Fertigation: A Pathway to Sustainable Food Production: Basics and Applications (SpringerBriefs in Environmental Science) 3031055950, 9783031055959

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Ahmed Mohamed Taha

Fertigation: A Pathway to Sustainable Food Production Basics and Applications

Ahmed Mohamed Taha Soils, Water, and Environment Research Institute Agricultural Research Center Giza, Egypt

ISSN 2191-5547 ISSN 2191-5555 (electronic) SpringerBriefs in Environmental Science ISBN 978-3-031-05595-9 ISBN 978-3-031-05596-6 (eBook) https://doi.org/10.1007/978-3-031-05596-6 © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 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 would like to dedicate this work to all the professors who supervised me in the early stages of my education and career. These professors guided and assisted me until I reached this stage of my working life. One of these professors is Prof. Hamdy El-Houssainy Mohamed Khalifa (former Manager of the Soils, Water and Environment Research Institute at the Agricultural Research Centre, Egypt), who generously contributed his great knowledge to help bring about the emergence of generations of scientific excellence. Furthermore, he spared no effort to help in reviewing this book and providing his advice to improve its quality. To him I dedicate this book.

Preface

Sustainable food production entails the use of smart practices to improve the quantity and quality of crops. Efficient and effective water and fertilizer use, especially at the farm level, was identified as an important contributory factor in the strategy required to address problems of water scarcity and practising intensive agriculture. Fertigation is one of these practices. It is the application of dissolved mineral fertilizers, soil amendments and other water-soluble products to the roots of crops through irrigation water. Fertigation is directly related to pressurized irrigation systems and water management. Drip and micro-irrigation systems, which are highly efficient for water application, are most suitable for fertigation. Water-soluble fertilizers at concentrations required by crops are conveyed through the irrigation stream to the wetted soil. This reduces water and fertilizer application. Fertigation is an agro-technique that provides an excellent opportunity to minimize environmental pollution by increasing fertilizer use efficiency with the required amounts and increasing the return on the fertilizer invested. Understanding the basic issues regarding the appropriate selection of fertilizer compounds used in fertigation for growing various field and horticultural crops is essential in order to attain higher productivity, increase food security and reduce food contaminations. It also largely contributes to increasing water use efficiency and water productivity. This book introduces the basic and practical information on fertigation to researchers, extension agent and growers, and aims to provide an understanding of the basic issues regarding the appropriate selection of fertilizer compounds used in fertigation for growing various field and horticultural crops. It clarify the advantages of fertigation and sets out solutions to overcome its disadvantages. In Chap. 1, chemigation and fertigation definitions, advantages, disadvantages and potential risks are introduced in a way that will be easy for readers to follow. In order to sustainably practise fertigation, it is essential to take the proper intervention measures, including physical and chemical soil characteristics, soil topography, irrigation systems used and cultural practices followed. All these practices are explored in depth in this chapter. The importance of the distribution uniformity of irrigation water and its effect on the efficiency of fertigation is also explored.

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In Chap. 2, the methods of selecting an injector for efficient fertilizer/chemical injection and the equipment required to apply chemicals through an irrigation system are described. Different types of injectors used at the field level, their advantages and disadvantages, details of the injector and methods of operation are presented. Frequent maintenance and calibration to ensure optimal injector performance and the production of healthy crops are discussed. In Chap. 3, the types of suitable and compatible fertilizers for fertigation,— namely, the types of water-soluble fertilizers—are specified. The chapter also classifies soluble solid and liquid fertilizers suitable for fertigation, depending on their availability, profitability and convenience. The chemical properties that should be followed in order to determine the solubility of certain fertilizers are also reviewed. The factors that determine the suitable fertilizer for a specific application are reviewed. In Chap. 4, the effect of major, secondary and micronutrients used in fertigation on soils and plants for sustainable management and higher production under open field conditions are identified. This chapter covers the types and forms of fertilizers and the basic considerations that should be borne in mind when using N, P and K fertilizers in fertigation. The movement of macronutrients in the soil profile and the uptake by plants at different physiological stages are also covered. The effect of soil pH on nutrients availability to plants is also discussed. Chapter 5 reports the results of several field studies on field crops (cereals, leguminous, sugar, oil and fodder), horticultural crops (fruits and vegetables), medicinal and aromatic plants, and cut flower plants. The effect of fertigation practices using pressurized irrigation systems (sprinklers and drips) on the above-mentioned crops in Egypt is also discussed. Giza, Egypt

Ahmed Mohamed Taha

Contents

1 Introduction to Chemigation and Fertigation . . . . . . . . . . . . . . . . . . . . . 1.1 Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Disadvantages and Potential Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Factors Affecting Chemigation and Fertigation . . . . . . . . . . . . . . . . 1.3.1 Irrigation System Characteristics . . . . . . . . . . . . . . . . . . . . . 1.3.2 Soil Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.3 Topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 2 3 5 5 9 10 10

2 Selecting an Injector for Fertilizer/Chemical Injection . . . . . . . . . . . . . 2.1 Fertigation Injectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 The Chemical Supply Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Venturi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Piston Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 The Hydraulic Piston Motor Injector (Hydraulic Energy) . . . . . . . . 2.6 Diaphragm Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Electric Dosing Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 13 14 16 18 19 21 23 24

3 Fertilizers for Fertigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Forms of Fertilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Suitability of Fertilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 Solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Acidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Compatibility of Fertilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25 25 27 27 30 31 31 33

4 Major, Secondary and Micronutrient Fertilizers Used in Fertigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Major Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Nitrogen (N) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

35 35 35

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4.1.2 Phosphorus (P) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.3 Potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Secondary Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Sulphur (S) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Micronutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Micronutrient Forms Used in Fertigation . . . . . . . . . . . . . . 4.3.2 Micronutrients Availability as Related to Soil pH . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41 45 48 48 50 51 52 52 53 53

5 Fertigation Practices: An Egyptian Case Study . . . . . . . . . . . . . . . . . . . . 5.1 Field Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Barley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 Chickpea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 Faba Bean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.4 Maize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.5 Wheat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Intercropping Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Sunflower with Peanut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Sugar Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.1 Sugar Beet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Oil Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 Canola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.2 Canola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.3 Peanut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.4 Rapeseed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.5 Sunflower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Fodder Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.1 Alfalfa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.2 Cowpea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.3 Fodder Beet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.4 Fodder Beet (Voroshenger Var.) . . . . . . . . . . . . . . . . . . . . . . 5.5.5 Pearl Millet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.6 Sudan Grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Chai, Foino, Niger and White Perilla Crops (New Crops Grown in Egypt) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.1 Chia Crop (Salvia hispanica L.) . . . . . . . . . . . . . . . . . . . . . . 5.6.2 Fonio Millet (Digitariaexilis Stapf) . . . . . . . . . . . . . . . . . . . 5.6.3 Niger (Guizotiaabyssinic a (L. F.) Cass.) . . . . . . . . . . . . . . 5.6.4 White Perilla Crop (Perilla Frutescens, Family Lamiaceae) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Fibre Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.1 Cotton (Sandy Soil) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.2 Cotton (Calcareous Soil) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

