Global Commercial Potential of Subterranean Crops: Agronomy and Value Addition 3031296451, 9783031296451

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Kodoth Prabhakaran Nair

Global Commercial Potential of Subterranean Crops Agronomy and Value Addition

Global Commercial Potential of Subterranean Crops

India’s great President, late Dr. A.P.J. Abdul Kalam, launching the book Issues in National and International Agriculture, authored by Prof. Kodoth Prabhakaran Nair, in Raj Bhavan, (Office of the Governor of the State), Tamil Nadu, India

Kodoth Prabhakaran Nair

Global Commercial Potential of Subterranean Crops Agronomy and Value Addition

Kodoth Prabhakaran Nair Kozhikode, Kerala, India

ISBN 978-3-031-29645-1 ISBN 978-3-031-29646-8 (eBook) https://doi.org/10.1007/978-3-031-29646-8 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

I dedicate this book to my wife, Dr. Pankajam Nair, a nematologist trained in Europe, but one who gave up her profession when we had our son and daughter, to be a home maker. She is my all, and she sustains me in this difficult journey, that life is. Further, it is dedicated to our son, Dr. Kannan and our daughter Engineer Sreedevi and her husband Engineer Arvind. It is also my pleasure to dedicate this to Sasha, our daughter’s cocker spaniel, who is always a source of joy to us.

Preface

Among the developing countries, in particular India, which has had a great success in harnessing a lot of food production, is expected to encounter a serious food shortage, as much as 20%, in the current century. Crops like rice and wheat, the staples, have reached a yield plateau. Nearly a third of the Indian sub-continent’s geographical area, 120.40 million hectares, to be precise, a third of the total geographical area of the country at 328.53 million hectares, have now degraded soils, thanks to the highly chemical-centric farming, euphemistically known as the “green revolution”. There are thousands of hectares in Punjab State, the “cradle of Indian green revolution”, where even a blade of grass will not grow, and these lands can only be reclaimed at great cost to the nation. In fact, not just ruining the soil resources, the green revolution has contributed up to about 35% of global warming due to the emission of nitrous oxide into the stratosphere when excess urea hydrolyzes in the soil. These aspects have been elaborately discussed by Nair in his books (Nair 2018, Nair 2019). This situation is almost similar to what is happening in South Asia, after the green revolution. It is in this context that growing subterranean crops assume much critical importance and evaluation, to meet the food requirement of a burgeoning global population. And, most importantly, they can be grown in a wide range of soils, with very low fertility to very high fertility, under varying climatic and environmental conditions, such as rainfall and ambient temperature, and do not demand heavy input of chemical fertilizers, as in the case of wheat and rice. Among the 30 genera producing edible subterranean tubers and roots, cassava, sweet potato, aroids (taro, swamp taro, elephant foot yam, and tannia), yams (lesser yam, greater yam, and aerial yam) and minor crops like yam bean, country potato (coleus), and arrow root are commonly cultivated. As availability of energy will also be a limiting factor, since coal and fossil fuels get depleted, and are non-renewable, ethanol production from starch in the tuber and root crops will greatly meet the energy requirement, including biofuel to motor automobiles. Ethanol is a good example of this. Subterranean cropsbased starch is the raw material for innumerable products in bakery, confectionery, beverages, drug industry, animal, fish and bird feeds, fermentation industry, textiles industry, paper and sanitary pads and napkins production, pulp industry, and even

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warfare material need these raw materials. Hence, subterranean crops are sure bets against famine and cereal food shortages. From various projections, it is evident that by the year 2050 the world population will face a serious food shortage, if current trends in cereal consumption are taken into account. That is why subterranean crops, among the developing countries, in particular India, which has had a success in harnessing a lot of food production, is expected to encounter a serious food shortage, as much as 20%, in the current century, can meet the food requirement of the nation. Kozhikode, India

Kodoth Prabhakaran Nair

References Nair, K.P.P. (2019). Intelligent soil management for sustainable agriculture the nutrient buffer power concept. Springer Nature Switzerland AG Nair, K.P.P. (2019). Combating global warming the role of crop wild relatives for food security. Springer Nature Switzerland AG

Acknowledgements

First of all, I wish to thank Ms. Margaret Deignan, Senior Editor, Springer, who invited me to write this book. Further, I wish to place on record my sincere gratitude to Ms. Rakshana Devi Ayyanar, Project Coordinator, Springer, who so very conscientiously helped coordinate the production process initially, and Ms. Saranya Kalidoss, Project Coordinator, Springer—Total Service, who took over from Ms. Rakshana, subsequently, who has so very promptly helped stitch up the loose ends subsequently. I owe both a deep debt of gratitude. The exquisite color photos for this book were provided by Dr. M. N. Sheela, Head of the Crop Improvement Division and Acting Director, Central Tuber Crops Research Institute, Trivandrum, Kerala State, India. It is her camaraderie and generosity that has greatly enhanced the value of this important book. I owe her a very deep debt of gratitude. I would like to add a word of appreciation for Mrs. Jayanthi Narayanaswamy, Project Manager, Springer, who has been quite conscientious of her professional responsibilities on this book project, and her team for speedily incorporating all the proof corrections.

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Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2 History, Origin, and Geographical Distribution of Subterranean Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 What are the Precise Aspects of Crop Management, Post-harvest Management and Key Points of Storage of Subterranean Crops? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 A Catalogue of Field Equipment Used in the Cultivation of Subterranean Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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5 Subterranean Crops and Starches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6 The Role of Post-harvest Technology and Value Addition in Subterranean Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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7 Global Economic Potential for Value Addition in Subterranean Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 8 The Role of Bioprocessing in Protein-Enriched Animal Feed . . . . . . . 105 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

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9 Biotechnological Potential and Interventions in Subterranean Crops and Some Thoughts for Future Research in These Crops . . . . . 111 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Some Thoughts on the Future Course of Research in Subterranean Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Chapter 1

Introduction

Abstract The chapter discusses the global importance of subterranean crops in the context of food security. Subterranean crops are vast reservoirs of energy and adapt well to many adverse environmental conditions, be it soil, climatic or other, as compared to other staples like rice and wheat, and hence, there is a great need to catalogue them and their utility in the context of human food, animal feed, and industrial production of value added products. The key subterranean crops discussed are cassava, sweet potato, yam etc. Keywords Food security · Subterranean crops · Energy · Global The IFRI (International Food Policy Research Institute), Washington, USA, projects a deficit of about 41% in food production in India, by the turn of the first quarter of the current century. To meet India’s food needs of an escalating population growth, one has to look at other sources of food, besides, the main source of cereals, such as wheat and rice. It is in this context that subterranean crops assume great importance. An important feature of these crops is that they can easily adapt to marginal environments, such as soil, water requirements and climate variations. These crops are known as energy banks of nature serving as either primary or secondary staples to meet the calorific needs of a burgeoning population. Of these, sweet potato, cassava, yams etc., form an important component. Among other things, farm households see the value of subterranean crops in their ability to produce higher edible energy production per day than other crops. Yams provide 192 MJ/ha/day, sweet potato 152, while cassava 121, which is equivalent to rice (Horton & Fano, 1985).Subterranean crops have the capacity to outproduce cereals in terms of quantities of edible energy produced and harvested per unit area, per unit time. What is strikingly important is these crops produce well under conditions where other food staples like rice or wheat fail. The total trade share for subterranean crops stands at 10.5% of the international trade. The projected growth rates in output are in particular strong for potato (2.7 per cent/annum) and yam (2.9 per cent/annum). Cassava and sweet potato production will expand at a modest rate of 1.95% and 1% respectively. While these projected growth rates might appear high, they, in fact actually represent a slide in production rates. Nevertheless, future growth rates calculated for cassava, potato and yam exceed those estimated for rice and wheat (Scott et al., 2000). For both producers and © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 K. P. Nair, Global Commercial Potential of Subterranean Crops, https://doi.org/10.1007/978-3-031-29646-8_1

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1 Introduction

consumers, the versatility of subterranean crops will be a continued attraction. The chances of cassava, sweet potato and other subterranean crops being used more and more in value added products is a certainty. This book will exclusively discuss the details of the great potential in the manufacture of value-added products from subterranean crops. Expansion in non-food, non-feed uses will depend on multidisciplinary research in these crops, especially in plant breeding, biotechnology, biochemistry and socioeconomics. Through more efficient breeding techniques, and technically and economically more viable production of raw material and finished products, and strengthening growers to processor linkages, full growth potential of these crops can be achieved. Given the fundamental importance of these crops to the food economy of the world, the subterranean crops can form an important component of the global food economy. The following is crop specific discussion on the above aspects. Cassava: Nigeria leads in global cassava production followed by Brazil and The Republic of Congo. In the world India is ranked seventeenth. Within the country Kerala takes more than 80% of cassava production, followed by Tamil Nadu. In fact, cassava and sea fish (sardines, mackerel etc.,) form an essential food component of the poor Keralites. Of late, the crop is spreading to neighboring states like Maharashtra, Andhra and Karnataka etc. In the north, it has already taken roots in Assam, Meghalaya, Manipuri, Sikkim, Mizoram and Rajasthan states. However, the area under cassava in India has declined over the years; it has declined from 0.368 Mha in 1973–1974 to 0.307 Mha in 2002–2003. Also, in the principal cassava growing state Kerala, the acreage has declined from 0.13 to 0.014 Mha during the past decade. However, the production rate has remained steady. The mean productivity of cassava with supportive irrigation is 31.59 tons/ha, which is the highest production rate in the world. Sweet Potato: Inasmuch as production of sweet potato is concerned, it is The Peoples Republic of China which is at the forefront among producers. However, Israel ranks first in productivity, with a production level of 34.9 tons/ha, which is followed by Egypt at 30 tons/ha and then Japan at 25.6 tons/ha. An interesting feature of sweet potato is the number of value added products which can be made from the sweet potato tuber. These are, noodles, sorbitol, and mannitol. The Peoples republic of China lead other countries in their production. As far as India is concerned, several states of the country, such as, Orissa, West Bengal, Uttar Pradesh, Assam, Bihar, Madhya Pradesh, Jharkhand, Maharashtra, Karnataka grow the crop. Andaman and Nicobar Islands, in the neighborhood of India, popularly known as Emerald Isles with varied topography and vegetation has exceptionally high endemism and have about a total of 1000 ha sown to sweet potato. Currently, sweet potato is largely cultivated in Tamil Nadu, Kerala and Karnataka sates in India. There are a host of other subterranean crops such as aroid, yams etc. New breeds of ultra-nourishing crops which are capable of alleviating malnutrition in even the most hard-to-reach populations have been explored in tropical subterranean crops rich in

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Vitamin A and other minerals. These crops would need no commercial fortification and could be grown in small family—owned parcels of land in the interior of villages in India. The subterranean crops are also great sources of industrial raw material for the manufacture of biodiesel and starch derived materials. Corporate giants such as Toyota Group Company, Tokyo, Japan, are engaged in the manufacture of bioplastics using carbohydrates obtained from sweet potato.

