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FERTILIZER SULFUR AND FOOD PRODUCTION
Fertilizer sulfur and food production
by
l.S. KANWAR ICRISAT Hyderabad India
M.S. MUDAHAR IFDC Muscle Shoals, Alabama USA
1986 MARTIN US NIJHOFF lOR W. JUNK PUBLISHERS 111... a member of the KLUWER ACADEMIC PUBLISHERS GROUP DORDRECHT / BOSTON / LANCASTER "
Distributors
for the United States and Canada: Kluwer Academic Publishers, 190 Old Derby Street, Hingham, MA 02043, USA for the UK and Ireland: Kluwer Academic Publishers, MTP Press Limited, Falcon House, Queen Square, Lancaster LAI lRN, UK for all other countries: Kluwer Academic Publishers Group, Distribution Center, P.O. Box 322, 3300 AH Dordrecht, The Netherlands
Library of Congress Cataloging in Publication Data
Kanwar, Jaswant Singh, 1922-Fertilizer sulfur and food production.
"July 1985." Bibliography: p. 1. Sulphur fertilizers--Tropics. 2. Food supply-
Tropics. 3. Sulphur deficiency diseases in plants-Tropics. 4. Sulphur industry--Tropics. 5. Sulphur fertilizers--Research--Tropics. 6. Sulphur fertilizers-Government policy--Tropics. 7. Sulphur in nutrition. I. Mudahar, Mohindcr S. II. International Fertilizer Development Center. III. Title. S653.5.S84K36 1986 631.8'25 85-21614 ISBN-I3 978-94-010-8435-2 e-ISBN-I3 978-94-009-4352-0
DOl 10.1007/978-94-009-4352-0
Copyright
© 1986 by Martinus NijhofflDr W. Junk Publishers, Dordrecht. Softcover reprint of the hardcover 1st edition 1986
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publishers, Martinus NijhofflDr W. Junk Publishers, P.O. Box 163, 3300 AD Dordrecht, The Netherlands.
v
Table of Contents
List.of Tables ix List of Figures xiii Acronyms and Abbreviations xv Foreword xix Acknowledgments xxi
1 Introduction 1 Statement of the Problem 1 Objectives 3
2 Food and Nutrition Problems in Perspective 5 Population and Food Production 5 Magnitude and Location of Food Deficits 6 Malnutrition in Developing Countries 8 Sources of Calories and Protein Supply 11 Components of Food Production 12
3 Fertilizer Sulfur in Strategies for Food Production 15 Strategies for Expanding Food Production 15 Fertilizer in Agricultural Development 16 Importance of Sulfur 20 Sulfur in the Fertilizer Industry 22 The Sulfur Gap 25 Social Cost of Inadequate Sulfur Use 29 Economics of Fertilizer Sulfur 30
4 Sulfur in Plant, Animal, and Human Nutrition 33 Function of Sulfur in Plant Nutrition 33 Uptake and Translocation of Sulfur 33 Sulfur Uptake by Different Crops 35 Sulfur Application and Crop Quality 38 Sulfur Interactions With Other Nutrients 41
Sand N Interactions 41 Sand P Interactions 42 Sand K Interactions 44 Sand Ca, Mg Interactions 44 S and Micronutrient Interactions 44 Sand Mo Interactions 44 Sand Se Interactions 44
Uptake and Recovery of Applied Fertilizer Sulfur 45 Sulfur in Animal Nutrition 45 Sulfur in Human Nutrition 47
VI
5 Status, Diagnosis, and Determinants of Sulfur Deficiency 51 Sulfur Status of Soils in the Tropics 51
Delineation of Tropical Regions 51 Sulfur Status of Tropical Soils 53
Inorganic Sulfur 58 Sulfate Forms and Sources 58 Sulfates in Tropical Soils 61 Adsorbed Sulfates 62
Organic Sulfur 64 Ester Sulfates 64 Carbon-Bonded Sulfur Compounds 64 Transformation of Organic Sulfur 66
Diagnosis of Sulfur Deficiency 67 Soil Testing Methods 68 Soil Tests and Sulfur Response Correlation 70 Biological Methods 72 Tissue Testing for Sulfur Status 73