57 57 57 58 58 59 60 61 61 62 62 63 63 64 64 65 66 66 66 67 67 68 68 69 70 70 71 72 72 73 73 74

Contents

5.8

Orchards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.1 Perennial Orchards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.2 Deciduous Orchards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9 Vegetable Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.1 Cabbage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.2 Cantaloupe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.3 Cucumber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.4 Eggplant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.5 Garlic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.6 Hot Pepper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.7 Lettuce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.8 Okra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.9 Onion Crop (Sandy Soil) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10 Medicinal and Aromatic Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.1 Coriander Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.2 Lemongrass (Cymbopogoncitratus) . . . . . . . . . . . . . . . . . . . 5.10.3 Licorice Extract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11 Cut Flowers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11.1 Zinniaelegans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12 Future Trends in Fertigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xi

75 75 86 90 90 90 91 91 92 93 94 95 95 102 102 103 104 105 105 105 106

Fertigation Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Uncited References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

List of Figures

Fig. 1.1 Fig. 1.2 Fig. 2.1 Fig. 2.2 Fig. 2.3 Fig. 2.4 Fig. 2.5 Fig. 2.6 Fig. 2.7

Fig. 2.8 Fig. 2.9

Fig. 2.10 Fig. 2.11 Fig. 5.1 Fig. 5.2 Fig. 5.3

Fig. 5.4

Schematic drawing of typical irrigation pipeline check valve . . . The effect of soil texture on the wetted area around emitters . . . . The chemical supply tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Injected concentration over time using a chemical supply tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Venturi injector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Injected concentration over time using a venturi injector . . . . . . . The piston pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Injected concentrations over time using a piston pump . . . . . . . . The hydraulic piston motor injector: a piston pump—suction stroke; b piston pump—discharge stroke; c double acting piston pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The diaphragm pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cross-section drawing of the pump mechanism for a diaphragm-type chemical injection pump (Poynton 1983) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of electric dosing pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . Injected concentrations over time using electric dosing pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maize crop grown in sandy soil using the drip irrigation system (Taha 2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wheat crop grown in sandy soil using the sprinkler irrigation system (Taha 2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chia plants at a the development stage and b the flowering stage in sandy soil under drip irrigation (Taha and Khalifa 2021, unpublished data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Niger growth stages: a initial stage, b development stage, c flowering stage and d maturity stage (Taha and Khalifa 2021, unpublished data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 10 14 15 17 18 18 19

20 21

22 23 24 59 61

71

73

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xiv

Fig. 5.5

Fig. 5.6 Fig. 5.7

Fig. 5.8

Fig. 5.9

Fig. 5.10

Fig. 5.11

List of Figures

The maturation stages of Date palm fruits: a pollination, b Hababouk, c Kimri, d Pre-Khalal, e Khalal and f harvest (Taha and Khalifa 2021, unpublished data) . . . . . . . . . . . . . . . . . . Mango fruits during harvesting according to farmer’s practice (Taha 2020) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Olive growth stages: a initial stage, b development stage, c and d flowering stage, e and f maturity stage, and g, h, i and j harvest (Khalifa and Taha 2021, unpublished data) . . . . . . Olive growth stages: a initial stage, b development stage, c and d flowering stage, e and f maturity stage, and g and h harvest (Taha and Khalifa 2021, unpublished data) . . . . Pomegranate fruits during harvesting grown under the farmer practice and the 120% ETo irrigation treatment and the application of fertilizer in 80% of the irrigation time (Taha 2018) . . . . . . . . . . . . . . . . . . . . . . . . . Field implementation of alternating irrigation on an onion crop in calcareous soil under a drip irrigation system (Taha et al. 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Field implementation of alternating irrigation on a tomato crop in calcareous soil under a drip irrigation system (Abd El-Halim 2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

78 79

82

85

89

97

101

List of Tables

Table 3.1 Table 3.2 Table 3.3 Table 4.1 Table 4.2 Table 4.3 Table A.1 Table A.2 Table A.3 Table A.4 Table A.5 Table A.6

Table A.7

The effect of chemical form, soil pH and temperature on the solubility rates of fertilizers . . . . . . . . . . . . . . . . . . . . . . . . The effect of fertilizer solutions on the relative corrosion of various metals (after Boman and Obreza 2012) . . . . . . . . . . . Compatibility of fertilizers for fertigation . . . . . . . . . . . . . . . . . . Secondary nutrients, their uptake forms, and their mobility in soil and plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Secondary nutrients contained in fertilizers . . . . . . . . . . . . . . . . . Micronutrients and their availability related to soil pH (Soil Fertility Manual 2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nutrient requirements per ton of crop yield produced . . . . . . . . Macronutrient (N, P and K) requirements for some filed crops in the newly reclaimed sandy soils . . . . . . . . . . . . . . . . . . . Macronutrient (N, P and K) requirements for fibre crops in the newly reclaimed sandy and calcareous soils . . . . . . . . . . . Macronutrient (N, P and K) requirements for some fruit crops in the newly reclaimed sandy soils . . . . . . . . . . . . . . . . . . . Macronutrient (N, P and K) requirements for some vegetable crops in the newly reclaimed sandy soils . . . . . . . . . . Macronutrient (N, P and K) requirements for some medicinal and aromatic plants in the newly reclaimed sandy soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Macronutrient (N, P and K) requirements for some cut flowers in the newly reclaimed sandy soils . . . . . . . . . . . . . . . . .

28 32 33 48 49 53 112 116 119 120 122

124 125

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Chapter 1

Introduction to Chemigation and Fertigation

Abstract It is widely recognized that chemigation and fertigation use has increased recently under pressurized (sprinklers and drips) irrigation systems in the world. In this chapter, the definitions, advantages, disadvantages and potential risks of chemigation and fertigation are introduced in a simple way that will make it easy for readers to follow. For sustainable agriculture management using fertigation practice, it is essential to take the proper intervention measures, including physical and chemical soil characteristics, soil topography, irrigation systems used and cultural practices followed. The importance of the distribution uniformity of irrigation water and its effect on the efficiency of fertigation is also considered. Keywords Chemigation · Fertigation · Advantages · Disadvantages · Irrigation systems · Soil characteristics · Distribution uniformity The term ‘chemigation’ is used here to describe the application of agrochemicals, including fertilizer, livestock waste, herbicides, insecticides, fungicides and other chemicals, via an irrigation system. This term is sometimes used interchangeably with fertigation. However, chemigation is considered to be a more restrictive and controlled process, due to the potential nature of the products being delivered, i.e. pesticides, herbicides and fungicides, which may cause harm to humans, animals and the environment. Therefore, chemigation is in general subject to more regulation than fertigation. Fertigation is the application of dissolved mineral fertilizers, soil amendments and other water-soluble products to the roots of crops through irrigation water. In other words, it is the combination of fertilization with irrigation and the steady supply of nutrients to the entire food crops landscape. It uses the irrigation system to deliver and slowly provide the required quantity of fertilizer that is estimated accurately through mechanical irrigation systems such as sprinklers and drippers. It is also defined as the practice of supplying crops in the field with fertilizers via the irrigation water (Bar-Yosef 1991). Fertigation, a modern agro-technique, provides an excellent opportunity to maximize yield and minimize environmental pollution (Hagin et al.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 A. M. Taha, Fertigation: A Pathway to Sustainable Food Production, SpringerBriefs in Environmental Science, https://doi.org/10.1007/978-3-031-05596-6_1