References Horton, D., & Fano, H. (1985). Potato Atlas. Lima, Peru. International Potato Center (CIP). Scott, G. J., Best, R. Rosegrant, M., & Bokanga, M. (2000). Roots and tubers in the global food system. A vision statement to the year 2020. International Potato Center (CIP), 111 pp. Peru, Lima.

Chapter 2

History, Origin, and Geographical Distribution of Subterranean Crops

Abstract The chapter extensively discusses the details pertaining to origin, history and geographical distribution of key subterranean crops. Keywords Cassava · Sweet potato · Yams Example of Sweet Potato: Botanical name: Ipomoea batatas (L.) Lam Family: Convolvulaceae Edible part: Root, leaves Origin, history and geographical distribution: There are eighteen families among angiosperms, which have more than thirty genera, which produce tubers. Most genera have many species which tuberize, not within the knowledge of humankind. The precise place of origin and spread of sweet potato to other regions is still a matter of dispute. Only further precise archaeological ethnobotanical information will resolve this question. Inasmuch as available information goes, the place of origin of sweet potato is the new world, either in central America or south American lowlands. Columbus apparently discovered sweet potato in Hispaniola and Cuba during his first voyage in 1492 and on his return introduced it in Spain from where it spread to other parts of Europe. In these parts it was known as batata or padada, subsequently christened as “Spanish Potato” or sweet potato to prevent confusion with Irish potato (Solanum tuberosum L.), which reached Europe 80 years later. The subsequent spread to Europe was through two lines of transmission (1) as the batata line, from Spain and (2) the kamote line, whereby Mexican clones were imported into the Philippines by Spanish trader. Thus, the central American crop spread to other tropical parts of the world. As per FAO, sweet potato is grown in 111 countries, of which, 101 are classified as developing nations. In economic importance, sweet potato comes next only to potato.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 K. P. Nair, Global Commercial Potential of Subterranean Crops, https://doi.org/10.1007/978-3-031-29646-8_2

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Botany, Physiology and Biodiversity: Botany: Sweet potato is a herbaceous, perennial vine, cultivated as an annual. There are several hundred cultivars of sweet potatoes and great variation is found in the form and the growth habit of the plant. Some plants have trailing and twining long stems about 0.9–4.5 m long, slender, moderately thick with spaced leaves. Stems are short and with thick internodes, with purple colored leaves. Flowers are solitary. Fruit is glabrous or hirsute dehiscent capsule, 5–8 mm, which contain 2–4 angular, brownishblack seeds with a very hard testa. The root tuber are formed by thickening of pats of the adventitious roots close to the subterranean part of the stem or at the nodes which rest on the soil. Though sweet potato originated in central America the same plant was found in India, in parts of Malabar, in the state of Kerala. A number of ipomoea species have been found in the region (Van Rheedes, 2003). Physiology: Sweet potato is a plant that adapts so well to the varying environmental conditions, and, on average yields about 20 tons/ha in about five months. This, compared to cereal yield, is, huge, indeed. The underground tubers are the store banks of energy and this, in turn, depend on the photosynthetic efficiency of the leaves. Hence, tuberization and photosynthetic efficiency govern the root tuber yield (Ghosh et al., 1988). Sweet potato tuberization otato is governed by two processes, namely, tuber initiation, differentiation, and tuber development or tuber “bulking”. In the sweet potato plant certain roots exhibit lateral “swelling”, which are termed tuberous roots. The sweet potato root system is differentiated into the three following categories: 1. String roots 2. Pencil root 3. Tuber bearing roots. The above classification was made by Wilson (1982). Young roots of sweet potato turned into either tuberous root by enhanced meristematic activity of the cambium to produce starch storing parenchyma or pencil roots by more lignification of the stele cells (Togari, 1950). Research using labelled 14 C found that labelled assimilates accumulated along the vascular cambium of the storage root in 24 h following exposure of the leaves to 14 CO2 . Tuber development in sweet potato is influenced largely by the environmental impact on soil environment. Balanced partitioning following 45–60 days after planting influences bulking. Cell division and expansion and the density of starch in the cell are associated with both synthesis and accumulation of starch granules. Starch granule number and their size per cell increased from 20 to 60th day after planting and subsequently remained constant; hence increase in tuber size is associated with cell number increase.

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Sweet potato is adversely affected by waterlogging and drought. However, it tolerates drought better than flooding. When grown with accompanying crops (intercrops), the yield is reduced due to shade effect. This is due to adverse effect on flowering and the plant develops climbing habit. It has been observed in Philippines that there is a reduction of as much as 92% tuber yield when sweet potato is grown under coconut shade. Example of Cassava: Botanical name: Manihot esculenta Crantz Family: Euphorbiaceae Edible part: Root tuber A perennial shrub, which has large tuberous roots. The plant has more than 100 cultivars. It attains a height of up to 4.6 m., with large palmate leaves having 5–6 lobes. Fruit is a six-winged capsule, with seeds about 1 cm long. The plant has fibrous roots. At the plant base, some roots develop into root tubers. Two types are available: 1. Bitter type: Manihot esculenta 2. Sweet: Manihot palmate (syn.M.dulcis). Manihot genus has 98 species of which only 15 have been systematically investigated for their cytology. It has 2n = 36 chromosomes (Jos & Sreekumari, 1994). Physiology of Cassava: In terms of the calorific value/unit land and unit time, cassava produces more compared to other staple food crops. Compared to rice, which produces 110 × 103 per hectare, per day, cassava produces 176 × 103 per hectare per day, which simply proves that it is a marvelous energy supplier (Ghosh et al., 1988). For bud sprouting and establishment, cassava needs moist soil. Reserves of energy in stem cuttings provide enough energy initially for bud sprouting and establishment. After two weeks following planting, the axillary buds start to sprout. Normally two to three axillary buds elongate and produce leaves which are small with 3–5 lobes. In addition to soil moisture, ambient temperature and soil nutrient status play an important role in establishment of the crop. The critical ambient temperature for cassava establishment and optimal growth is between 18 and 20 °C. The tuber differentiation in cassava is associated with the initiation of secondary growth of root due to cambial activity. This is followed by stele enlargement which is caused by cambial activity which leads to filling with xylem parenchymatous cells, where starch granules are stored. Tuber initiation is influenced by photoperiod, ambient temperature, light intensity, and soil water availability. Roots thicker than 1 cm are classified as tuberous roots and these are noticed between 45 and 90 days after planting, which depends on the cultivars planted. Differentiation in the tuberization period noted among different cultivars may be attributed to the differences in the critical day length requirement for tuberization (Kopetz & Steinbeck, 1954).

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Table 1 Tuberization pattern due to different photoperiods

Treatments (Photoperiod duration)

Results

14–16 h

Mean tuber yields were lower, 0.1–0.2 kg/plant

10–12 h

Mean tuber yields were much higher, 0.6–0.7 kg/plant

Source Bolhius (1966)

An experiment on tuberization conducted using different cultivars showed the following results (Table 1). Optimum tuberization was found between 10 and 12 h treatment. Starch deposition: Anatomical investigations of the root for starch deposition showed that the process of tuberization in all cultivars was delayed significantly when the cassava cultivars were under shade. Such delays were extended even up to 28 days compared to the open environment and there was also significant reduction in the number of tuberous roots formed per plant under shade. Experiments conducted in East Africa (Sierra Leone) by Enyi (1973) showed that the optimum Leaf Area Index for maximum crop growth was between 4.0 and 6.5 depending on the cultivars used. However, an increase in Leaf Area Index above 3.5 leads to lessening of tuber bulking rate. There is a direct relationship between maximum photosynthetic rate and root weight and this shows that the root demand for assimilates increases photosynthetic rate. On the whole, moisture stress and salinity adversely affect cassava growth. However, cassava tolerates better salinity as compared to moisture stress. When there is extreme moisture stress, cassava plant sheds its leaves and they regrow when soil moisture increases. Intensity of leaf shedding and productivity differ among cultivars. The lateral buds of cassava remain active even under severe drought conditions, for long periods in laterite soils. This has been noticed in cassava plants growing in extreme drought conditions, where the leaf area index fell even below 0.5. Close pruning of stem during such periods induced sprouting of lateral buds forming a new canopy at the expense of storage roots. The consequent increase in canopy and higher root growth resulting in higher yield is a result of this phenomenon (Ghosh et al., 1988). The cassava plant is highly sensitive to salt injury. Cortical parenchyma decay and results in tylosis (tylose formation). A tylose is an outgrowth of a parenchyma cell through pit into a vessel element in a plant. This is also called tylosis. Cassava does best in good sunlight. It’s yield potential can only be realized when it grows under plentiful sunlight with large leaf canopy. Cyanogenic glucoside (CNG) as a secondary metabolite is accumulated in all parts of cassava, which ultimately limit the utilization of the crop as a dietary staple. There were significant positive correlations between the hydrogen cyanide content (HCN) of leaves and rind of the tuber (Moh, 1976) and flesh of the tuber (Ramanujam et al., 1984). However, different techniques

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have been perfected to reduce the CNG content of the tuber (Nambisan & Sundaresan, 1985), which involve crushing followed by sun drying, and, elimination up to 95% of the CNG has been obtained. Example of Yams: Family: Dioscoreaceae Yams belong to the genus Dioscorea, having nearly 600 species, classified under monocotyledons. The are subterranean crops. Both subterranean and aerial tubers are produced by yams. Dioecious, with male and female flowers borne by different plants, which are propagated vegetatively. Yams originate in the Indo-Burma region, which is one among the many centers of origin. The following are distributed in many regions. According to Prain and Burkill (1938), the following types are observed. 1. 2. 3. 4.

Dioscorea wallichii Dioscorea hispida Dioscorea bulbifera Dioscorea alata.