Determinants of Sulfur Deficiency 75 Soil Factors 75 Climatic Factors 77 Crops, Cropping Systems, and Crop Residue 79 Fertilizer Use and Management 83 Irrigation 86 Industrialization and Environmental Policies 89
Conclusions and Research Agenda 89
6 Crop Response to Fertilizer Sulfur in the Tropics 91 Asia 91
India 91 Bangladesh 98 Sri Lanka 99 Indonesia 99 Malaysia 100 Philippines 100 Thailand 100 Papua New Guinea 101 Summary for Asia 101
Africa 102 West Africa 102 East Africa and Southern Africa 106 Summary for Africa 110
Latin America 110 Brazil 111 Venezuela 113
VII
Costa Rica 113 Mexico 113 Colombia 115 Chile 115 West Indies 115 Ecuador 116 Nicaragua 116 Summary for Latin America 116
Residual Effects of Fertilization With Sulfur 116 Annual Crops 116 Perennial Crops 118
Conclusions and Research Agenda 118
7 Estimating Sulfur Requirements, Supplies, and Gaps 125 Determinants of Sulfur Uptake 125 Determinants of Sulfur Replacement Requirements 126 Model for Estimating Sulfur Requirements 126 Data for Estimating Sulfur Requirements 128 Estimated Aggregate Sulfur Requirements 130 Estimated Sulfur Requirements by Crops 134 Estimating Sulfur Requirements from Nitrogen and
Phosphorus Use 135 Trends in Fertilizer Sulfur Supply 138 Estimated Gaps in Sulfur Requirements and Sulfur Supply 142
8 Fertilizer Sulfur Sources and Supply Strategies 147 Sulfur Sources 147
Atmospheric Accession 147 Irrigation Water 147 Organic Material and Crop Residues 148 Fertilizers and Soil Amendments 148
Sulfur-Supplying Fertilizers and Soil Amendments 149 Considerations for Formulating a Sulfur Supply Strategy 149 Modification of Fertilizers to Supply Sulfur 154 Research on Sulfur Fertilizers 154
Modified Phosphate-Sulfur Fertilizers 155 Modified Nitrogen-Sulfur Fertilizers 155 Replenishing Sulfur Lost Through Leaching 155
Criteria for Evaluating Fertilizer Sulfur Sources 156
9 World Sulfur Situation, Outlook, and Public Policy 159 Sulfur Supply and Demand Components 159 Patterns and Trends in Sulfur Production 160 Patterns and Trends in Sulfur Consumption 161
VIII
Patterns and Trends in Sulfuric Acid Production Patterns and Trends in Sulfuric Acid Consumption Patterns and Determinants of World Trade in Sulfur Sulfur Trade Policies in Selected Countries Behavior of International Sulfur Prices Sulfur Reserves, Resources, and Their Use Production and Use of Phosphogypsum
164 168 172 176 177 180 186
10 Summary, Conclusions, and Recommendations 191 Sulfur - A Neglected Fertilizer Nutrient 191 Tropics and Food Production - The Target Area of Study 191 Sulfur in Plant Nutrition 192 Sulfur in Food Production and Human Nutrition 193 Sulfur Status in the Tropics - Additions 194
Sulfur-Supplying Capacity of Tropical Soils 194 Contribution of Sulfur From External Sources 195
Sulfur Status in the Tropics - Removals 196 Sulfur Balance Sheet and Likely Scenarios 200
Subsistence Agriculture 200 Modern Agriculture 200
Magnitude of Sulfur Deficiency in Tropical Soils 201 Determining Sulfur Deficiency in the Tropics 202 Crop Response to Fertilizer Sulfur 203 Priority Areas for Fertilizer Sulfur Research 205 Sulfur Strategies for Meeting the Challenge 205 Estimating Sulfur Requirements and Gaps 207 Evaluation of Alternative Fertilizer Sulfur Materials 211 Economic and Policy Analysis of Fertilizer Sulfur 213 Pricing of Fertilizer Sulfur 213 Sulfur Situation, Resources, Trade, and Outlook 214 Sulfur Trade Policies 216 Phosphogypsum: A Source of Fertilizer Sulfur 216 Need for Information Related to Fertilizer Sulfur 217 Fertilizer Sulfur Use Recommendations 217 Fertilizer Sulfur Regulation and Labeling 218 Sulfur, Environmental Protection, and Food Production 218 Implications for Research and Public Policy 219