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1 Introduction to Chemigation and Fertigation

2002) by increasing fertilizer use efficiency, minimizing fertilizer application and increasing the return on the fertilizer invested. Fertigation practices Is defined as the application of proper concentration of nutrients via irrigation water using some types of injectors to meet crop needs throughout the growing season. Fertilizers applied through selected irrigation systems—‘surface, drip, subsurface drip and sprinkler’—proved to be more efficient than broadcasting fertilizer (Arnaout 1999). In fertigation, the timing, amounts and concentration of fertilizers applied are easily controlled. The fertilizer solution is injected into the desired irrigation water and at a carefully calculated rate. When the fertilizer solution is injected to a microirrigation system, the fertilizer is carried with irrigation water directly to the plant root zone. Fertilizer is generally available in dry suspension or solution form. When using dry material only, completely water-soluble compounds should be used for fertigation. Organic and synthetic fertilizers are both commonly used in fertigation and, in some cases, other soil enhancements are added as well. A few rules should be followed to achieve the maximum benefits of fertigation (Arora et al. 2015): 1. 2. 3. 4.

5.

The type and amount of fertilizers used must be soluble enough to dissolve completely in the fertilizer tank water. A completely pressurized drip irrigation system is required before fertigation begins. The fertilizers should be injected ahead of the filters to ensure that any undissolved particles are filtered out before the fertilizer enters the drip laterals. The period of time in which the fertilizer is injected into the system must be at least as long as that required to bring the entire drip irrigation system up to full pressure. This will allow each dispensing orifice in the drip line to have the same contact time with the fertilizer solution as it passes through the system. All fertigation units should be wired to the pump switch control or a flow control switch in the main line in order to prevent the unit from running when no water flows in the line.

1.1 Advantages Fertigation is used extensively in commercial agriculture and horticulture vegetables, greenhouses and ornamental plants, and is starting to be used in general landscape applications as distributor units become more reliable and easy to use. There are several benefits to this method of fertilization: It is used to spoon-feed additional nutrients or correct nutrient deficiencies detected in plant tissue analysis. • It is usually practised with high-value crops such as vegetables, turf, fruit trees and ornamentals.

1.2 Disadvantages and Potential Risks

• • • • • • • • • •

• • • •

3

It ensures a uniform flow of water and nutrients. It reduces soil compaction. It reduces mechanical damage to crops. It reduces operator hazards. It ensures the potential reduction of chemical requirements. It ensures the potential reduction of adverse environmental impacts. It reduces farm costs compared to the cost of ground or aerial application. It provides the continuous feeding of nutrients at levels that encourage optimal plant health. This slow, steady delivery of nutrients can result in hardier plants that are less susceptible to drought and disease. It provides labour and energy cost savings—the only labour required is replenishing the supply of fertilizer in the system, monitoring plant health and making the necessary adjustments. It results in less waste, as nutrients are immediately available to plants in quantities they need. Therefore, lower concentrations of fertilizers are delivered at a rate that can be easily absorbed by plants, and smaller amounts of product are needed overall to do the job. The amount and form of the nutrient supply is regulated according to the need of the critical stages of plant growth. It provides water savings—plants that are given a continuous supply of nutrients tend to develop stronger root systems that are able to take in and absorb water more effectively, so they stay green and healthy despite the use of less water. It provides a better yield and quality of products obtained. The acidic nature helps in cleaning the drip system by avoiding drippers clogging. Soil and water erosion are prevented.

1.2 Disadvantages and Potential Risks Fertigation can be an effective and safe method of applying certain chemicals to plants or to soil. However, a fertigation system cannot draw water from any water supply unless that source is protected from contamination. Disadvantages of fertigation under sprinkler and drip irrigation systems (Threadgill, 1991; Hoffman et al. 1992): Both the components (drip and water soluble fertilizer) are very costly. Maintenance of drip irrigation is difficult. There is possibility of theft and rat infestation. • • • • • •

Good-quality water is essential. Clogging of emitters may cause a serious problem. The availability of soluble types of fertilizers is limited. The adjustment of fertilizers to suit plant needs is not easy to perform. The risk of infestations of insects, pests and diseases increases. Due to a fear of yield loss because of the relatively lower dose of fertilizers in fertigation, farmers have a tendency to add additional fertilizers and irrigation water.

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1 Introduction to Chemigation and Fertigation

• Over fertilization, in case that irrigation is based on actual crop water requirements. • Unequal chemical distribution when the irrigation system design or operation is faulty. • Calibration to achieve the proper chemical injection rate is required for each chemigation system and for each irrigation system. • Leaching if rainfall occurs at the time of fertilizer application. • Chemical reactions in the irrigation system lead to corrosion, precipitation of chemical materials and clogging. • Potential non-targeted chemical application, which can occur as a result of drift, malfunctioning equipment such as end gun shutoffs, and runoff. • Potential excessive over-application or under-application of chemicals. • The calibrated injection rate may need to be changed during the application period especially for corner-pivot system and center-pivot gun turning On/Off periods. • Safety equipment malfunction during chemigation using continuous move irrigation system (i.e. centre pivot and liner move) may result in excessive overapplication or under-application of chemicals on a concentrated area (e.g. when the chemical injection system continues to operate after the irrigation water pump has shut down). • Fertigation must recognize that safe and effective chemigation requires careful and attentive management. Potential risks The greatest risk caused by fertigation is the potential for accidental backflow of a chemical into the irrigation water source. In order to prevent contamination, an irrigation system along with anti-pollution safety devices must be properly installed, operated and maintained. There are three primary ways that irrigation water sources can be polluted. They are: 1) chemicals in the supply tank, 2) in the irrigation pipeline, and 3) chemical backflows or siphoned into the water source when the irrigation system shuts down. The irrigation system shuts down, but the fertigation system continues to inject the chemical into the irrigation water supply. With a loss of system pressure or with a reduction in water flow sufficient to adversely affect the application rate, the system interlock must discontinue the product injection. Fertigation should not be performed under the following conditions: • The injection of a pesticide or fertilizer into an irrigation system on the suction side of the irrigation pump. • The direct connection of an irrigation system to a public water system.

1.3 Factors Affecting Chemigation and Fertigation

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1.3 Factors Affecting Chemigation and Fertigation 1.3.1 Irrigation System Characteristics The physical characteristics of an irrigation system can affect the capacity to applying agricultural chemicals (i.e. fertilizers, herbicides or pesticides). Most irrigation systems can be used to apply fertilizers or pesticides that must be incorporated into soil. However, only a sprinkler system can be used where foliar application is required. Any system used to apply fertilizers must have the appropriate injection equipment and anti-pollution safety devices installed, and the entire system must be in good working order. The preferred method is to use a differential pressure tank or venturi under drip irrigation and to use electric dosing pumps and piston pumps in the other systems. In the sprinkler irrigation system, especially the centre pivot, safety devices are required. If appropriate safety equipment is not installed to maintain the injection of chemicals and irrigation equipment, there is a possibility that the water supply will become contaminated. If no safety equipment is present, three specific problems may occur: 1.