For both wild and cultivated species the chromosome numbers have been mapped. In the case of the most primitive section, Stenophora, the chromosome number is 2n = 20, although D.deltoidea the number is 2n = 40. Since yams are propagated vegetatively, some variations in the characteristic chromosome number occur in some of the cultivated forms as in D.alata (2n = 38, 2n = 52, 2n = 55, 2n = 66 and 2n = 81) (De, 1956). D.bulbifera has 2n = 36, D.cayenensis has 2n = 54 and D.dumetorum 2n = 36, 2n = 45, 2n = 55 (Meige, 1954). The Greater Yam: Dioscorea alata L.—what is it? This is a plant, in fact a climber, grows up to 15 m long with erect quadrangular winged stems twinning to the right. Opposite leaves, variable in size and shape, essentially ovate in shape, with deep basal sinus. Panicles bear the male flowers, which are often 30 cm long, and female flowers are found on small auxiliary spike. Most of the cultivars rarely produce seeds and some are completely sterile. Bulbils are sometimes found in leaf axils, and, subterranean tubers are usually single showing a great deal of variation in size, shape and color. The tuber flesh is deep reddish purple or pin in color. Bitter Yam: Dioscorea dumetorum Kunth. Bitter yam is unlike most other yams of economic value. Leaves trifoliate and tomentose, robust stems with spikes, small flowers, globose, dioecious and fertile, and the plant twines clockwise; bulbils rarely formed. Subterranean tubers are fused and medium-sized; sometimes fused together to form a cluster. Cultivated ones are non poisonous while the wild ones poisonous. Dioscorea dumetoum is very closely related to the Asian species of Dioscorea hispida, earlier explained in this chapter.

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Chinese Yam: Dioscorea opposita Thunb. The vine climbs to a height of about 3 m with round stems, more or less spineless, and tends to twine to the right. Leaves acuminate arranged in opposite directions. Leaf axils have the bulbils. Cinnamon-scented flowers, sessile in one or two receme-lime spikes sprout from the axils. Intoxicating Yam: Dioscorea hispida Dennst.—Interesting? A climber, twining to the left, unlike D.dumetorum and D.opposita which climb clockwise. Laves trifoliate, hairy. Small pale yellow flowers borne on compound inflorescences, usually large. Fruits are about 5 cm long, divided into 3 thin lobes, which are twice as much long as wide. No bulbils are produced; subterranean tubers are often lobed, sometimes elongated, and, found near the soil surface. Lesser Yam: Dioscorea esculenta Lour. Burk.—Intriguing? Growing to a height of about 2–3 m, a cylindrical-stemmed climber, twining clockwise, usually covered with spines. Small, alternate, smooth-textured leaves and no bulbils in the axils. Rare flowers in most cultivars, but, when present, they are large. Resembling sweet potatoes it produces small tubers, usually 5–20 in a plant and borne near soil surface. The following are the two distinct types, based on the supination of the roots, which are found: (1). D.fasiculata (2). D. spinosa. Potato Yam: Diosorea bulbifera L. Found throughout Africa and Asia which has spread to South and Central America, including Oceania. The plant is in a wild state. The Asiatic forms of the plant are generally superior to those of the African forms. Normally spineless cylindrical stems growing to a height of 6 m and more. Leaves usually large, simple ovate and may be alternate or opposite. Flowers are large than those in most species of Dioscorea, with spreading perianths. Small, hard, bitter tasting tubers, unpalatable in most cultivars almost absent. Edible bulbils or aerial tubers are produced in leaf axils. White Yam: Dioscorea rotundata Poir. A number of cultivars present, with large variations in form and palatability of the tubers. Cylindrical stems in some forms covered with spines, near the soil surface. Simple, usually opposite leaves, dark glossy-green in color. Vine can grow up to 12 m in favorable conditions. Cylindrical tubers, rounded and pointed at the ends. Larger specimens exist often with very distorted shapes. Yellow Yam: Dioscorea cayenensis Lam. There are many variations in form in most cultivars. Cylindrical stems covered with spines, near soil surface, the coverage degree varying greatly, are observed; opposite

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or alternate leaves, simple, pointed, leather textured and light green in color. Flowers emerge singly or in pairs; light yellow-colored tubers which vary greatly in size and form. Dioscorea abyssinica Hochst. Ethiopian native and extensively spread in the African Savannah, cultivated to a limited extent in West Africa, especially in Uganda (Burkill, 1939). Dioscorea belophylla Voigt. (syn. D.glabra var.belohylla). A species demanding scanty rain than most others, found at 4000–5000 feet high in the Himalayan region, also in Kashmir region, and Sikkim, in India. Down south of India, it is found in the Nilgiris in Tamil Nadu. Tubers are consumable, after boiling, washing and baking. These are found in rock fissures and are much relished as a very palatable tuber by the tribals living in these areas. Dioscorea glabra Roxb. A climber twining clockwise with basal prickles, smooth above; ovate, elliptic leaves, without bulbils. Buried deep in the ground the tubers are skin colored with few rootlets. The flesh is white and edible. These species occur in northern India, in the States of Assam, West Bengal, Bihar etc. Dioscorea oppositifolia Linn. Finely pubescent stemmed climber which twine in the clockwise direction; leaves opposite and alternate, with no bulbils. Single tubered, reddish in color, the species, with few rootlets, white flesh and edible. Grows widely in the Deccan plateau in north India to a height of 4000 feet (Duthie, 1973). Dioscorea pubera. This species is spread across India to Java. In Kerala, Prain and Burkill (1938) reported its existence in Trivandrum. Stem at the base upto 8 mm in diameter never prickly, but, with brownish-co green colored warts near the ground. On leafless branches main flowers can be found; female flowers as branched or simple. Tubers found deep in soil often 2 m deep, 3–8 cm in diameter. The species is also found in Car Nicobar Islands. Diosorea vexans: Rarely found, the tribals of Car Nicobar islands cultivate this species. Dioscorea deltoidea Wall. Native to the Himalayan region, in India, it is an alpine rhizomatous plant. Can grow up to an altitude of 3500 m. Rhizomes contain a toxic sapogenin, and preparations from these tuber are used to kill hair lice, and, also as a vermifuge and other medicinal purposes. Contains 2–4% diosgenin (Coursey, 1967).

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2 History, Origin, and Geographical Distribution of Subterranean Crops

Physiology: Yam tubers have a dormant period varying from two to three months after harvest and the high rate of dormancy is related to the glutathione content of the tuber. Planting freshly harvested tuber will result in delay in emergence of the plant. Storage at low temperature increased the dormancy period, while storage at high humidity reduced such dormant periods. Tuber dormancy of yam is due to the presence of polyphenolic compounds, known as, batatasins (Hashimoto et al., 1972) and abscissic acid (Hasegava & Hashimoto, 1973). A definite period of dormancy is also caused by the presence of bulbils. Investigations have been done to break dormancy through the use of chemicals. Treating tuber with 2-Chloro ethanol (Campbell et al., 1962) or by gamma radiation (Adesuyi, 1973) has brought in good results. Following the dormancy period, the yam plant goes through four distinct phases of development, as numbered below: 1. Lasts up to the sixth week of growth when root elongation and vine development takes place. The vine attains substantial growth with rudimentary leaves called “cataphylls” (Oyolu, 1982), which are absent in plants which are seed-propagated (Okezie et al., 1980). 2. Coincides with the development of primary root and shoot of the plant lasting from 6 to 10th week. 3. Coincides with rapid tuber “bulking” starting from 10th week. 4. Slow dry matter accumulation initially which peaks at 28th week and thereafter slows down until maturity of the plant. There is a direct correlation between tuber size (of yam used for planting) and ultimate plant yield which has been demonstrated by Enyi (1973). Example of Taro: Colocasia esculenta (L.) Schott Family: Araceae Taro is a cormous plant, which is perennial in nature, having big heart-shaped leaves of various size, color and shapes which sprout from underground, the plant attaining a height of about 3 m. Two to five inflorescences are found in leaf axils. Two types of Colocasia are found: 1. Colocasia antiquorum 2. Colocasia esculenta. Taro has about 1000 recognized cultivars, with the following two types 1. Eddoe 2. Taro. Both have relatively small corms surrounded by large well-developed cormels. In Colocasia esculenta var. stoloniferum, stolons are very much distinct and are the edible portion of the plant. Colocasia esculenta (L.) Schott is a single polymorphic species with several botanical and cultivated varieties. Colocasia esculenta var. stoloniferum has been

2 History, Origin, and Geographical Distribution of Subterranean Crops

13

found in parts of the Indian State, West Bengal and Assam, which produce stolons which may run some distance from the principal corm and develop into new plants at the tips. These plants are found and cultivated on swamp lands and stolons are the edible portion. Colocasia gigantea Hook. F. is native to Burma (currently named Mayanmar), which has the hydrocyanic acid, poisonous to humans and animals. Colocasia virosa occurs wild in north-eastern pats of Indi, especially, Assam and is reported to be posonus. It is a threatened species. It has been reported that there is now a new new species of Colocasia Schott, Colocasia lihengiae, restricted to the rainforest of Xishuangbanna is Southern Yunnan, in China, has been reported. There are diagnostic characteristics which distinguish the new species from the related species, Colocasia fallax Schott. Chromosome number, 2n = 28 was observed in plants of Colocasia lihengiae cultivated the Kunming Botanical Garden, in southern China (Long & Liu, 2001). Example of Tannia: Xanthosoma spp. (L.) Schott Family: Araceae Colacasia(Taro) and Xanthosoma (Tannia) are often confused with one another. The latter has appearance like taros, because, outwardly tannia looks like coarse, large taros. These grow to a height of about 2 m. Leaves are short-stemmed, large-stalked, sagittate and hastate, with sharp pointed tips, with deep wide basal lobes, and a prominent vein. Inflorescence is borne below the leaves. Corms are produced at the basal point of the plant which bear ten or more lateral cormels, normally 10–25 cm long. Xanthosoma is cultivated only to a small extent in India, especially in north India. Though there are many cultivars of tannia most edible ones are Xanthosoma sagittifolium. Somatic chromosome number is 2n = 26. The haploid chromosome complement at pachytene could be resolved into 12 types based on the morphology and staining pattern (Magoon et al., 1970). Another species of Xanthosoma, namely, Xanthosoma nigrum is with purple violet petiole, bluish pruinose young leaves and basal nerves with purple tinge whereas Xanthosoma sagittifolium is distinguished by green petiole, green young leaves and pale basal leaves. Example of Giant Taro: Alocasia macrorrhiza (L.) Schott Family: Araceae Two meters tall, succulent, herbaceous plant having large elongated stems. Leaves are arrow-shaped, pointing upwards, with a conspicuous mid rib, green in color, except the variegated forms, which can be blotched or mottled. A number Alocasia species were identified from different parts of north-east Ind. Alocasia macrorrhiza forms underground cormels. Alocasia cucullata is an ornamental small herb with lateral nerves, except the uppermost few, congested at the base in a nearly palmate arrangement. Alocasia fallax, Alocasia macrorrihiza, and Alocasia fornicata are big herbs with lateral nerves, almost equidistant, pinnately arranged. Chromosome number of most species is 2n = 28.

