FERTILIZER SULFUR AND FOOD PRODUCTION

Fertilizer sulfur and foodproduction

by

1.S. KANWARICRISATHyderabadIndia

M.S. MUDAHARIFDCMuscle Shoals, AlabamaUSA

1986 Springer-Science+Business Media, B.Y:...."

Library of Congress Cataloging in Publication Data

Kanwar , J a swant Si ngh , 1922-Fe rt il i zer s u lfu r and foo d pr oduc t i on.

" J ul y 198 5."8i b l iog ra phy : p.I . Su l phu r ferti l i ze r s --Tr op i c s . 2 . Food s upp l y- ­

Tr op i cs. 3 . Su l phu r de f i ci enc y d i s e a s e s i n p la nt s - ­Tr op i c s. 4. Su l phu r industry--Tr op i cs . 5 . Su l phu rferti liz e r s - - Resea rc h- -T ro pi cs . 6 . Su lphu r f er tili ze r s -­Gove r nmen t po l i c y- -T r opi cs. 7. Su l phu r in nu t r i t ion .I . Mudah ar, Mohi nder S . 11 . I nt erna t iona l Fe r til izerDev el opmen t Cente r . 111 . Ti t l e .S653 .5 . S84 K36 1986 63 1 . 8 ' 25 8 5- 2 16 14

ISBN 978-90-247-3244-9 ISBN 978-94-017-1540-9 (eBook)DOI 10.1007/978-94-017-1540-9

Book Information

Paperback volume only available from the International Fertilizer DevelopmentCenter, c/o Mr . Paul L.G. Vlek, P.O. Box 2040, Muscle Shoals, Alabama,35662, USA, and from ICRISAT, Patancheru P.O., Andhra Pradesh 502324,India.

Copyright

© 1986 by Springer Science+Business Media DordrechtOriginally published by Martinus Nijhoff/Dr W. Junk Publishers, Dordrecht in 1986.

All rights reserved. No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by any means, mechanical,photocopying, recording, or otherwise, without the prior written permission ofthe publishers, Springer-Seience-Business Media, B.Y.

v

Table of Contents

List .of Tables ixList of Figures xiiiAcronyms and Abbreviations xvForeword xixAcknowledgments XXI

1 Introduction IStatement of the Problem IObjectives 3

2 Food and Nutrition Problems in Perspective 5Population and Food Production 5Magnitude and Location of Food Deficits 6Malnutrition in Developing Countries 8Sources of Calories and Protein Supply 11Components of Food Production 12

3 Fertilizer Sulfur in Strategies for Food Production 15Strategies for Expanding Food Production 15Fertilizer in Agricultural Development 16Importance of Sulfur 20Sulfur in the Fertilizer Industry 22The Sulfur Gap 25Social Cost of Inadequate Sulfur Use 29Economics of Fertilizer Sulfur 30

4 Sulfur in Plant, Animal, and Human Nutrition 33Function of Sulfur in Plant Nutrition 33Uptake and Translocation of Sulfur 33Sulfur Uptake by Different Crops 35Sulfur Application and Crop Quality 38Sulfur Interactions With Other Nutrients 41

Sand N Interactions 41Sand P Interactions 42Sand K Interactions 44Sand Ca, Mg Interactions 44S and Micronutrient Interactions 44Sand Mo Interactions 44Sand Se Interactions 44

Uptake and Recovery of Applied Fertilizer Sulfur 45Sulfur in Animal Nutrition 45Sulfur in Human Nutrition 47

VI

5

6

Status, Diagnosis, and Determinants of Sulfur DeficiencySulfur Status of Soils in the Tropics

Delineation of Tropical RegionsSulfur Status of Tropical Soils

Inorganic SulfurSulfate Forms and SourcesSulfates in Tropical SoilsAdsorbed Sulfates

Organic SulfurEster SulfatesCarbon-Bonded Sulfur CompoundsTransformation of Organic Sulfur

Diagnosis of Sulfur DeficiencySoil Testing MethodsSoil Tests and Sulfur Response CorrelationBiological MethodsTissue Testing for Sulfur Status