2.

3.

The sudden and unexpected turn off of the irrigation pumping station due to mechanical or electrical failure, may cause an intensive chemical or a mixture of chemical and water to backflow into the water supply. The shutdown of the irrigation pumping station while continuing to carry out the injection equipment will cause a high concentration of unwanted chemicals in the irrigation pipeline. It may also cause the clogging of drippers, mini- and micro-sprinklers, micro-sprays and jets. The stop of injecting chemicals while continuing to pump irrigation water, may cause a backflow through the supply tank and chemical exceeded will be dispensed on the ground.

To reduce the potential problems that may occur, the following steps must be taken: Irrigation pipeline check valve: A check valve must be installed in the irrigation pipeline between the irrigation pump and the point of chemical injection into the irrigation pipeline in order to prevent water and chemicals from draining or siphoning into the water source. Vacuum relief valve: The vacuum relief valve is used to prevent the gravity flow of the chemical supply tank into the irrigation pipes,and to prevent the opposite flow of the irrigation system water into the chemical supply tank causing overflow. The vacuum relief valve must be located on top of the irrigation pipeline between the irrigation pump and the irrigation pipeline check valve in order to prevent a vacuum that could cause siphoning when the water flow stops, and to get rid of air in the main line at the start of the operation system. The diameter of the vacuum relief valve should be at least 1.9 cm (3/4 ).

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1 Introduction to Chemigation and Fertigation

Fig. 1.1 Schematic drawing of typical irrigation pipeline check valve

Inspection port: In most cases, the vacuum relief valve also serves as an inspection port. It is provided to check for malfunctions in the irrigation pipeline check valve and low pressure drain. It must be sited between the irrigation pump and the irrigation pipeline check valve so that the inlet to the low pressure drain can be observed (see Fig. 1.1). A minimum 10.16 cm (4 ) diameter opening is required for the inspection port. Chemical injection line check valve: The check valve should be installed in the chemical injection line between the chemical injection pump and the chemical injection port of chemicals on irrigation pipeline in order to: prevent the flow of dangerous chemicals from the supply tank in the line of irrigation pipes; and prevent the flow of water from the irrigation system into the chemical supply tank, causing a flood. The following safety measures should be implemented when using fertigation: • The presence of a fresh water source close to the supply tank and chemical injection pump for washing is required. • It is necessary to avoid any direct contact between chemicals and the skin. • It is essential to fix a fresh water outlet between the line of irrigation and the water supply pipes check valve, and it should not be used as a source of drinking water. • To reduce the hazard of damage to the skin, it is advisable to wear gloves and a face protection mask when performing chemical dilutions.

1.3 Factors Affecting Chemigation and Fertigation

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• Chemicals must be added to the water, not the other way round, in the preparation of dilutions in the chemical tank. • To avoid clogging the injection pump, the check valve or other equipment, a strainer between the chemical supply tank and the other equipment must be installed. The strainer should be checked before every use. • Adequate distance must be considered between chemical supply and mixing tanks, injection pumps, etc..., In case of using electric energy, any electrical cables might produce arcs or sparks to avoid explosion or fire hazards. Also all electrical cables in control head room must be sealed • The slope of the earth surface around the water source should facilitate runoff far away rather than towards it. • Anti-chemical corrosive and interaction materials and equipment must be used in order to provide an acceptable level of operator safety as well as to protect against contamination of the irrigation water source. 1.3.1.1

Distribution Uniformity (DU)

Due to the limited quantity of water resources, the efficient and equitable use of water is of paramount importance in Egypt. Therefore, a sustainable demand-led approach, focusing on the achievement of more efficient irrigation and fertigation practices, is one of the most viable options in water management and conservation techniques. This can only be achieved through effective design, maintenance and of irrigation systems. The uniformity with which an irrigation system applies water has an effect on the efficiency of the system. The uniformity of an irrigation system needs to be high to ensure that the majority of the crop receives an adequate amount of water. This is required in order to produce high yields and to have minimal nutrient loss at the field level. In this regard, the distribution uniformity of irrigation water is of great importance to modern irrigation systems, especially in countries with arid and semi-arid conditions where irrigated agriculture is mainly practised. There is a direct correlation between the distribution uniformity of irrigation systems and the distribution of fertilizers under fertigation practices. By achieving a more efficient distribution uniformity of water, a highly efficient distribution uniformity of fertilizer for plants is granted, consequently achieving a fair distribution of water and fertilizer for all plants under the irrigation system and thus increasing the efficiency per unit of water and fertilizer. The common uniformity measures for sprinkler and micro-irrigation systems are described as follows: 1.

Christiansen’s uniformity coefficient (Cu):

This is commonly used to describe the uniformity for stationary sprinkler irrigation systems and can be expressed as: 

1 − |Xi − X m| Cu = 100  Xi



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1 Introduction to Chemigation and Fertigation

where Cu Xi

Christiansen’s uniformity coefficient (%). measured depth/volume of water in equally spaced cash cans on a grid arrangement (mm or ml). mean measured depth/volume of water in all cash cans (mm or ml).

Xm 2.

Adjusted uniformity coefficient (Cadj ) for the centre pivot:

Heermann and Hein (1968) revised the Cu formula to reflect the weighted area, particularly that intended for a centre pivot sprinkler, as follows:  Cad j = 100 1 −



  i Si 

  Si V i − V  Si (V i Si )

where Si Vi

the distance (m) from the pivot to the ith equally spaced catch container. the volume of water in the catch can in the ith container (mm or ml).

3.

Emission Uniformity (Eu):

For micro-irrigation systems, both the Cu and Cadj concepts are impractical because the entire soil surface is not wetted. Keller and Karmeli (1975) developed an equation for micro-irrigation design as follows: 

Eu = 100 1 − 1.27(Cvm)n

−( 21 )

qmin  qx

where Eu Cvm n qmin qx 4.

the design emission uniformity (%) the manufacturer’s coefficient of variability in the emission device flow rate. the number of emitters per plant the minimum emission device flow rate (1/h) at the minimum system pressure the mean emission device flow rate (1/h). Coefficient of design uniformity (Cud):

This is based on emitter discharge rate deviation from the average rate, which is given as:  1 Cud = 100 1 − 0.798(Cvm)n −( 2 ) where Cud Cvm

the coefficient of design uniformity (%) the manufacturer’s coefficient of variability in the emission device flow rate

1.3 Factors Affecting Chemigation and Fertigation

n 5.

9

the number of emitters per plant. Low-quarter distribution uniformity (Du):

This is commonly used for surface irrigation systems, but it can also be applied for micro-irrigation and sprinkler irrigation systems. The general form of the distribution uniformity (Merriam and Keller 1978) can be given as:  Du = 100

Dlq Dav



where Du Dlq Dav

distribution uniformity (%). the average depth of water infiltrated/received in the low one-quarter of the field (mm). the average depth of water infiltrated/received over the field (mm).