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2 History, Origin, and Geographical Distribution of Subterranean Crops

Example of Giant Swamp Taro: Cyrtosperma chamissonis (Schott.) Merr. Family: Araceae Rather tall, about 3 m, herbaceous with large leaves, arrow-shaped, which are about 1.5 cm long, which are borne on long petioles in a spatial arrangement, with a relatively short leaf sheath. The leaf blades have deep and sharply pointed basal lobes. Fruit is a berry and seeds of cultivated forms are frequently fertile. The corm develops by thickening at the base of the stem and almost cylindrical in shape and externally resembles a banana sucker. Cyrtosperma has 2n = 26 chromosomes (Mangenot & Mangenot, 1962). Those which have long lasting inflorescence and spectacular foliage, are the following. 1. 2. 3. 4.

Cyrtosperma cuspidispathum Cyrtosperma macrotum Cyrtosperma carii Cyrtosperma beccarianum (www.aroid.org/genera/cyrtosperma/Cyrtosprmalist. html).

Elephant foot Yam: Amorphophallus spp. Family: Araceae Rather tall, with about 9 m thick stem, bearing at top a single tripartite leaf, each part of which is divided into numerous segments. The life span of the is rather, about 4–6 years, and towards its end a large terminal inflorescence blooms, consisting of a short stalk and spathe and spadix, which emits a malodorous smell, reminiscent of rotten meat. The corms are large globose, depressed tubers, usually dull yellow or brownish-yellow in color, and these produce 5–10 corms or cormels, at the end of each growing season. The Western Ghats of Kerala State, India, is home for many wild species, such as, the following, were found. 1. Amorphophallus dubius, A.wigtii 2. A.sylvaticus.Kunth. Example of Hausa Potato: Solenostemon rotundifolius (Poir.), J.K. Morton syn. Plectranthus rotundifolius (Poir.) Spreng (Coleus parviflorus) Family: Labiatae A short-statured plant, either climbing or prostrate, with thick leaves and a succulent stem. There are pale violet colored flowers on an elongated receme, and, small dark brown colored tubers are produced. It has 2n = 64 or 2n = 84 number of chromosomes. Coleus, also known as Chinese potato is botanically known as Solenostemon rotundifolius (Poir) is cultivated, on a small scale, in southern India. It is native to West Indies.

2 History, Origin, and Geographical Distribution of Subterranean Crops

15

Example of Arrowroot: Maranta arundinacea L. Family: Marantaceae A fairly tall (about 2 m) plant, herbaceous dichotomously branched perennial, with large, fleshy, cylindrical underground rhizomes. The plant has lanceolate leaves, with white flowers arranged in twin clusters, which very rarely produce red seeds. The plant is popularly known as West Indian arrowroot. The tubers have much medicinal values and is a staple for infants and invalids. The following two cultivars ae recognized: 1. St. Vincent, “Creole”, which has long thin rhizomes. 2. “Banana”, which has shorter, thicker less fibrous rhizomes produced near soil surface. The second cultivar is more easily adapted to mechanical harvesting; it’s chromosome number is 2n = 18 (Sato, 1960), 2n = 48 (Simmonds, 1954). The genus has about 25 species. The leaves fold upwards, hence, the common name, arrowroot. Example of East Indian Arrowroot: Tacca leontopetaloides (L.) Kuntzae Family: Taccaceae Tacca genus has thirty species all with tuberous creeping rhizomes, about 90 cm tall, with broad, deeply lobed, divided single leaves. Tubers are starchy. Inflorescence is borne on a long, rather slender peduncle. Single leaf is erect, and long stalked. The fruit is about 0.5 cm long, ovoid, smooth, six-ribbed with persistent perianth. Two types are seen (1) one which produces large number of potato-sized tubers and (2) produces a single large tuber. The plant produces numerous seeds, pale brown in color and ribbed. It has 2n = 30 chromosomes for Tacca (Baldwin & Spece, 1951). Example of Safed Musli: Family: Liliaceae The plant grew naturally in dense forests and is a traditional Indian medicinal plant. It is sub-erect, has lanceolate leaves, and a tuberous root system. Grows up to 45 cm in height. Tubers grow into the soil to a depth of about 30 inches. It can grow up to an altitude of 1500 m above mean sea level. It originates from the Indian sub-continent, an annual herb with tubers, crown, leaf and flower as useful parts. The plant has a chromosome number of 2n = 4x = 28. Example of Gloria superba: Family: Liliaceae/Calchicaceae The plant is a herbaceous, semi-woody branching climber, which can easily grow up to 5 m tall. From a single fleshy V-shaped cylindrical tuber 1–4 stems arise, which are edible. Leaves are stalkless, alternate or opposite, lance-shaped, in whorls of up to 3, 5–15 cm long and 4–5 cm wide, with parallel veins and tips ending in a spiral tendril which are used to climb. Plants cannot tolerate water stagnation, loves sunlight, and can thrive in low fertility soils. It can grow up to a height of 2500 m above mean sea

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2 History, Origin, and Geographical Distribution of Subterranean Crops

level. Grows luxuriously in cool temperature, native of tropical Asia and Africa. It is commonly known as “Glory Lily” or “Malabar Lily”. The chromosome number varies from 2n = 22 to 2n = 80/90 (Sharma & Sharma, 1961). Example of Indian Bread Root: Psoralea esculenta Family: Fabaceae The plant is a herbaceous one, native to prairies and dry woodland, of USA and Canada. And it bears a starchy tuberous root edible as a root vegetable. It is concurrently called “Indian Potato”, “Pomme Blanche” (white apple) and “Teepsenee. From where the plant is, in the soil or in the field, several densely—haired stems emerge, growing to a length of up to 30 cm, bearing palmately compound leaves divided into five leaflets. In summer, plenty of blue or purple-colored flower are produced, in terminal clusters of 5–10 cm long, leading to flattened, slender-tipped pods. The plant emerges from one or more sturdy roots, brown colored, forming rounded tuberous bodies about 10 cm below soil surface, each 4–10 cm long. These are edible, as raw, dried or cooked in water, or other media. They taste like turnip. Dried root can be ground to flour and edible bread/chapathis (North Indian bread) can be made out of the ground floor. For Native Americans and early European explorers, these very palatable tuber formed the staple food. The plant’s remarkable characteristics qualify it for possible domestication.

References Adesuyi, S. A. (1973). Advances in yam storage research in Nigeria. In 3rd International Symposium on Tropical Root crops (13 pp.). IITA Ibadan, Nigeria. Baldwin, J. T., & Spece, B. M. (1951). Tacca involucrata its chromosomes. Bulletin of the Torrey Botanical Club, 78(1), 70–72. Bolhius, G. G. (1966). Influence of length of illumination period on root formation in cassava. Netherlands Journal of Agricultural Science, 14, 251–254. Campbell, J. S., Chukueke, V. O., Teriba, F. A., & Ho-A-Shu, H. V. S. (1962). Some physiological experiments with the white Lisbon yam (Dioscorea alata L.). 1. The breakage of the rest period in tubers by chemical means. Empire Journal of Experimental Agriculture, 30, 108–114. Coursey, D. G. (1967). Yams (p. 230). Longan. Duthie, J. F. (1973). Flora of the Upper Genetic Plain. Vol, II-III Part I-II. M/s. Bishan Singh Mahendra Pal Singh, Dehradun. M/s. Periodical Experts. Delhi, pp. 255. Enyi, B.A.C. (1973). Growth, development and yields of some tropical root crops. In Proceedings of 3rd Symposium International Society for Tropical Root Crops (pp. 87–103). Ibadan, Nigeria. Ghosh, S. P., Ramanujam, T., Jos, J. S., Moorthy, S. N., & Nair, R. G. (1988). Tuber Crops. Oxford IBH Publishing Company Private Ltd. Hashimoto, T., Hasegava, K., & Kawarada, A. (1972). Batatasins: New dormancy inducing substances of yam bulbils. Planta, 108, 369–374. Hasegava, K., & Hashimoto, T. (1973). Quantitative changes in batata sins and absicissic acid in relation to the development of dormancy in yam bulbils. Plant Cell and Physiology, 14, 369–377. Jos, J. S., & Sreekumari, M. T. (1994). Genetic Resources in cassava. In K. L. Chadha & G. G. Nayar (Eds.) Advances in Horticulture, Vol. 8. – Tuber Crops (pp. 17–33). Malhotra Publishing House.

References

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Kopetz, L. M., & Steineck, O. (1954). Photoperiodische Untersuchungen an Karotofelsamlingen. Zucher, 24, 69–77. Long, C.-L., & Liu, K.-M. (2001). Colocasia lihengiae (Araceae: Colocasieae), a new species from Yunnan. China Botanical Bulletin of Academia Sinica, 42, 313–317. Mangenot, S., & Mangenot, G. (1962). Enquete surles nambre chromosomiques dam une collection d’especes tropicales. Revue Cytologie et Biologie Vegetale, 25(3–4), 411–447. Magoon, M. L., Krishna, R., & Vijaya Bai, K. (1970). Cytological studies in Xanthosoma sagittifolium. Nucleus, 13, 142–148. Meige, J. (1954). Nombres chromosomiques et repartition geographique de quelques plants tropicales et equatorials. Revue Cytologie et Biologie Vegetale, 15(4), 312–348. Moh, C. C. (1976). Correlation between hydrocyanic acid level in leaf and root of cassava (Manihot esculenta Crantz.). Turrialba, 26, 132–133. Nambisan, B., & Sundaresan, S. (1985). Effect of processing on the cyanoglucoside content of cassava. Journal of the Science of Food and Agriculture, 36, 1197–1203. Okezie, C. E., Okankwo, S. N. C., & Noveke, F. I. (1980). Genetic pattern and growth analysis of the white guinea yam raised from seed. In E. R. Terry, K. A. Odure, & F. Caveness (Eds.) Trop. Root Crops. Research Strategies for the 1980s (pp. 180–188). IDRC-163e. Oyolu, C. (1982). Inherent constraints to high productivity and the production cost in yam (Dioscorea spp.) with special reference to Dioscorea rotundata Poir. In J. Miege & S. N. Lyonga (Eds.) Yams (pp. 147–160). Clarendon Press. Prain, D., & Burkill, I. H. (1938). An account of the genus Dioscorea in the East. Part III. Annals of the Royal Botanic Garden, Calcutta, 14, 211–528. Ramanujam, T., Indira, P., & Rajendran, P. G. (1984). Distribution of HCN in cassava and its relationship with anthocyanin pigments. South Indian Horticulture, 32, 132–137. Sato, D. (1960). The karyotype analysis in Zingiberales with special reference to the prokaryotype and stable karyotype. Scientific Papers, Cell Genetics Education University of Tokyo, Department of Biology, 10(2), 225–243. Simmonds, N. W. (1954). Chromosome behaviour of some tropical plants. Heredity, 8(1), 139–145. Togari, Y. (1950). A study on the tuberous root formation of sweet potato. Bulletin of National Agricultural Experiment Station Tokyo, Japan, 68, 1–96. Van Rheede (2003). Hortus Malabaricus (Reprinted Eng. Ed.). Vol II, 2003. University of Kerala. 245pp. Wilson, L. A. (1982). Tuberization in sweet potato (Ipomoea batatas (L.) Lam). In: R. S. Villareal & T. D. Griggs (Eds.) Sweet Potato (pp. 79–84). Taiwan: AVRDC.