Priorities for National Research Programs 219 Priorities for International Research Programs 220
References 223 Appendixes 241
IX
List of Tables
2.1 Regional Distribution of World Population and Food Production During 1981 6
2.2 Estimated Food Production, Consumption, and Deficits in Selected Countries and Regions of Developing Market Economies 9
2.3 Share and Magnitude of Population Considered Undernourished in Selected Countries and Regions of Developing Market Economies 10
2.4 Relative Contribution of Individual Food Items to Average Daily Per Capita Calorie Supply by Region and Economic Group, 1972-74 12
2.5 Relative Contribution of Individual Food Items to Average Daily Per Capita Protein Supply by Region and Economic Group, 1972-74 13
2.6 Relative Contribution of Individual Commodities to Food Production in Developing Market Economies During 1981 14
3.1 Level, Pattern, and Growth in Fertilizer Consumption for World Regions in 1981 18
3.2 Sulfur Removed by Selected Crops in Brazil 20 3.3 Average Sulfur Use and Loss in Manufacturing Selected
Fertilizer Products and Intermediates 24 3.4 Impact of Changing Technology on Average Annual Sulfur
Requirements in Tropical Agriculture: A Case of Wheat and Rice Cropping System 28
3.5 Average Response of Rice to Urea and Ammonium Sulfate in South Sulawesi, Indonesia 29
4.1 Sulfur Content of Various Plant Species 35 4.2 Estimated Nutrients (S and N, P, K) Removed by Different
Crops 36 4.3 Effect of Sulfur on Yield and Chemical Composition of
Groundnuts 40 4.4 Effect of Levels and Sources of Phosphorus on the Yield
and Sulfur and Phosphorus Concentrations in Groundnut Foliage 43
4.5 Fertilizer Sulfur Use Efficiency 46 4.6 Methionine and Crude Protein Content of Brown Rice
Treated With Urea or Ammonium Sulfate Grown in Ngale, East Java, Indonesia, 1974 Dry Season 47
4.7 Effect of Sulfur Fertilization on Protein: Total Essential Amino Acids and Sulfur-Containing Amino Acid Content of Cereals in India 48
X
5.1 Estimated Area of Major Soil Groups in the Humid Tropics 52 5.2 Estimated Area of Major Soil Groups in the Semiarid
Tropics 53 5.3 Total Sulfur Values for a Range of Soils From Tropical
Regions 54 5.4 Ratio of Sulfur to Other Nutrients in West African Soils 57 5.5 Sulfur Content in Some Nigerian Soils (On Dry-Matter
Basis) 58 5.6 Natural and Artificial Sources of Sulfur Generation on the
Earth 60 5.7 Mean Carbon:Nitrogen:Sulfur Ratios in Selected Soils in the
World 65 5.8 Critical Levels of Sulfur in Soil for Different Crops and in
Different Countries 69 5.9 The Effect of Liming and Leaching on Soil Sulfate, Total
Soil Sulfur, and the Amounts of Sulfate Leached 84 5.10 Changes in Soluble Sulfate in Soil at Various Depths and
Different Periods 87 5.11 Mean Electrical Conductivity (EC) and Chemical
Composition of Some Ground Waters of Punjab and Rajasthan in India 87
5.12 Sulfur Content of Irrigation Water in Indonesia and Bangladesh 88
6.1 Effect of Different Sulfur-Containing and Sulfur-Free Fertilizer Treatments on Groundnuts in Sandy Loam Soil of Ludhiana, Punjab, India 93
6.2 Effect of Nitrogen and Sulfur Rates in Trials at Samrala, Punjab, India 95
6.3 Comparative Effect of Gypsum (G) and Pyrite (P) on Rice and Wheat Grown on Sodic Soil in Kamal, Haryana, India 98