1.3.2 Soil Characteristics Soil texture and structure, soil depth and profiles, and drainage are considered to be the main factors that affect farm irrigation systems and the selection of fertigation techniques. These main factors in addition to soil salinity affect through their effect on the available soil moisture (field capacity, the permanent wilting point and the infiltration rate of the soils). The available soil moisture affects the frequency of irrigation and therefore the application rates from sprinkler and localized irrigation systems should be studied carefully. Generally, coarse-textured soils have high intake rates and low soil moisture storage capacities. They also require more frequent applications of water. Light soils favour the adoption of sprinklers or localized irrigation. Pore space and particle size play a major role in the movement of water through the soil. Sandy soils have typically elongated and narrow wetted patterns around each emitter. Movement downwards is significantly greater than upwards or sideways. Clay soils typically have ‘squatter’ wetted areas around each emitter, with shallower but broader patterns than sands (see Fig. 1.2). Soils can differ considerably over relatively short distances. Several different soil textures are commonly found within a single field. The rate at which water and/or agricultural chemical(s) enters the soil (the infiltration rate) differs according to the soil texture. For example, coarsetextured sandy soils have high infiltration rates. Assuming that all other factors are equal (e.g. slope or compaction), there is less potential for runoff in coarse-textured soils than in fine-textured silty or clayey soils that have greater infiltration rates. In coarse-textured sandy soils, chemigating with excessive amounts of irrigation water could result in leaching the chemical below the crop root zone, whereas the situation is reversed in fine-textured, clayey soils that are to be chemigated. The potential for the deep percolation of water and/or chemicals is decreased, but the potential for runoff increases.

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1 Introduction to Chemigation and Fertigation

Fig. 1.2 The effect of soil texture on the wetted area around emitters

1.3.3 Topography The topography of the field can substantially affect the uniformity of water application through sprinkler irrigation systems that lack sprinklers with pressure regulators. Differences in elevation along the length of the sprinkler system will cause differences in pressure at each nozzle outlet. This results in uneven water distribution, especially in low-pressure systems. Uneven water distribution can be corrected by using pressure regulators on each individual sprinkler or sprinkler line. If distribution variances are not corrected, the irrigation system may be unsuitable for fertigation. In the case of drip irrigation, drippers should be located in parallel to contour lines from the slopes whenever possible. If the surface runoff happens with greater than 3% gradient areas, it must be considered to drip from the top to the bottom of the slope line density. The drip line should be placed at the head of two-thirds of the slope at the recommended spacing for the type of soil and plant material in use. For areas exceeding 3% in elevation change, less than one-third of the sloped area is separated from the upper two-thirds. In the case of sprinkler irrigation, a lower flow rate of water than the infiltration rate of the soil should be used so as not to cause runoff.

References Arnaout MA (1999) Comparative study between fertigation and conventional methods of fertilizer application through different irrigation systems. Miser J Ag Eng 16(2):209–217 Arora I, Singh CP, Lal S (2015) Fertigation in vegetables crops. Am Int J Res Form Appl Nat Sci 10(1):14–17 Bar-Yosef B (1991) Fertilization under drip irrigation. In: Palgrave DA (ed) Fluid fertilizer, science and technology. Chafer Fertilizer Britag Industries Ltd., Chedburgh, Suffolk. Marcel Dekker, Inc., New York Hagin J, Sneh M, Lowengart-Aycicegi A (2002) Fertigation—fertilization through irrigation. In: Johnston AE (ed) IPI Research Topics No. 23. International Potash Institute, Basel Heermann DF, Hein PR (1968) Performance characteristics of self-propelled centerpivot sprinkler irrigation system. Trans ASAE 11:0011–0015. https://doi.org/10.13031/2013.39320

References

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Hoffman GJ, Howell TA, Solomon KH (1992) Management of farm irrigation system. ASAE Monograph No. 9 ASAE, USA, p 1040 Keller J, Karmeli D (1975) Trickle irrigation design. Rainbird Sprinkler Manufacturing, Glendora, CA, p 133 Merriam JL, Keller J (1978) Farm irrigation system evaluation: a guide for management. Department of Agriculture and irrigation Engineering, Utah Stat University, Loban Threadgill ED (1991) Advances in irrigation, fertigation, and chemigation. Fertigation/Chemigation, Proc. Expert Cons. Fert./Chem., FAO AGL/MISC 19/91. Rome, Italy

Chapter 2

Selecting an Injector for Fertilizer/Chemical Injection

Abstract There are a wide range of fertilizer injectors, from the traditional simple tank to the automatic injector, used in fertigation system. Several techniques have been developed for applying fertilizers through irrigation systems and many types of injectors are available on the market. This chapter describes the methods to be used when selecting an injector for efficient fertilizer/chemical injection and the equipment required to apply chemicals through an irrigation system. Different types of injectors used at the field level, their advantages and disadvantages, details of the injector, and methods of operation are presented. Frequent maintenance and calibration to ensure optimal injector performance and the production of healthy crops are discussed. Keywords Fertilizer injectors · Chemical supply tank · Venturi · Piston pump · Hydraulic energy · Diaphragm pumps and electric dosing pumps

2.1 Fertigation Injectors Fertigation injectors are devices used to apply water-soluble fertilizers, pesticides, plant growth regulators, wetting agents and mineral acids during crop production. The injectors represent a vital part of modern irrigation systems and are used as an easy time-saving and labour-saving method of applying liquid chemical solutions to the cultivated crops. There are two main techniques for applying chemicals through irrigation systems: the ordinary closed tank and the injector pump. Both systems are operated by the system’s water pressure. The injector pumps are mainly either Venturi-type or piston pumps. The closed tanks are always installed on a bypass line, while the piston pumps can be installed either in-line or on a bypass line. These types are mechanically durable, reliable and accurate chemical injection systems specifically designed to be used for fertigation. Like other mechanical devices, proper and frequent maintenance and calibration are crucial steps that need to be taken in order to ensure optimal injector performance and the production of healthy crops.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 A. M. Taha, Fertigation: A Pathway to Sustainable Food Production, SpringerBriefs in Environmental Science, https://doi.org/10.1007/978-3-031-05596-6_2

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2.2 The Chemical Supply Tank The chemical supply fertilizer (closed) tank is a cylindrical, epoxy-coated and pressurized metal tank that is resistant to the irrigation system’s pressure and is connected as a bypass to the supply pipe of the head control. It operates by differential pressure created by a partially closed valve, placed on the pipeline between the inlet and the outlet of the tank. Part of the flow is diverted to the tank entering at the bottom and is mixed with the fertilizer solution; the dilution is then ejected into the system. The dilution ratio and the rate of injection are not constant. One disadvantage of this tank is that the concentration of fertilizer is high at the beginning and very low at the end of the operation. This apparatus is still in service on a large scale in some small farms in the newly reclaimed sandy soils in Egypt because of its low cost and the ease of its manufacture (see Figs. 2.1 and 2.2). The mineral fertilizers used in these fields are applied through the differential pressure tank of different capacities, e.g. 100, 150,

Fig. 2.1 The chemical supply tank

2.2 The Chemical Supply Tank

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Fig. 2.2 Injected concentration over time using a chemical supply tank