Chapter 3

What are the Precise Aspects of Crop Management, Post-harvest Management and Key Points of Storage of Subterranean Crops?

Abstract The chapter discusses, at length, the various details of crop management of the several key subterranean crops, with special emphasis on fertilizer use economy, post-harvest technology, storage etc. Keywords Sweet potato · Cassava · Taro · Yams · Post-harvest · Storage · Sweet potato weevil (spw) Sweet Potato: The tuber yield and quality of sweet potato are influenced much by the right kind of nutrition and water management. These cops need the macro, secondary and micro nutrients in optimum quantities to tap their yield potential to the maximum. The details of crop management of each of the crops is discussed below: Soil and Climatic Requirements: Well-drained, fertile, sandy loam soils are best suited for sweet potato. potato cultivation. Ideally, the optimum soil pH must be in the range of 5.2–6.7, in the neutral range. Excessive alkalinity, salinity and waterlogging are very harmful to sweet potato, adversely affecting much the tuber development. Inasmuch as climatic requirements are concerned, sweet potato does best when the ambient temperature is between 20 and 27 °C. For proper tuberization, the ideal temperature range is 20–25 °C. Regions with an average ambient temperature of 24 °C and annual rainfall of 750 or more are most suitable for sweet potato cultivation. No tuber development takes place when the ambient temperature is more than 40 °C, and temperature below 10 °C damages the plants. Short day with low light intensity promote root development, while excess of rainfall and long days promote the vegetative growth, reducing tuber yield. How to propagate and what planting material is required?: Cuttings of vine, obtained from seed nursery or from harvested plants are the propagule. Vine cuttings from seed nursery are preferable for good yield while those obtained from harvested mature crop are used when two crops are taken.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 K. P. Nair, Global Commercial Potential of Subterranean Crops, https://doi.org/10.1007/978-3-031-29646-8_3

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3 What are the Precise Aspects of Crop Management, Post-harvest …

How to prepare Seed Nursery?: The seed nursery preparation has a two-step procedure as detailed below: 1. Mode of preparing the primary nursery: Around two months before planting the vines in the main field, primary seed nursery is prepared. Normally 100 m2 of area is used and 100 kg of mediumsized, weevil free seed tubers, weighing 125–150 g each, are enough for planting one hectare of land. The tubers are planted 25 cm apart on ridges formed at a spacing of 60 cm. Fifteen days after planting urea is applied @ 1.5 kg urea/100 m2 to ensure quick growth of vines and the nursery may be irrigated alternate days during the first 10 days after planting and thrice a week thereafter. The Clipping vines to about 30 cm after 45 days after planting, for replanting purposes, in the secondary nursery, is recommended. 2. Mode of preparing the secondary nursery: In the secondary nursery, the vines obtained through the primary nursery preparation and subsequently planting, are now multiplied. The secondary nursery has an area of 500 m2 , which can produce enough planting material to plant one hectare of land. Half a ton of farm yard manure (FYM), exclusive cattle manure or compost may be applied at the beginning of the preparation of the secondary nursery. Vines obtained from the primary nursery are planted at a spacing of 20 cm on ridges formed 60 cm apart. Urea @ 1 kg/100 m2 may be applied in two split doses on the 15th and 30th day after initial planting. For planting main fields, the vines are ready after 45 days from the date of planting. How to select planting material?: Vines about a feet long, having three to four nodes are found to be the most ideal as planting material. The cuttings obtained from the apical and middle portion of the vines are preferred, to obtain higher sprouting percentage, consequently, higher tuber yield. Vine Preparation: Vine cuttings with intact leaves are stored under shade for two days before planting in the main field to promote better root initiation, early establishment and consequently higher yield. When to plant?: In India, sweet potato is grown during the main south-west monsoon period, mainly as a rainfed crop (Kharif season, June to August), also as an irrigated crop (Rabi season, October–December). But, most sweet potato is grown in India during the autumn, when days are warm and sunny and nights are cool, coupled with moderate rainfall. In north India, both in Bihar and Uttar Pradesh states, the crop is also planted during February-March months as a spring crop, which is invariably irrigated.

3 What are the Precise Aspects of Crop Management, Post-harvest … Table 1 Fertilizer schedule

State where grown

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N (kg/ha) P (kg/ha) K (kg/ha)

Bihar, West Bengal, Assam 40

40

60

Andhra Pradesh

60

60

60

Karnataka

60

90

60

Kerala

75

50

75

What is the methodology used for planting? Four different planting methods are followed a follows: 1. 2. 3. 4.

Ridge and Furrow Mound Bed Flat.

Ridge and Furrow planting gives higher tuber yield and is very convenient for inter cultural operations. Land is ploughed to a depth of 10–20 cm to obtain a fine soil tilth. Vines are planted, spaced 20 cm apart on the ridges of 20 cm height, made 60 cm apart. Only the middle of the vines with the nodes is buried at a depth of 5–10 cm, keeping both ends exposed. Vertical planting on the ridge for sweet potato, highly saline soil is recommended for the State of Uttar Pradesh, flat planting is preferred for Bihar State and for Andhra Pradesh and North-East India ridge method of planting is recommended. What seed rate to use and what spacing to provide?: Between rows it must be 60 cm and between cuttings 20 cm which will entail a total to 8300 cuttings/ha. Depending on the region where the crop is grown, spacing will be decided. In Indo Gangetic Plains of India, 30 × 30 cm, between rows and between cuttings is recommended. In Bihar State, 345 × 4 cm is recommended. Based on soil conditions and soil moisture regime, closer planting acco-modates higher plant density leading to higher tuber yield. What should be the fertilizer schedule? The details are given in Table 1. At the time planting time, full dose of phosphorus fertilizer as well as potassic fertilizer and half dose of nitrogen fertilizer is applied. The remaining half dose of nitrogen fertilizer is applied a month later at the time of first weeding and earthing up. Application of the recommended dose of nitrogen fertilizer along with Azospirillum (a nitrogen fixing bacterium) vine dipping at 2 kg/ha and soil application of 10 kg/ha was recommended for the states of Tamil Nadu and Kerala in south India and Assam, Bihar and West Bengal in north India. In the case of micronutrient deficiencies, Zinc sulfate (1–2%), Ammonium ferric sulfate (1–2%) and manganese sulfate (0.1%) spray are recommended. How best to irrigate the crop?: For proper establishment of the crop, a light irrigation is given, immediately after planting. Sweet potato is extremely susceptible to water stress/water logging, and,

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3 What are the Precise Aspects of Crop Management, Post-harvest …

Table 2 A summary of ideal cropping systems for sweet potato State of India

Recommended cropping system

Northern India: North Bihar

(1): Kharif maize–autumn sweet potato–rabi wheat and summer green gram (2): Kharif maize-sweet potato-onion in summer rainy season (March–April)

West Bengal

(1): Green gram (summer)–Colacasia (pre-Kharif) sweet potato (autumn) (2): Green gram–elephant foot yam–sweet potato

Orissa

(1): Mid-season paddy (rainfed)–sweet potato–fallow (2): Maize-sweet potato-fallow

Kerala (low land) (1): Paddy (summer)–paddy (winter)–sweet potato (2): Paddy–sweet potato–fallow Tamil Nadu

Sweet potato–cereals

Andhra Pradesh

Maize–sweet potato–vegetables

Madhya Pradesh

Vegetable (cowpea)–sweet potato

Uttar Pradesh

Vegetable (cowpea)–sweet potato

Chattisgarh

Vegetable (cowpea)–sweet potato

Maharashtra

Vegetable (cowpea)–sweet potato

it should be strictly ensured that irrigation is provided at the critical stage of crop growth, which is 40 days after planting. A moisture stress at this stage will invariably lead to substantial loss in tuber yield. What is the role of weeding and earthing up?: For optimum crop growth, ensure that the crop is not subjected to weed growth through weed competition. The intercultural operation, like earthing up, should be carried out 30 days after planting, which ensures good soil conditions, free of weeds. This may be followed by a second earthing when the crop is 50 days old, which will ensure the crop is free of weeds and good soil tilth which will enable good tuber formation, leading to good final yield. The role of training and pruning in sweet potato cultivation: Sweet potato plant grows rapidly initially after a good establishment. In order to check excessive vegetative growth, the plant must be lifted at internodes 30 days after planting so that rooting is prevented and tuber formation followed by tuber swelling is facilitated. Which are the cropping systems in sweet potato?: The sweet potato plant has been observed to grow under various cropping systems in the eastern and southern regions of India. Table 2 summarizes some of the ide cropping systems. What is the role of intercropping in sweet potato cultivation?:

