Simonson, 1979; Thorp and Smith, 1949), but were later placed as a subgroup of the inceptisols (for example, andepts), with the introduction of a new system of soil classiication, known at irst as the Seventh Approximation (Soil Survey Staff, 1960, 1975). This was later amended in the newest U.S. system, called Soil Taxonomy (Soil Survey Staff, 2006), by upgrading its classiication to the orders’ level under the name of andisols. Though several Japanese scientists seem to agree in adopting the name andisols (Shoji et al., 1994), the name andosol is by far preferred. The latter is noticed in a subsequent paper by Shoji et al. (1996), where he and his American coworkers refer to andosols while trying to bring to the attention the newest WRB suggestions in subdividing the andic horizon into a vitric-andic, aluminum-andic, and silica-andic

Chapter nine: Andosols of Indonesia



horizon. They also want to underline the importance of formation of noncrystalline materials and organic matter accumulation as dominant pedogenetic processes in formation of andosols. In Indonesia, these soils were known since the early days of the Dutch colonial time. They were called in the past black dust soils by Dutch soil scientists because of the huge black dust bowls stirred up by the wind when the soils were dry (Druif, 1939a, 1939b; Mohr, 1922, 1938, 1944). In the post-World War II period, the soils were renamed andosols (Dudal and Supraptohardjo, 1961; Tan, 1964). However, at a later date after its independence, Indonesia apparently adopted the use of the name andisols, though the soils have not been listed in the oficial Soil Map of Indonesia, as stated earlier.

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Physicochemical characteristics

..

Physical properties

...

Particle size distribution

The analysis of particle size distribution is fraught with many dificulties, and even at the present, some of these have not been solved satisfactorily. According to Birrell (1964), these dificulties are caused by the presence of amorphous colloids with isoelectric points higher than those of the usual crystalline clay minerals and hydrous oxides, which induce mutual coprecipitation. In Indonesia, it was observed by Van Schuylenborgh and Van Rummelen (1955) that air drying soil samples before analysis would result in very pronounced changes in their physical conditions. Whenever possible, the soil



Soils in the Humid Tropics and Monsoon Region of Indonesia

samples are analyzed in ield-moist conditions. Drying manifests itself in the so-called mountain granulation. The soil then has a dusty appearance and is very dificult to moisten again. Because of these effects, the soil is usually easily disturbed by wind action which tends to stir up big black dust bowls; hence, the name black dust soil was given by Dutch soil scientists to the soils. In such a dry state, the soil is generally very sensitive to erosion. In the analysis for particle size distribution, peptization or dispersion of the clay fraction is not as simple in dry (oxidized) samples of andosols as compared to, for example, latosols. Samples of oxisols are usually dispersed satisfactorily with sodium pyrophosphate solutions, but this is not the case with andosol samples. It is even necessary to ind a different agent, suitable for peptizing the samples, for almost each individual horizon. Van Schuylenborgh and Van Rummelen (1955) have found that in most cases a solution of 0.005 N HCl was suficient in achieving complete peptization of andosols samples. Today dispersion or peptization can be achieved by ultrasonic means. Another problem is the fact that volcanic ash soils contain a mixture of particles which are very unstable in particle sizes. It is perhaps common knowledge that pumice, though it still has the appearance of being in its original form, will be very easily broken down into smaller particles by weak pressure or impact during particle size analysis. This is due to its weakened cohesion as a result of weathering. When weathering processes are allowed to continue further, pumice will eventually lose its own characteristic shape and form a layer of mixed colored materials, called imogo layers in



Chapter nine: Andosols of Indonesia

Table 9.3 Physicochemical Characteristics of Andosols Horizon

Particle Size Distribution (%) >50 µ 50–2