6.4 Rice Response to Sulfur Application and Relative Efficiency of Nitrogen Utilization, South Sulawesi, Indonesia 99
6.5 Crop Response to Sulfur Fertilization in Selected African Countries 103
6.6 Number of Trials Grouped by Yield of Minus Sulfur Treatment on Cotton Expressed as 070 of Plus Sulfur Treatment of NPKs 104
6.7 Responses of Maize to Sulfur in Nigerian Savanna Soils 106 6.8 Effect of Sulfur-Containing Fertilizer on the Yield of Maize
in Different Regions of Northern Zimbabwe 109 6.9 Effect of Sulfur on Yields of Different Crops Grown on
Brazilian Cerrado Soils (Based on Field Experiments) 112 6.10 Adsorbed Sulfate in Cropped Brazilian Soils and Millet
Response to Sulfur Fertilization 112
XI
6.11 Changes in Available Sulfur in Soil After 7 Years of Cropping at IARI, New Delhi 117
6.12 Sulfur Deficiency and Response Research by Crops and Countries in the Tropics: A Summary 120
7.1 List of Field Crops and Crop Groups Used in Estimating Sulfur Requirements 129
7.2 Average Sulfur Uptake and Sulfur Uptake Coefficients for Specific Crop Groups 131
7.3 Estimated Aggregate Sulfur Uptake by Field Crops in Selected Developing Countries and World Regions, 1960-2000 132
7.4 Estimated Aggregate Sulfur Replacement Requirements by Field Crops in Selected Developing Countries and Regions Under Alternative Sulfur Replacement Coefficient Scenarios, 1960-2000 133
7.5 Estimated Sulfur Requirements for World Fertilizer Industry 134 7.6 Estimated Proportion of Sulfur Uptake by Specific Crop
Groups in Developing World Regions 136 7.7 Estimated Nitrogen:Sulfur and Phosphorus:Sulfur Ratios in
Aggregate Fertilizer Consumption in India and Brazil 138 7.8 Relative Contribution of Ammonium Sulfate to Regional
Nitrogen Consumption in the World 140 7.9 The Relative Contribution of Ammonium Sulfate and Single
Superphosphate to Nutrient Consumption in Selected Developing Countries 142
7.10 Estimated Consumption of Sulfur and Other Primary Nutrients in India and Brazil 143
7.11 Estimated Sulfur Requirements, Fertilizer Sulfur Supply, and Sulfur Gaps in Selected Countries During 1980 144
7.12 Estimated Sulfur Requirements, Fertilizer Sulfur Supply, and Sulfur Gaps in India 144
8.1 Sulfur-Containing Fertilizers and Other Substances 150 8.2 Estimated Total Nutrient Content of Selected Nitrogen and
Potassium Fertilizers: An Example 152 9.1 Patterns of Sulfur Demand in the United States: An
Example 160 9.2 Production of Sulfur by Countries and World Regions
During 1981 162 9.3 World Consumption of Sulfur and Allocation of Brimstone
for Nonacid Used During 1980 165 9.4 Production of Sulfuric Acid by Country and World Regions
During 1981 167 9.5 World Consumption and Regional Allocation of Sulfuric
Acid and Sulfur for Fertilizer Production During 1980 169
XII
9.6 World Consumption and Allocation of Sulfuric Acid and Sulfur to Fertilizer Sector During 1981 170
9.7 Patterns of World Trade for Brimstone During 1981 172 9.8 Sulfur Freight Rates and Their Contribution to International
Sulfur Prices 179 9.9 Estimated Sulfur Resources in the World 181 9.10 Location and Magnitude of Identified World Sulfur Reserves 182 9.11 Type and Location of Known Sulfur Resources in Individual
Countries of the World 184 9.12 Estimated Production of Phosphogypsum and Sulfur
Contained in Phospho gypsum in Selected Countries, Regions, and the World 187
10.1 Changes in Estimated Nitrogen:Sulfur and Phosphate:Sulfur Ratios in Total Fertilizer Consumption in India and Brazil Over Time 192