3 What are the Precise Aspects of Crop Management, Post-harvest …

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In cashew gardens, up to the pre-bearing stage (5 years) it is common practice to plant sweet potato as an intercrop. A fertilizer dose of 60 kg N + 40 kg of phosphorus + 60 kg of potassium/ha) is recommended and it is a popular practice in the Konkan region of Maharashtra state. When to harvest and what are the post-harvest operations in sweet potato cultivation?: Sweet potato crop matures in about four and a half months after planting and is ready for harvest. Normally, harvesting after four months is recommended, a delay causes weevil attack. A light irrigation is provided prior to harvest to enable easy digging out of the tubers. A normal crop can be harvested after 120 days since planting. While early maturing cultivars can be harvested in 90–105 days, medium maturing ones can be harvested in 4 months. What is the yield potential of sweet potato crop?: Fluctuates between 10 and 20 metric tons per hectare, based on the variety grown and how good/optimum the method of cultivation, fertilizer schedule etc., are. Yields up to 30 tons/ha can be achieved by optimum conditions of cultivation. Marketing: Sweet potato tubers are highly susceptible to sweet potato weevil attack; it is recommended that fresh tubers are marketed immediately after harvest. How best to store?: When stored for a long period, after harvest, under improper storage conditions like poor ventilation, moisture seepage into storage space etc., the tubers get shrunk. Immediately after harvest, the tubers must be spread properly under shade for about a week. Subsequently they are properly healed and cured which can then be stored in well-ventilated rooms. Good ventilation in the storage space is a must in the case of sweet potato storage. Cassava: What are the optimum soil and climatic requirements for cassava?: Susceptible to water logging, cassava requires, a well-drained loamy soil with a pH range of between slightly acidic to neutral. The cassava plant tolerates drought better than does sweet potato. More than half of Asia’s cassava cultivation is confined to the ultisols; In southern India, it is in both ultisols and alfisols in Kerala State, and vertisols in Tamil Nadu. It can grow in regions from humid (where the annual rainfall is > 200 cm) to semi-arid regions where t is between 50 and 70 cm. Cassava can be grown up to an altitude of 2000 m above mean sea level, but, performs better at lower altitudes where the temperature rang is between 25 and 32 °C. Unlike sweet potato, it is a drought tolerant crop, which cannot withstand frost because its growth ceases below 10 °C. Cassava is commonly cultivated as an annual crop between latitudes 30° North and South, at altitudes above 2000 m above mean sea level, in equatorial regions,

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with an annual precipitation ranging from 50 to 800 cm. Tolerates hot climate, but, below 20 °C plant growth is not normal, and storage root yield decreases drastically. Crop duration fluctuates between seven months to one year, and, in cooler climate growth is slowed down resulting in lower starch accumulation. In such a climate the crop grows for two to three years although the palatability of the crop, when cooked, diminishes with ageing of tubers due to higher fiber content (Ravi & Mohankumar, 2004). How is cassava propagated and what planting material to sue?: The crfop is vegetatively through stem cuttings, called “setts”. Only for breeding purposes is true cassava seed used. When freshly harvested, cassava seeds germinate quite rapidly when the ambient temperature vries from 25 to 35t °C. Previously collected stems are generally used for raising a new crop. One year old cuttings, free of pests (insects and diseases) chosen, about 10 cm thick. After discarding the top one third of the stem, the portion from middle and bottom when planted gives better tooting and soil establishment. A smooth circular cut, rather than an irregular cut. Gives uniform callusing and root initiation. It is economical to use setts of 25–30 cm length. When to plant cassava?: When irrigated, the crop can be planted throughout the year. When rainfed, the best planting time is April–May or August–September. What planting methods to use? For cassava?: Different planting methods used, one “vertical” (perpendicular to the ground), slanted (45° to the ground), and horizontal are common. Uniform callusing results around the cut surface, from “vertical” planting, facilitating uniform distribution of tuber formation, roots all round the base of the plant. Shallow planting facilitates production of higher root number, but, a planting depth of 5 cm is optimum. How to space and obtain optimum plant density in cassava? The branching type of the cassava sett, whether branching or non-branching, decides the plant density in the field. Branching and semi-branching types require 90 cm × 90 cm (between setts and between sett rows), while non-branching types require 75 cm × 75 cm spacing, for optimum yield. The optimum plant population at these spacings ranged from 12,000 to 17,000 setts/ha. Normally, one sett is planted per hill; though planting two setts will lead to higher yield, the tuber size will be consequently reduced. What is the optimum fertilizer schedule for cassava?: Both organic and inorganic fertilizers are applied. As organic source, plain cattle manure, farm yard manure (FYM) @ 10 tons/ha is used. One kg of FYM is put into the pits where the sett is planted and covered up with top soil. Additionally, N:P:K at the rate of 100–50–100 kg ha−1 respectively is applied for long duration cassava varieties and N:P:K at the rate of 75:50:75 kg ha−1 is applied for short duration

3 What are the Precise Aspects of Crop Management, Post-harvest …

25

varieties. Green manuring with fast growing vegetable cowpea varieties (B-61 or C-152) can be used as substitutes for FYM. The following schedule is recommended for fertilizer application: 1. At planting time: Full dose of phosphate fertilizer plus half dose of nitrogen and potassic fertilizer 2. 45–60 days after planting: Remaining half dose of nitrogen and potassic fertilizers. This should coincide with the first weeding and earthing up operations. In the states of Gujarat, Kerala and Maharashtra the N:P:K ratio is maintained at 100:50:100 kg/ha, respectively However, the fertilizer application schedule is similar to the above practice. Use of bio fertilizers has been found very effective for cassava in acidic soils, which not only enhance tuber yield, but also, reduce the quantity of chemical fertilizers used. In Andhra Pradesh and Tamil Nadu, the following application schedule is practiced: Half dose (30 kg P2 O5 /ha) + full dose of N and Potassic fertilizers K2 O (60:60 kg/ha) + FYM (12.5 tons/ha) + phosphorus solubilizing bacteria (PSB) or Vesicular Arbuscular Mycorrhizae (VAB) fungi (10 kg/ha) has been recommended for cassava. In Tamil Nadu, N:P:K fertilizers are applied in the ratio of 75:25:75 kg ha−1 under rainfed conditions for cassava. In Andhra Pradesh, the ratio is 60:60:60 kg/ha of N:P:K for rainfed conditions and 100:60:150 N:P:K under irrigated conditions. In Chattisgarh, the N:P:K ratio is 75:50:75 kg/ha. World soils, in particular Indian soils, are getting to be increasingly deficient in micronutrients, specifically Zinc. When there are micronutrient or secondary nutrient deficiencies detected, for instance that of Zinc, Boron and also Magnesium (though it is a secondary nutrient) they are applied as ZnSO4 , at the rate of 12.5 kg/ha, to correct Zn deficiency, MgSO4 to correct Mg deficiency and Borax (to correct Boron deficiency, 10 kg/ha). The lime-induced chlorosis in Tamil Nadu can be corrected by 1% ZnSO4 and FeSO4 sprays to the foliage of cassava plants. How best to irrigate cassava?: When the crop is grown as a rainfed one, as for instance in Kerala, no irrigation is provided, while irrigations are provided when it is grown as an irrigated crop, as for instance, in Tamil Nadu and Andhra Pradesh. It is the initial stage of crop establishment when sufficient soil moisture availability is crucial. Supplementary irrigation during drought period can increase tuber yield. Irrigation at approximately 25% available soil moisture depletion, throughout the growing season of the crop, could double the tuber yield control to control treatment. It also improves starch content and reduces HCN content. Interculture in cassava—weeding and earthing up: Both weeding and earthing operations are very essential for good crop growth. First weeding along with earthing up is done 45–60 days after planting and the second weeding a month later.

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Filling the gaps: When poor quality setts are used, all stakes may not properly establish in the field, which must be corrected by gap filling. For this, at the time of planting stakes in the main field, about 5% of the stakes may be planted separately at a very close spacing of 4 cm × 4 cm in a nursery. The plants, when they are 15–20 days old, are uprooted from the nursery which are used for gap filling. Is thinning of shoots necessary?: One finds vigorous sprouts emerging from the buds, which are more vigorous than those emerging from the lower nodes of the stakes. In such a case, removal of excess sprouts by nipping, 10–15 days after establishment of the plant help prevent mutual shading and intra-plant competition for nutrients and soil moisture is a must. Retention of two healthy shoots opposite to each other is preferable for the production of more number of tubers per plant. The cropping systems in cassava: Cassava being a short, perennial woody shrub is very suitable as an intercrop in different cropping systems. It is very popularly grown as an intercrop in coconut plantations widely in Kerala state. It can also be grown as an intercrop in Eucalyptus plantations, also with forest and fruit trees. Experience in Kerala State shows that up to five years, cassava can be successfully grown in a coconut plantation. Varieties, such as Sree Vishakam and Sree Sahya can be profitably used as an intercrop. Cassava variety KMC-1 has been found to be a very suitable intercrop in coconut plantations in the Kuttanad district of Kerala State. Cassava takes about nine to ten months to harvest, being a long-duration crop. Spaced at 90 cm × 90 cm, it takes about 3–4 months to develop enough canopy, due to slow initial growth, which provides a great opportunity to grow short-duration intercrops, such as, groundnut, vegetable cowpea, French bean, black gram or other legumes. In Tamil Nadu, black gram Bellary onion (Allium cepa), in Andhra Pradesh green gram/black gram, and in Assam soy bean and French bean are recommended as suitable intercrops in cassava cultivation. TMV-2 and TMV-7, which are bunch types of groundnut varieties, and French bean (cv. “Contender”, a cultivar), are promising and can be grown as economical intercrops. Sree Prakash and Sree Jaya have been found suitable for low land cultivation in a paddy-based cropping system, that is, sequential cropping of cassava and paddy. The cultivation details of various intercrops is given in Table 3. Higher gross income was achieved in the cassava intercropping systems with legumes/non legumes than the pure stand of cassava. The gross income increased by 40–82% in a cassava + French bean system, 25% in a cassava + urd bean system, 29% in a cassava + green gram or black gram system. Cassava can be successfully cropped following maize, peanut, sorghum, selected vegetables and banana (Ravi & Mohankumar, 2004).

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Table 3 Intercropping schedule in cassava Crop used as intercrop

Cultivar

Duration (Days)

Spacing (cm)

Row number

Seed rate (kg/ha)

NPK (kg/ha)

Yield (kg/ha)

Peanut

TMV-2

100

30 × 20

2

40–45 (kernel)

10:20:20

1200

Peanut

TMV-7

100

30 × 20

2

40–45 (kernel)

10:20:20

1200 (dry pod)

70

30 × 20

2

40

20:30:40

2000

French bean Contender Top cross

4

Cowpea for grain

S-488

90

30 × 25

2

20

10:15:10

800

Cowpea (vegetable)

B-61

65

40 × 20

1

88

10:15:10

3000

Source Varma et al. (1997)

Harvest and post-harvest management: Cultivar used in the field decides the harvest time. A short duration one can be harvested in about 6–7 months and a long duration harvested 10 months after planting. Delay in harvest in tuber deterioration which will adversely affect cooking quality. How much yield to expect?: The final tuber yield depends on the cultivar used and stage of harvest. Long duration cultivars, of about 10–11 months, yield close to about 40 tons/ha and short duration ones (6–7 months) yield close to 30 tons/ha. Yams: What are the environmental requirements of yams, especially soil and climate?: Ideally a neutral (pH 5–7), friable sandy loam soil containing adequate amount of organic carbon is suitable for yams. Yams are relatively drought tolerant, but, better yields are obtained with supplemental irrigation. Warm climate (25–30 °C, ambient temperature) and adequate soil moisture are deal for good yam growth. Yam cannot tolerate frost and growth is adversely affected below 20 °C. At early stages of growth long duration (12 h) photoperiod favors good vine growth, while short duration photoperiod favors satisfactory tuber production. What planting materials to use and how to propagate?: Whole small tubers, or pieces of tubers, constitute the planting materials for yam, as the crop is propagated vegetatively. Large whole yams are cut into “setts” (small pieces, as in the case of cassava), consisting of tops, middles and bottoms, while small tubers are planted as such. The small tubers (seed yams) and preferred for their earliness in maturity, and, uniformity of sprouting. The average weight around a quarter kilogram tuber is optimum for the cultivation of Dioscorea alata and D.