200, 250 and 300 L. The tank is connected to the irrigation line by a hose (20 mm in diameter) through two inlet and outlet valves. In order to avoid potential reactions with chemicals placed in it, the chemical supply tank should be constructed of a corrosion-resistant material such as stainless steel or sunlight-resistant plastic. The tank should be designed to prevent any wind-borne foreign materials—for example, dirt, leaves or crop residue—and rainwater from getting into the tank. It should also be completely drainable with a sump at the drain port for ease of rinsing. Accurate, easily readable gallon marks should appear on the outside of the tank. In the case of applying pesticides, labels including statements that the product should only be placed in a specific type of tank should be added. Product labels also should include a warning if chemical interaction could lead to potential problems for humans. Agitation in the chemical tank is required with some pesticides (tank mixes, dry, wettable powders, or any other suspended formulations). Hydraulic agitation may be sufficient for some soluble chemicals, while mechanical agitation may be necessary for other types of chemicals. In addition, there should be a reference to the product label for specific instructions. Advantages: • It is affordable and familiar to many Egyptian farmers. • It is easy to use and maintain. Disadvantages: • It is important that the injection rate is monitored, due to the decreasing concentration of the solution over the course of the fertigation period. • It had limited capacity. • There is a danger of suction air entering the system unless all fittings are airtight. • There is a risk of contamination of the water supply if chemicals flow back. • Generally, it can only supply a single fertilizer at a time and requires manual operation.

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2.3 Venturi This type of fertilizer injector (see Figs. 2.3 and 2.4) is based on the principle of the Venturi tube. A pressure difference is required between the inlet and the outlet of the injector. It is installed on a bypass arrangement placed on an open container with the fertilizer solution. The rate of injection is very sensitive to pressure variations, and small pressure regulators are sometimes needed for a constant ejection. Friction losses are approximately 1.0 atm. The injectors are made of plastic in sizes ranging from 1.9 cm (≈3 /4 in.) to 5.0 cm (≈2.00 in.) and with injection rates of 40–2000 L/hr. They are relatively cheap compared to other injectors. As water passes through the throat of the meter, pressure energy is converted into velocity energy. In the process, a nearly perfect vacuum is developed at the throat. The vacuum creates a pressure differential that causes the chemical to be forced out of the chemical supply tank into the bypass line. The chemical injection rate is varied by using a needle valve or orifice plate placed in line between the chemical supply tank and the meter. Systems with large pipelines place the venturi in a shunt or bypass line arrangement. To ensure that the pressure in the bypass line is greater than the mainline pressure, a booster pump is installed in the bypass line. This eliminates the need to artificially create a pressure differential by installing a throttling valve in the mainline. Therefore, it does not favour the use of the venturi in sprinkler irrigation systems because it causes significant loss of pressure during the fertilization process through irrigation water, and thus reduces the efficiency of water and fertilizer distribution uniformity. Using the venturi injector in the drip irrigation system on a small farm level achieves good results in the conditions prevalent in Egypt. Advantages: • It is typically manufactured from plastic and does not have any moving parts. • It requires little maintenance. • Gate valves control fertilizer injection rates with some accuracy (fertilizer concentration is constant throughout the injection time). • Large volumes can be mixed and stored on site. • It is inexpensive and more convenient for Egyptian farmers. • It is easy to use and gives a fixed concentration over time. Disadvantages: • It requires a closed pipe system. • Pressure loss occurs in the main irrigation line (which can be up to 33%) within the network, so while it is suitable for drip irrigation, it is not suitable for sprinkler irrigation.

2.3 Venturi

Fig. 2.3 Venturi injector

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Fig. 2.4 Injected concentration over time using a venturi injector

2.4 Piston Pumps This type of injector (see Figs. 2.5 and 2.6) is powered by the water pressure of the system and can be installed directly on the supply line and not on the bypass line. The system’s flow activates the pistons and the injector is operated, ejecting the fertilizer solution from a container, while maintaining a constant rate of injection. The rate varies from 9 to 250 L/hr, depending on the pressure of the system, and it can be adjusted by small regulators. This type of injector is made of durable plastic material and is available in various models and sizes. These are more expensive than the Venturi-type injector. The fertilizer solution in liquid form is fed into the system at low rates repeatedly, on a continuous basis, during irrigation. The flow rate of the injector should be such that the calculated amount of solution is supplied at a constant rate during the irrigation cycle, i.e. starting fertigation immediately after the system starts operating and finishing a few minutes before the operation ends. In the

Fig. 2.5 The piston pump

2.5 The Hydraulic Piston Motor Injector (Hydraulic Energy)

19

Fig. 2.6 Injected concentrations over time using a piston pump

conditions prevalent in Egypt, this type of injector is not favoured by farmers since it has highly priced spare parts and maintenance costs. Advantages: • It has a high discharge rate—up to 250 L/hr—that makes it suitable for large areas. • It can be operated manually or automatically by an irrigation controller manual operation. • It has a constant fertilization rate, which can be used to apply precise amounts of fertilizer. Disadvantages: • It has highly priced spare parts and maintenance costs. • Chemicals or fertilizers come into direct contact with the piston and seat, resulting in excessive wear and potential leakage into the environment. • Moving parts, such as motor to gearbox coupling, the eccentric arm the and plunger arm, are generally exposed, creating dangers for the operator and others.

2.5 The Hydraulic Piston Motor Injector (Hydraulic Energy) This type of injector is powered by a linear hydraulic motor piston from the hydraulic pressure generated in the irrigation system and does not require any other source of energy for the injection of fertilizers into the pressurized irrigation line. Water enters the injector through the inlet upstream and heads out to the drain line through the water outlet. The liquid fertilizer enters the injector through the suction port positioned inside the fertilizer tank and is injected through the injection outlet, downstream, into the irrigation line. The fertilizer is injected at twice the pressure of the irrigation line. Water consumption of the hydraulic motor is three times the quantity of the chemical

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2 Selecting an Injector for Fertilizer/Chemical Injection

injected and it can produce an injection flow rate of up to 320 L/hr, depending on the inlet pressure and the pump model (see Fig. 2.7). Advantages: • It has a high discharge rate—up to 320 L/hr—which makes it suitable for large areas. • It can be operated manually or automatically by an irrigation controller manual operation. Disadvantages: • It requires a certain level of maintenance. • The selected pump must be stainless steel and/or have a bronze impellor. • It contains a large number of working components and many moving parts.

Fig. 2.7 The hydraulic piston motor injector: a piston pump—suction stroke; b piston pump— discharge stroke; c double acting piston pump

2.6 Diaphragm Pumps

21

• The pumps are sensitive to air pockets and need a continuous water discharge in order to operate the piston or diaphragm. • The spent ‘drive water’ is lost and discharged from the system.