10.2 Estimated Proportion of Sulfur Uptake by Pulses and Oilseeds in India and Nigeria from 1960 to 2000 194
10.3 Nutrient Consumption, Sulfur Uptake, and Sulfur Supply in Selected Tropical Countries During 1970 and 1980 197
lOA Sulfur Additions, Removals, Balance and Replacement Requirements Under Subsistence and Modern Agriculture: Likely Alternative Scenarios 198
10.5 Priority Areas for Fertilizer Sulfur Research and Policy in Asia, Africa, and Latin America 206
10.6 Estimated Aggregate Sulfur Requirements for Field Crops in Selected Developing Tropical Countries and Regions, 1960-2000 209
10.7 Estimated World Sulfur Requirements as Crop Nutrient and for the Fertilizer Industry, 1960- 2000 209
10.8 Estimated Sulfur Requirements, Fertilizer Sulfur Supply, and Sulfur Gaps in Selected Tropical Countries During 1980 211
10.9 Sources of Sulfur and Sulfur Production in Developing Tropical Regions of the World During 1981 215
XIII
List of Figures
3.1 Regional Comparison of Agricultural Land per Agricultural Worker During 1965 and 1980 17
3.2 Components of Sulfur Supply and Demand in Soil-Plant-Atmosphere System 21
3.3 Role of Sulfur in Fertilizer Industry and Agricultural Production 23
3.4 Growth in Distribution of Plant Nutrients in India 27 3.5 Evolution of Sulfur-Containing Nitrogen and Phosphate
Fertilizer Use in Indian Agriculture 27 3.6 Loss in Paddy Rice Production Due to Sulfur Deficiency:
Based on Experimental Results From Indonesia 30 4.1 Effect of Cropping Pattern and Agricultural Modernization
on Average Sulfur Uptake 39 4.2 Levels of Sulfur Uptake by Indian Mustard at Different
Levels of Nitrogen and Sulfur Applications (Supply Sources: Urea for N; Gypsum for S) 42
4.3 Effect of Sulfur on Protein and Oil Content of Groundnuts and Mustard in Ludhiana Sandy Loam Soil in Punjab, India 49
5.1 Geographical Distribution of the Humid, Sub humid, Arid and Semiarid Tropics in the World 52
5.2 Effect of 20-30 Years of Cropping on Forms and Amounts of Sulfur in Two Soils of Brazil 66
5.3 Effect of Applied Sulfur and Nitrogen on Maize Yield in New Delhi, India 77
5.4 Changes in Sulfur Status Under Intensive Cropping and Different Fertilizer Treatments at IARI, New Delhi, India 80
5.5 Sulfur Deficiency and Changes in Sources of Sulfur to Crops in Soils From Clearance of Natural Fallow Through Cropping Cycle With No Application of Fertilizer Sulfur (not to scale) 82
6.1 Effect of Applied Sulfur (Gypsum) on High-Yielding Wheat Varieties in Light-Textured Soils in Ludhiana, Punjab, India, in 1971-73 (2-Year Mean Yields at Constant Levels of N, P, and K) 92
6.2 Effect of Single Superphosphate in Comparison with Triple Superphosphate and Diammonium Phosphate on Pod Yield of Groundnuts 94
6.3 Effects of Applied Sulfur on Grain Yield of Pulses in Punjab, India 96
6.4 Interactions of Sulfur and Phosphates on Grain Sorghum Yield in Venezuela 114
XIV
6.5 Countries in Which Sulfur Deficiency Exists and Crops on Which Sulfur Responses Have Been Reported in Tropical Asia 121
6.6 Countries in Which Sulfur Deficiency Exists and Crops on Which Sulfur Responses Have Been Reported in Tropical Africa 122
6.7 Countries in Which Sulfur Deficiency Exists and Crops on Which Sulfur Responses Have Been Reported in Tropical Latin America 123
7.1 A Generalized Relationship Between Crop Response and Sulfur Uptake 126
7.2 Estimated Proportion of Sulfur Uptake by Broad Crop Groups in Selected Developing Countries 135