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rotundata, whereas about 125 g is ideal for D.esculenta. Yam tubers remain dormant in storage, during two to two-an-a half months, and hence, quick dipping in 8% solution of ethylene dichlorohydrin followed by dry storage is used to break dormancy of the tubers. Vine cuttings are also used as propagation materials And this is, in particular, useful for rapid multiplication of desirable clonal material, but, tuber production through this method is slow. When to plant?: Planting generally is done during the latter part of summer, from March to May, and when summer showers are received the tubers start germinating. Planting Method: The soil type decides the planting method. Both flat and raised beds are used. In heavy soils ridges or mounds are made on which the planting material is planted. Ridge planting is done on slopy and to conserve soil from erosion due to heavy rains. How to space the plants and ensure optimum density?: Both Dioscorea alata and Dioscorea rotundata require wider spacing, because both grow luxuriously and leaves are very broad. Planting at 1 m × 1 m total a density of 10,000 plants ha−1 . With 90 cm × 90 cm spacing the density works to 12,000 plants ha−1 . For Dioscorea esculenta, a closer spacing of 75 cm × 75 cm is preferred which works to 18,000 plants ha−1 . What is the optimum fertilizer schedule?: Plain cattle manure, compost or Farm yard Manure (FYM) at the rate of 10 tons−1 is recommended at the time of field preparation. For Dioscorea esculenta NPK should be applied in the ratio of 80:60:80 and for Dioscorea alata and Dioscorea rotundata the ratio is 100:60:80 for NPK, respectively. The whole of phosphorus and half of nitrogen and potassium are applied at planting time. The remaining dose of nitrogen and potassium is applied again in two splits of equal doses when the crop is first earthed up and weeded. How best to irrigate yam?: Yam is relatively tolerant to drought, supplemental irrigation, provided immediately after planting to ensure uniform sprouting and establishment of the crop helps the crop very much, ensuring quick sprouting and subsequent establishment. During dry period before the onset of monsoon irrigation is done to ensure soil moisture. Yams are very sensitive to waterlogging. Interculture—weeding and earthing up: Weeding and earthing up should be done a week after when the crop sprouts. A month later the second weeding and earthing up is done. It takes up to 40 days to see the first sprouts. Critical stages for weed interference in yams coincide with the growth phases when leaf development and tuber bulking are maximum.

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Is it necessary to mulch yam crop?: Following planting of tubers or setts, mulching is done. The mulch protects soil from excessive water evaporation ensuring quick sprouting and plant establishment. It also checks weed growth. These, lead to good tuber yield How to stake the crop?: The yam crop must be staked, to enhance tuber production, which exposes the plant to more sunlight leading to greater photosynthesis. Emerging should be provided artificial supports to prevent injury to the tender shoots. Dioscorea alata and Dioscorea rotundata plants trail to about 4 m high, whereas Dioscorea esculenta requires only lesser heights for staking. In Andhra Pradesh, Dioscorea alata was found growing without staking, as in the case of sweet potato. The system of cropping pattern: A good example where crop rotation and inter cropping leads to higher income is seen in Bihar state where the yam–wheat–green gram and yam–potato–green gram cropping sequence or maize intercropped with yam brought in good income to the farmer. Is intercropping practiced?: In Maharashtra State of India, in the Dapoli and Konkan regions, yam is grown in cashew plantations; and the variety grown is Kanchan giving a tuber yield of about 20 tons ha−1 . Dioscorea alata can be successfully and profitably grown as an intercrop in Banana plantations, as shown in Kerala State. Harvest and post-harvest management: The species and varieties of yam decide the harvest date. Yam crop is generally harvested after about 7–9 months following planting, based the species and varieties grown. Dioscorea esculenta matures earlier than other species. Leaf yellowing and complete drying up of the vines indicates that the crop is mature and ready for harvest. Two general practices are adopted for harvest, as follows: 1. Single harvest: Only harvested once (complete uprooting of the tubers once only). 2. Double harvest: Consists of removing the mother tubers after two months of growth, allowing subsequent production of side tubers, which are harvested alter. But, the double harvesting is less economical compared to single harvesting. Colacasia: Soil and climatic requirement: The colacasia crop thrives best in well drained sandy loam soil in a pH range of 5.5–7.0. It is grown in alluvial and fertile soil, while in upland conditions, it can also thrive well in marginal land. Colacasia requires a continuous supply of water. The crop prefers moist conditions for better growth and yield; best suited in a swampy condition with ambient temperature ranging from 5 to 30 °C. In moist environment

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it can also grow under lower ambient temperature. Annual optimum rainfall must be around 100 cm. The crop has found to grow well in flooded conditions in Hawaii. How to select planting material and propagate colacasia?: The following are the two types for which the details are provided below: Taro: Eddoe Type: Either mother corms or cormels constitute the planting material. When mother corms are used for propagation, sucker production was higher. Using cormels resulted in higher tuber yield. For planting Eddoe type, cormels weighing about 25 g are used, especially in upland conditions. Disease and pest infection—free healthy cormels uniformly—sized are selected and stored in a cool well ventilated room at least three months before planting. Cut pieces of corm can be used as planting material. Bunda: Dasheen Type: Transversely cut pieces, of 4–5 cm thickness having one or two buds, weighing less than 50 g, of the main corm, are used as planting material. For healthy sprouting, the top portion of the main corm containing the apical bud is preferable. Often, the daughter corms are also sed as planting material. Like in the case of the Eddoe Type, healthy, infestation and injury free planting mating material is selected and stored in a cool and well ventilated room for 3 months, prior to plating. In the case of Swamp Taro, long runners of the roots are the edible starchy part. Eddoe Type Taro: Planting Material: Normally rainy season is preferred, but, can also be grown under irrigated conditions. Summer rain season (April–May) is the ideal time to plant Eddoe Type taro in Kerala State. In North and Eastern India, when the crop is irrigated, it is planted in February and when rainfed it is planted in June. Method of Planting: For Eddoe type, flat bed planting is preferred to conserve soil moisture; it can also be planted on the ridge and furrow method. Shallow trenches, at a distance of 45–60 cm are made in the flat bed method, while the cormels are placed at a distance of 30 cm, which is then covered with soil. When the plants grow, soil should be heaped at the base of the plant during the earthing up operation which will enable ridges to be made. What seed rate to use and space the plant?: Three factors, namely, the size of the planting material, inherent soil fertility, and, availability of adequate soil moisture will decide the spacing or planting. Optimum yields were harvested using a planting space of 60 cm × 45 cm, 60 cm between rows and 45t cm between plants This ensures optimum plant density. Higher plant density can be obtained by resorting to closer spacing, namely, 45 cm × 30 cm.

3 What are the Precise Aspects of Crop Management, Post-harvest … Table 4 The AICRPTC recommendations for colacasia

Indian state/Region

Recommended NPK kg ha−1

Assam

80:60:120

Andhra

120:60:120

Bihar

80:60:80

Karnataka

60:60:90

Tamil Nadu

40:60:120

Uttar Pradesh

80:60:80

31

Spacing and Seed Rate: The size of planting material, the inherent fertility status of the soil and the soil moisture status determine the spacing and seed rate. For optimum yield and economic returns, a spacing of 60 cm × 45 cm has been found optimum with optimum plant density at 37,000 plants ha−1 , and on marginal fertility land higher plant density can be attained with closer planting spaced at 45 cm × 30 cm, which works out to 74,000 plants ha−1 . The depth of planting varies between 5 and 10 cm, depending on the size of the planting material. What about the fertilizer schedule?: At the time of land preparation for sowing farm yard manure (FYM) at the rate of 10–15 t ha−1 is recommended which will help make the soil friable. NPK in the ratio of 80:80:120 kg ha−1 is applied. Full dose of phosphorus with half dose of nitrogen and potassium should be applied in two split doses, the first within one week to ten days after sprouting and the second dose a month later. Available scientific reports suggest combined application of N, P and K at the rate of 80:25:100 kg ha−1 highly beneficial for optimum crop growth and ultimate yield. Most of the researchers opine that while nitrogen and potassium should be applied in split doses, the recommended dose of phosphorus should be applied at the time of planting. However, significantly higher yield has been obtained in the case of there split application of nitrogen and potassium (Ravi & Mohankumar, 2004). The fertilizer schedule has been perfected by the All India Crop Improvement Project For Tuber Crops (AICRPTC). A summary is provided in Table 4. Use of Biofertilizers: The used of biofertilizers is attracting more and more attention in many crops, and, colacasia is no exception. In the case of colacasia it was indicated that VAM (Vesicular Arbuscular Mycorrhizae, VAM) fungi help in the higher uptake of phosphorus by solubilizing soil phosphorus near root vicinity, by fungal hyphae. In Andhra Pradesh, application of half the recommended dose of phosphorus (30 kg ha−1 + full dose of nitrogen (120 kg ha−1 − and 120 kg K ha−1 + VAM fungi @ 10 kg ha−1 having a spore load of 400 spores 10 ml−1 + phosphorus solubilizing bacteria @ 10 kg ha−1 has been recommended for taro.