2.6 Diaphragm Pumps Diaphragm pumps (see Fig. 2.8) have a membrane or diaphragm separating the drive mechanism from the product being pumped. The mode of action is that of a positive displacement pump, but the chemical being pumped is not in direct contact with the piston. Water pumped into the lower chamber activates a rubber diaphragm in the drive unit which forces the diaphragm up, and in doing so forces the fertilizer out of the injector into the irrigation system via a drive rod. On the return stroke, the spent drive water is discharged from the lower chamber of the drive unit while the fertilizer solution is drawn into the injector (see Fig. 2.9). The cycle is automatically repeated. Injection rates ranging from 3 to 1,200 L per hour are possible. The chemical to be injected determines the diaphragm material that is selected. Selecting an appropriate pump diaphragm will eliminate leakage problems that are associated with piston pumps. Diaphragm pump also automatically stops. This is perfect equipment for accurate fertigation. Advantages: • • • • • • •

It is simple and effective. It is relatively easy to install. There is no pressure loss in the main irrigation line Automation is relatively easy. Operation costs are low. It is easy to calibrate simply by turning an adjustment dial. It is easy to achieve precise injection rates due to fine gradations on the dial.

Fig. 2.8 The diaphragm pump

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2 Selecting an Injector for Fertilizer/Chemical Injection

Fig. 2.9 Cross-section drawing of the pump mechanism for a diaphragm-type chemical injection pump (Poynton 1983)

• It is easy to adjust injection rates because the system does not need to be shut off for adjustment. Disadvantages: • • • • • •

Pumps must develop a minimum mainline pressure in order to operate. An electric power source is potentially required in order to operate. It requires a certain level of maintenance. The selected pump must be made of stainless steel and/or have a bronze impellor. It has a large number of working components. The pumps are sensitive to air pockets and need continuous water discharge in order to operate the piston or diaphragm. • The spent ‘drive water’ is lost and discharged from the system.

2.7 Electric Dosing Pumps

23

2.7 Electric Dosing Pumps Electric pumps (see Figs. 2.10 and 2.11) are those in which all parts are made from stainless or rubber so as not to react with chemicals. These pumps often have high performance and fit center pivot system. The pump flow rate is up to 25 L/hr. It is normally used for the injection of chemicals and acids for system maintenance. The pump maximum pressure is 10 bars (145 psi). The flowing rate of the irrigation system should be considered when a certain fertigation concentration to be injected, and it is also necessary to install a back flow safety valve in order to protect the water source from chemical pollution. Electric pumps can be helpful in controlling the injection rate and the concentration during irrigation time.

Fig. 2.10 Types of electric dosing pumps

24

2 Selecting an Injector for Fertilizer/Chemical Injection

Fig. 2.11 Injected concentrations over time using electric dosing pumps

Reference Poynton JP (1983) Metering pumps: selection and application (chemical industry). Mercel Dekker Inc., p 212

Chapter 3

Fertilizers for Fertigation

Abstract This chapter discusses the types of fertilizers that are suitable and compatible for fertigation, and types of water-soluble fertilizers. Insoluble fertilizers, due to their chemical properties or manufacturing methods, are generally not suitable for use in fertigation systems because of the amount of impurities present. Soluble solid and liquid fertilizers are both suitable for fertigation depending on their availability, profitability and convenience. In terms of being suitable for fertigation, the properties of fertilizers depend on the methods of their manufacture, the quality of materials used in the manufacturing industry and their suitability for the fertigation process. The chemical properties that should be followed to determine the solubility of certain fertilizers are acidity, quantity, corrosion and compatibility. The process of selecting a fertilizer that is suitable for a specific application should be based on several factors: nutrient form, purity, solubility and cost. Keywords Forms of fertilizers · Chemical characteristics of fertilizers · Types of water-soluble fertilizers · Suitability of fertilizers · Compatibility of fertilizers The selection of fertilizers that are suitable for a specific application should be based on several factors, including nutrient form, purity, solubility and cost.

3.1 Forms of Fertilizers Both soluble solid and liquid fertilizers are suitable for fertigation, depending on their availability, profitability and convenience. Some commercial agricultural fertilizers are generally not suitable for use in fertigation systems due to the presence of insoluble amounts of impurities, which lead to dripper clogging. In order to avoid this problem, grade salts (e.g. potassium sulphate), acids (e.g. nitric acid), bases (e.g. potassium hydroxide), polymers (e.g. polyphosphate) or chelates (e.g. iron EDTA) are injected into the irrigation water as solutions (i.e. pre-dissolved in water). These fertilizers are used in fertigation systems because they contain fewer impurities and

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 A. M. Taha, Fertigation: A Pathway to Sustainable Food Production, SpringerBriefs in Environmental Science, https://doi.org/10.1007/978-3-031-05596-6_3

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26

3 Fertilizers for Fertigation

proportionally higher levels of the necessary mineral nutrients. Several fertilizers can be injected into the pressurized irrigation systems. Soluble NPK fertilizers that are appropriate for use in fertigation are available on the market, but their price might be a major constraint. The main nitrogen fertilizer sources for fertigation include the following: – Ammonium nitrate (20-0-0). NH4 NO3 -H2 O is ammonium nitrate fertilizer dissolved in water. – Urea-ammonium nitrate (32-0-0). (NH2 )2 2CO-NH4 NO3 . Urea-ammonium nitrate solution is manufactured by combining urea (46% N) and ammonium nitrate (35% N) on an equal nitrogen content basis. – Calcium nitrate (15.5-0-0-19Ca). 5Ca(NO3 )2 -NH4 NO3 -10H2 O. This fertilizer is high in nitrate-nitrogen (14.5%) with 1% ammonium-nitrogen and supplies calcium. – Ammonium thiosulphate (12-0-0-26). (NH4 )2 S2 O3 is used as both a fertilizer and as an acidulating agent. When applied to the soil, Thiobacillus bacteria oxidize the free sulphur into sulphuric acid. Potassium fertilizers can be supplied in the following forms: – Potassium chloride (0-0-62). Potassium chloride (KCl) is generally the leastexpensive source of potassium and is the most popular K fertilizer applied through fertigation. – Potassium sulphate (0-0-52). K2 SO4 can be an alternative to KCl in high salinity areas and provides a source of sulphur, – Potassium thiosulphate (0-0-25-17 and 0-0-22-23). K2 S2 O3 (KTS) is marketed in two grades and is a neutral to basic, chloride-free, clear liquid solution. – Potassium nitrate (13-0-46). Potassium nitrate is expensive, but growers who use it benefit from both the nitrogen and the potassium in the product. Potassium nitrate is considered to be the preferable form used in fertigation. If salinity is a problem, potassium chloride and potassium sulphate should not be used. As for phosphorus fertilizers, the selection of favourable form is more limited, since single-, double- and triple-strength superphosphate and rock phosphate are unsuitable for use in fertigation systems. Liquid phosphorus fertilizers, except for good-brand phosphoric acid, may contain impurities that complicate efforts to eliminate chemical precipitation in the drip lines. Good-brand phosphoric acid and ammonium phosphate solutions can be used successfully if sufficient knowledge is possessed and sufficient attention is paid during applications. The most commonly used phosphorus fertilizers are urea phosphate or ammonium phosphate solutions, while monoammonium and monopotassium phosphate are also available for use. The insoluble sources of calcium (Ca) such as gypsum, which is mostly used to help remove excessive contents of sodium ions (Na+ ) from the soil profile and improve soil structure, can also be introduced into the irrigation water. However, in order to prevent dripper clogging, it must be very finely ground and the source tank should be constantly agitated to prevent the settling of fine particles. In the case

3.2 Suitability of Fertilizers

27

of mixing fertilizers, the reaction between anions from one fertilizer and cations from another fertilizer should be considered in order to avoid the formation of an insoluble precipitate and clogging problems in the irrigation system—for example, the use of calcium (Ca2+ ), which forms insoluble precipitates with phosphate (PO4 3– ) or sulphate (SO4 2– ). Therefore, the compatibility of different fertilizers must be considered.