7.3 World Trends in Production Capacity for Sulfur-Containing Nitrogen and Phosphate Fertilizers 139
7.4 Relative Contribution of Single Superphosphate to Regional P20 S Fertilizer Production Capacity in the World 141
8.1 The Effect of Source, Particle Size, and Sulfur Rate on Sulfate Leaching Losses From Fertilizer Materials 156
9.1 Estimated Percent Share of Sulfur Consumption Components in the Western World During 1980 171
9.2 Patterns of World Sulfur Production and Exports During 1981 174
9.3 Market Share in World Sulfur Imports by Different Regions and Countries During 1981 175
9.4 The Dynamics of Sulfur Prices in the United States (Average Annual Price) 178
10.1 Estimated Proportion of Sulfur Uptake by Cereal and Noncereal Food Crops in Selected Countries and Regions in the World 210
10.2 Estimated Sulfur Requirements, Fertilizer Sulfur Supply, and Sulfur Gaps in India: An Example 212
Acronyms and Abbreviations
Fertilizers and Chemicals
Al AS B Ba C Ca CAN CaCl2
Ca(H2P04h Cu DAP Fe FYM H2S H2S04
HOAc K K20 KH2P04
LiCI MAP Mg Mn Mo MOP N Na NaH2P04
NaHC03
NaOAc NH40Ac P P20 5
PAPR S Se S02 SO-2
4 SSP
aluminum ammonium sulfate boron barium carbon calcium calcium ammonium nitrate calcium chloride monocalcium phoshate copper diammonium phosphate iron farmyard mannure hydrogen sulfide sulfuric acid acetic acid potassium potassium, expressed as potassium oxide potassium dihydrogen phosphate lithium chloride mono ammonium phosphate magnesium manganese molybdenum muriate of potash (potassium chloride) nitrogen sodium sodium dihydrogen phosphate sodium bicarbonate sodium acetate ammonium acetate phosphorus phosphate, expressed as phosphorus pentoxide partially acidulated phosphate rock sulfur selenium sulfur dioxide sulfate ion single superphosphate
xv
XVI
TSP Zn
triple superphosphate zinc
Units of Measurements
Btu cm g GJ ha kcal kg km I m3
mCi meq mg ml mm mt ppm $ c.iJ. CPE DME DgME f.i.o. f.o.b.
Organizations
BARI BRRI CIAT FAO
FERTECON IARI ICRISAT
IFDC IFPRI IRRI
British thermal unit centimeter gram gigajoule hectare kilocalorie kilogram kilometer liter cubic meter millicurie milliequivalent milligram milliliter millimeter metric ton parts per million U.S. dollar cost, insurance, and freight centrally planned economies developed market economies developing market economies free in and out free on board
Bangladesh Agricultural Research Institute Bangladesh Rice Research Institute Centro Internacional de Agricultura Tropical Food and Agriculture Organization of the United Nations Fertilizer Economic Studies, Ltd. Indian Agricultural Research Institute International Crops Research Institute for the SemiArid Tropics International Fertilizer Development Center International Food Policy Research Institute International Rice Research Institute
ODA Sulexco UNESCO
UNIDO
USDA
Overseas Development Administration Sulfur Export Corporation
XVII
United Nations Educational, Scientific, and Cultural Organization United Nations Industrial Development Organization United States Department of Agriculture
XIX
Foreword
Fertilizer is a vital component of strategies for expanding foodproduction. The rapid growth in population and the widening food deficits inmany tropical countries of Asia, Africa, and Latin America call attention to those aspects of fertilization that have been neglected but are expected to yieldlarge economic payoffs in the future. Fertilizer sulfur falls into this category.