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How best to irrigate colacasia?: Inherent soil moisture or applied irrigation water both affect tuber yield in colacasia. Normally seven to eight irrigations are required for good tuber yield. When soil moisture is limiting vegetative growth is adversely affected, consequently tuber yield. The Eddoe Type grows well in moist conditions. Relatively, the Eddoe Type requires lesser amount of water compared to the Dasheen Type since the former is of a shorter duration. Also, Eddo Type is more tolerant to drought conditions compared to the Dasheen Type. Interculture in colacasia—weeding and earthing up: When weed-free colascaia plants thrive. Ideally, two manual weedings along with earthing up is provided to ensure good crop growth. The first weeding along with earthing up is done about a week later after sprouting and the second one a month later. Inasmuch as chemical weed control is concerned, application of atrazine or simazine @ 1 kg ha−1 along with one earthing a later stage of crop growth has been found to be quite effective in weed control resulting in good crop growth and tuber yield. Is it necessary to mulch colacasia?: Soil mulch has been found to be quite beneficial in taro, as it conserves soil moisture and provides shade to the crop. In Meghalaya (India) black polythene mulching effectively controlled weed growth, resulting in a tuber yield of 22.7 t ha−1 in Colacasia variety Kandha-5. The need to desucker: When the colacasia plant produces a large number of suckers, it leads to reduction in tuber size, consequently, tuber yield. Hence, the operation of desuckering is very important in ensuring good tuber yield in colacasia. For this, only 3 suckers should be retained at second earthing up. The different cropping systems in colacasia: Different cropping systems are followed in colacasia. Table 5 summarizes the different cropping systwemas in colacasia. Dasheen Type (Bunda): Ideal planting time: Planting time in India varies greatly from region to region in India and the availability of irrigation is a prime consideration. Planting can be done from February to June, during the year, but, February is the ideal month to plant, if there is assured irrigation, especially for planting in North Bihar State, parts of West Bengal and Eastern Uttar Pradesh. The crop can also be planted in June, when there is no frost during the growth period.

3 What are the Precise Aspects of Crop Management, Post-harvest …

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Table 5 Summary of the different cropping systems in colacasia Indian state

Cropping system

Assam

Green gram and okra as intercrops

Uttar Pradesh

Green chilli as intercrop, colacasia followed by Tomato, colacasia + ridged gourd, Colacasia-cauliflower, Colacasia (variety Kadma local) + cowpea (Arka garima) combination is the most profitable intercropping system in Uttar Pradesh

Bihar

Intercropping of three rows of onion in between two rows of colacasia has recorded an additional net return of INR 20,000 under irrigated conditions

Kerala

Taro is recommended as an intercrop in banana/coconut/arecanut plantations

Which is the ideal planting method?: Both planting methods, ridge and furrow, and also flat bed, are practiced, the flat bed method is adopted under upland conditions where there is good drainage. Furrow method is preferable as it conserves soil moisture. In well prepared land, the trenches are usually made at a distance of 60–75 cm. Plant to plant distance is kept at 30–45 cm. What seed rate to use and how to space the plants? Compared to the Eddo Type, the Dasheen Type is generally taller, spreading and robust in structure. Spacing for Dasheen Type is wider than that used in the case of Eddoe Type. A spacing of 75 cm × 75 cm or 75 × 30 cm is optimum for the Dasheen Type to harvest good yield and obtain good profits. Closer planting, namely, 60 cm × 45 cm or 60 cm × 30 cm can be followed, in soils less fertile and heavy. Seed requirement varies with different spacings. About 1.5 tons ha−1 is required with optimum spacing, whereas with closer spacing the seed rate increases to about 2.5 ha−1 . What is the optimum fertilizer schedule?: Fertilizer schedules for both Eddoe and Dasheen are similar. In Bunda Type (Colacasia easculenta var. esculenta), seed size of 40–5 kg ha−1 along with the application of N @100 kg ha−1 and 60 kg of P and 120 kg of K ha−1 is applied to obtain optimum yield. How best to irrigate colacasia?: Since Dasheen Type is longer lasting than Eddo Type, its water requirement is more. Normally, 8–10 irrigations are required for optimum yield if planting is done in summer. Compared to the Eddoe Type, Dasheen Type is more drought sensitive. Interculture in colacasia—weeding and earthing up: As Dasheen Type is of longer duration than the Eddoe Type, it requires three weedings coupled with earthing up. Initial weeding is preferred as it facilitates good

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establishment and growth of the crop. Weeding a week after sprouting is recommended in places where weed infestation is acute. Atrazine or simazine @ kg ha−1 can be applied in early stages followed by two light earthing up operations when the crop is planted as flat ed method. When Dasheen is planted as ridge and furrow method initial earthing up is essential. Is mulching in colacasia necessary?: Use of organic mulches, such as, straw, grass, dried leaves, is beneficial in soil moisture conservation. Mulching also ensures quick germination. Is there a need to desucker incolaasia?: In the case of dasheen Type, desuckering is not warranted. Harvest and post-harvest treatment: Colacasia matures I about 4–5 months. However, tuber dry matter increases up to 6 months. Eddoe Type is harvested earlier than Dasheen Type and leaf—drying is the indicator that crop is ready for harvest. Yield: Can vary from 20 to 40 tons ha−1 , depending on variety, type, crop management and stage of harvest. Marketing: Prior to marketing, mother corms and cormels should be separated. In Dasheen Type mother corms are marketed, while in Eddo Type cormels. Storage: Right at the beginning, damaged tubers should be separated from good ones and dried in shade. Drying should be done for a day and sticking soil on tubers be removed. Mixing both, good tubers and damaged ones, will adversely affect marketability. Both soil pits and heaping can be adopted in storing colacasia, but, when stored in storage rooms, good ventilation must be ensured or else the tubers will spoil. Good ventilation will also ensure the tubers free of pest attack. Swamp Taro: Colacasia esculenta var. stoloniferum Colacasia esculenta var. stoloniferum is a type of colacasia that is extensively grown in the swampy conditions of Eastern and North Eastern India, in parts of Assam and West Bengal. Planting is in January where mother corms are used. NPK in the ratio of 300:100:200 kg ha−1 is used, along with 5 irrigations, as advocated by Bidan Chandra Krishi Viswavidyalaya (BCKV), Kalyani, West Bengal, India. Harvest is at fortnightly intervals starting from April. Stolons are about a meter long and the crop yields vary from about 20–26 tons ha−1 and fortnightly yield varies from 1 to 3 tons ha−1 . BCST-1, BCST-5, BCST-13 and BCST-14 are good selections and

3 What are the Precise Aspects of Crop Management, Post-harvest …

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high yielders. Application of Mahua cake @ 5 kg N ha−1 + 225 kg N ha−1 through urea fertilizer produced significantly higher stolon yield of about 20.86 tons ha−1 , at Kalyani, West Bengal State. Tannia: Xanthosoma What are the ideal soil and climatic requirements?: Well-drained, sandy loam with pH in the neutral range (5.5–7.0) soil is most suitable for Tannia cultivation; however, the crop adapts well to different soils. The exception is clayey soil. Both long dry spell and waterlogging adversely affects the tannia plant. Well distributed rainfall in the range of 150–200 cm and hot and humid conditions with ambient temperature ranging from 25 to 30 °C are most suitable for the Tannia crop. It can neither withstand cold climate nor frost and can grow well up to an elevation of 1500 m above mean sea level. Planting Material: As in the case of colacasia, both mother corms and cormels are used as planting material. Healthy cormels of bigger size, 50–80 g weight and 20–25 cm long are recommended for planting. However, when corms are used for planting, setts from the top portion of the main corm with a thickness of 5–10 cm containing the apical bud is preferred. In general, the plants grown from the apical portion require shorter growing period than those plants propagated from the other portions of the main corm. Planting Time: Xanthosoma is planted with the onset of monsoon, which is April–May months, under rainfed conditions, but, with assured irrigation, the crop can be grown throughout the year. Planting Method: Xanthosoma can be planted on ridges as well as on flat bed, but, ridge planting gives higher tuber yield as compared to flat planting system. What spacing and seed rate to use?: A spacing of 90 cm is used between plants on ridges. When the crop is grown for leaf purpose, it should be planted on both sides of the raised bed of 1 m breadth and convenient length. Bed height should be 30 cm. Around 8–10 quintals (1 quintal = 100 kg) of corm is required to plant one hectare. Further intercultural practices like weeding, earthing, are the same as in the case of colacasia. What is the fertilizer requirement?: NPK in the ratio of 80:60:80 kg ha−1 along with 15t tons of FYM ha−1 as a basal application at planting time

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Is the plant intercropped?: In sapota orchard tannia is grown as an intercrop. Also it can be grown as an intercrop in banana and coconut plantations What about harvest and post-harvest management?: About ten months after planting, when older leaves turn yellow in color the crop is ready to harvest. Unharvested corms can remain on the plant up to about three months after maturity. After maturity, leaves must be speedily harvested, when the crtop is grown for its leaves. Up to 50 leaves can be harvested. Where leaves are only harvested for Patra, as in Maharashtra, Goa and Gujarat, the corms and cormels are used as planting material. After 45 days since sprouting, the leaves are harvested each day. Yield: The crop yield about 30 tons ha−1 of corms if the crop is grown only for corms. Removal of leaves adversely affects corm production Storage and marketing: Curing in sunlight of corms and cormels, for about 4–5 days, after removal of damaged ones, enhances their marketability and storability. Tubers can be spread on sand and stored in well-ventilated rooms with low humidity, where they keep well. Giant Taro: What are the soil and climatic requirements?: In well drained soils, the crop can grow well in medium to heavy textured soils. Quite often one sees the plant growing naturally, along river banks and canals, but, it cannot withstand waterlogging. It performs well in sandy loam soil, with proper irrigation. Long drought adversely affects tuber formation as the plant is very sensitive to heat in the ambient atmosphere. As it is a tropical crop it cannot tolerate temperature below 10 °C, when vegetative growth and tuber development are adversely affected. Areas with high and well distributed rainfall, temperature ranging from 25° to 30 °C are most suitable. Propagation and Planting Material: Alocasia is propagated through suckers, but, shoot tips with a bit of stem portion having a few buds can also be used as planting material. Planting Time: Mach to May, before the onset of south-west monsoon is ideal planting time Planting Methods: Planting is done in holes where corms/cormels are planted about 15 cm deep while suckers are planted about 15–20 cm deep.

3 What are the Precise Aspects of Crop Management, Post-harvest …

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Spacing: Spacing can vary from 0.6–1.5 × 0.6–1.5 m. It can also be intercropped with Dioscorea species, spaced 3.5 × 3.5 m. As a single crop, all intercultural operations shoud be done as required, while as an intercrop intercultural operations for Dioscorea are sufficient for Alocasia, as well. Normally, all intercultural operations resemble those in Colacasia. Harvest: The crop matures in about 18 months, and it can remain without spoilage in the field for three months after maturity. Elephant Foot Yam: What are the soil and climatic requirements?: Fertile, well drained, sandy loam is preferred of pH slightly acidic (