3.2 Suitability of Fertilizers In fertigation practice, all fertilizer sources must be highly soluble. However, not all fertilizers are suitable for fertigation, as some are insoluble due to their chemical properties or manufacture. A wide range of fertilizers, in both solid and liquid forms, are suitable for fertigation depending on the physical and chemical properties of the fertilizer solution. For large-scale field operations, solid fertilizer sources are a less expensive option compared to the commonly used liquid fertilizers. The solubility of these fertilizers varies considerably. When using a solid fertilizer source, sufficient quantities of water should be added to the stock solution in order to avoid any possible problems. Chemical reactions between fertilizer materials can result in the formation of precipitates, which can block the irrigation system. The uniformity of the fertilizer application depends on the uniformity of the applied water by the irrigation system. Therefore, high water application uniformity is very important for the achievement of a highly efficient fertigation process. Fertilizers used for the purpose of fertigation should be chosen by considering two main points: (1) solubility; and (2) the degree of acidity of the fertilizer solution in relation to its corrosiveness to the irrigation system components.

3.2.1 Solubility Solubility is defined as the amount of a fertilizer dissolved in a specific amount of water. If the maximum solubility of certain fertilizer is exceeded, the fertilizer will precipitate in the injection tank and plants will not receive the full dose. In addition, undissolved fertilizer can clog irrigation tubing and drip emitters. Therefore, high and complete solubility is essential for fertilizers used in fertigation. The following guidelines should be followed when determining the solubility of certain fertilizers: (1) (2) (3)

All ammonium, nitrate, potassium, sodium and chloride salts are soluble. All oxides, hydroxides and carbonates are insoluble. All sulphates are soluble except for calcium sulphate.

Fertilizer solubility is generally affected by the pH of the growing medium, the chemical form of the nutrient, and the temperature (see Table 3.1).

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3 Fertilizers for Fertigation

Table 3.1 The effect of chemical form, soil pH and temperature on the solubility rates of fertilizers Fertilizer

N-P2 O5 -K2 O Chemical formulae

Other Soil nutrients pH

Solubility (g/100ml water) 0 °C

10 °C

20 °C

30 °C

Nitrogen fertilizers Ammonium nitrate

34-0-0

NH4 NO3

–

Ammonium polysulphide

20-0-0

NH4 Sx

–

Ammonium sulphate

21-0-0

(NH4 )2 SO4

24% S

Ammonium thiosulphate

12-0-0

(NH4 )2 S2 O3

–

Acidic

Acidic

118 152 192

242

–

–

High

–

71

73

75

78

–

–

Very high

–

Calcium nitrate

15.5-0-0

Ca(NO3 )2 .4H2 O

17% Ca

Basic

102 112 121

150

Urea

46-0-0

CO(NH2 )2

–

Acidic

–

78

–

–

Urea sulphuric acid

28-0-0

CO(NH2 )2 .9H2 SO4

–

–

–

High

–

Urea ammonium nitrate

32-0-0

CO(NH2 )2 .NH4 NO3

–

–

–

High

–

Phosphorus fertilizers Ammonium phosphate

11-48-0

NH4 H2 PO4

1.4% Ca Acidic and 2.6% S

23

29

37

46

Ammonium polyphosphate

10-34-0

(NH4 )5 P3 O10 and others

–

–

–

High

-

Ammonium polyphosphate

16-37-0

(NH4 )7 P5 O16 and others

–

High

-

Phosphoric acid, green

0-52-0

H3 PO4

–

548 –

–

-

Phosphoric acid, white

0-54-0

H3 PO4

–

–

–

45.7

-

Very acidic

Potassium fertilizers Potassium chloride

0-0-60

KCl

–

Neutral –

–

34.7

-

Potassium nitrate

13-0-44

KNO3

–

Basic

21

31

45

Potassium sulphate

0-0-53

K2 SO4

8% S

Neutral 7

9

11

13

Potassium thiosulphate

0-0-25-17S

K2 S2 O3

–

–

–

150

–

13

(continued)

3.2 Suitability of Fertilizers

29

Table 3.1 (continued) Fertilizer

N-P2 O5 -K2 O Chemical formulae

Monopotassium 0-52-34 phosphate

KH2 PO4

Other Soil nutrients pH

–

Basic

Solubility (g/100ml water) 0 °C

10 °C

20 °C

30 °C

–

–

33

–

Micronutrient fertilizers Borax

11% B

N2 B4 O7

–

–

–

2.1

–

Boric acid

17.5% B

H3 BO3

–

–

–

6.35

–

Solubor

20% B

Na2 B8O13

–

–

–

22

–

Copper sulphate (acidified)

25% Cu

CuSO4

–

–

–

31.6

–

CuCl2

–

–

–

71

–

Cupric chloride (acidified) Gypsum

23% Ca

CaSO4

–

–

–

0.241 –

Iron sulphate (acidified)

20% Fe

FeSO4

–

–

–

15.65 –

Magnesium sulphate

9.67% Mg

MgSO4 ·7H2 O

–

–

–

71

Manganese sulphate (acidified)

27% Mn

MnSO4 ·4H2 O

–

–

–

105.3 –

Ammonium molybdate

54% Mo

(NH4 )6 Mo7 O24 ·4H2 O –

–

–

43

–

Sodium molybdate

39% Mo

Na2 MoO4

–

–

–

–

–

–

Zinc sulphate

36% Zn

ZnSO4 ·7H2 O

–

–

–

96.5

–

Zinc chelate

5–14% Zn

DTPA and EDDHA

–

–

–

Very high

–

Manganese chelate

5–12% Mn

DTPA and EDDHA

–

–

–

Very high

–

Iron chelate

4–14% Fe

DTPA and EDDHA

–

–

–

Very high

–

Copper chelate

5–14% Cu

DTPA and EDTA

–

–

–

Very high

–

Sulphuric acid

95%

H2 SO4

–

–

–

Very high

–

The effect of pH of the growing medium on the nutrient’s availability: The availability of several nutrients at pH values of 5, 6 and 7 are given as: nitrogen (High, High, High), phosphorus (High, Medium, Low), potassium (High, High, High), calcium (Low, Medium, High), magnesium (Low-Medium, Medium, High), iron chelate EDDHA (High, High, High), iron chelate EDHA (High, High, Low),

30

3 Fertilizers for Fertigation

iron sulphate (High, Medium, Low), manganese (High, Medium, Low), zinc (High, Medium, Medium), boron (High, Medium, Low) and molybdenum (Low, Medium, High). At a low pH (5.0–6.0), the iron, manganese, zinc and boron micronutrients are highly soluble and are easily taken up by the roots. At pH values that are too low (75% of the total roots in the top 60 cm soil depth were found at 0– 15 cm and