In the past fertilizer sulfur received little attention from researchers and policymakers since sulfur deficiency was not considered a serious problem. It was not a problem because of low crop yields, extensive cropping, and the incidental supply of sulfur through rain, irrigation water, manures, and sulfurcontaining fertilizers.
However, the situation has changed in the last three decades. Modernagriculture based on high crop yields, intensive cropping, improved crop varieties, and greater use of sulfur-free fertilizers and environmental regulations restricting sulfur emissions are creating large gaps between sulfur supply and sulfur requirements. Sulfur deficiencies are widespread and growing. Consequently, the full potential of a modern agricultural system in tropical countries is not being realized.
This research effort results from the recognition of the seriousness of the sulfur problem and its adverse impact on food production as well as IFDC's dedication to the development and transfer of economically efficient fertilizer technology to tropical countries. This study represents a comprehensive analysis of the technical and economic linkages between fertilizer sulfur and food production, and it provides guidelines for future directions in fertilizer sulfur research and public policy.
The project was jointly undertaken by Dr. 1. S. Kanwar, Director of Research, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), and Dr. Mohinder S. Mudahar, Economist, International Fertilizer Development Center (IFDC). Dr. Kanwar, an eminent soil scientist, spent his 1982183 sabbatical year at IFDC and participated in this research endeavor. This study is expected to provide needed impetus for national and international research and financial organizations to initiate and finance major fertilizer sulfur research and development programs.
The highlights of the study were published in 1983 as IFDC Technical Bulletin No. 27. It is hoped that this study will be of major significance to fertilizer researchers, extension agents, manufacturers, planners, and policymakers in their efforts to improve fertilizer use efficiency and alleviate world hunger.
Donald L. McCune Managing Director International Fertilizer Development Center
XXI
Acknowledgments
We are grateful to Dr. Donald L. McCune, Managing Director, IFDC, for inviting the first author to IFDC and suggesting that we study the problem of fertilizer sulfur and food production in relation to developing tropical countries of Asia, Africa, and Latin America; and to Dr. L. D. Swindale, Director General, ICRISAT, Hyderabad, India, for suggesting and encouraging the first author to spend his 1982183 sabbatical year at IFDC.
We thank Dr. R. K. Cunningham of the Overseas Development Administration (ODA) of the United Kingdom for making available the research reports on multiyear sulfur programs in Nigeria and Kenya, conducted under an ODA assistance programby Mr. A. R. Bromfield and his associates. We have used these reports freelyand acknowledged them in the text. We are grateful to Dr. G. W. Cooke, Honorary Scientist, Rothamsted Experimental Station and formerly Chief Scientific Officer, Agricultural Research Council, London, for helping us establish the contact with this source of information and for his valuable comments on an earlier draft of this study.
We gratefully acknowledge the encouragement, support, and commentsreceived from IFDC management and Board members during the course of this study. We are grateful to Dr. Paul L.G. Vlek, Director, IFDC AgroEconomic Division, and Mr. Travis P. Hignett, IFDC Special Consultant to the Managing Director, who read the previous draft of the manuscript and made valuable comments. The assistance provided by Mrs. Susan Highfield at different stages of the study is also gratefully acknowledged. Finally, we are thankful to the Word Processing staff for typing several drafts of the manuscript and to the Communications staff for editing, developing artwork, and preparing the manuscript for publication.
J. S. Kanwar and Mohinder S. Mudahar