Determinants of Sulfur DeficiencySoil FactorsClimatic FactorsCrops, Cropping Systems, and Crop ResidueFertilizer Use and ManagementIrrigationIndustrialization and Environmental Policies

Conclusions and Research Agenda

Crop Response to Fertilizer Sulfur in the TropicsAsia

IndiaBangladeshSri LankaIndonesiaMalaysiaPhilippinesThailandPapua New GuineaSummary for Asia

AfricaWest AfricaEast Africa and Southern AfricaSummary for Africa

Latin AmericaBrazilVenezuela

51515153585861626464646667687072737575777983868989

919191989999

100100100101101102102106110110111113

VII

Costa Rica 113Mexico 113Colombia 115Chile 115West Indies 115Ecuador 116Nicaragua 116Summary for Latin America 116

Residual Effects of Fertilization With Sulfur 116Annual Crops 116Perennial Crops 118

Conclusions and Research Agenda 118

7 Estimating Sulfur Requirements, Supplies, and Gaps 125Determinants of Sulfur Uptake 125Determinants of Sulfur Replacement Requirements 126Model for Estimating Sulfur Requirements 126Data for Estimating Sulfur Requirements 128Estimated Aggregate Sulfur Requirements 130Estimated Sulfur Requirements by Crops 134Estimating Sulfur Requirements from Nitrogen and

Phosphorus Use 135Trends in Fertilizer Sulfur Supply 138Estimated Gaps in Sulfur Requirements and Sulfur Supply 142

8 Fertilizer Sulfur Sources and Supply Strategies 147Sulfur Sources 147

Atmospheric Accession 147Irrigation Water 147Organic Material and Crop Residues 148Fertilizers and Soil Amendments 148

Sulfur-Supplying Fertilizers and Soil Amendments 149Considerations for Formulating a Sulfur Supply Strategy 149Modification of Fertilizers to Supply Sulfur 154Research on Sulfur Fertilizers 154

Modified Phosphate-Sulfur Fertilizers 155Modified Nitrogen-Sulfur Fertilizers 155Replenishing Sulfur Lost Through Leaching 155

Criteria for Evaluating Fertilizer Sulfur Sources 156

9 World Sulfur Situation, Outlook, and Public Policy 159Sulfur Supply and Demand Components 159Patterns and Trends in Sulfur Production 160Patterns and Trends in Sulfur Consumption 161

VIII

Patterns and Trends in Sulfuric Acid ProductionPatterns and Trends in Sulfuric Acid ConsumptionPatterns and Determinants of World Trade in SulfurSulfur Trade Policies in Selected CountriesBehavior of International Sulfur PricesSulfur Reserves, Resources, and Their UseProduction and Use of Phosphogypsum

164168172176177180186

10 Summary, Conclusions, and Recommendations 191Sulfur - A Neglected Fertilizer Nutrient 191Tropics and Food Production - The Target Area of Study 191Sulfur in Plant Nutrition 192Sulfur in Food Production and Human Nutrition 193Sulfur Status in the Tropics - Additions 194

Sulfur-Supplying Capacity of Tropical Soils 194Contribution of Sulfur From External Sources 195

Sulfur Status in the Tropics - Removals 196Sulfur Balance Sheet and Likely Scenarios 200

Subsistence Agriculture 200Modern Agriculture 200

Magnitude of Sulfur Deficiency in Tropical Soils 201Determining Sulfur Deficiency in the Tropics 202Crop Response to Fertilizer Sulfur 203Priority Areas for Fertilizer Sulfur Research 205Sulfur Strategies for Meeting the Challenge 205Estimating Sulfur Requirements and Gaps 207Evaluation of Alternative Fertilizer Sulfur Materials 211Economic and Policy Analysis of Fertilizer Sulfur 213Pricing of Fertilizer Sulfur 213Sulfur Situation, Resources, Trade, and Outlook 214Sulfur Trade Policies 216Phosphogypsum: A Source of Fertilizer Sulfur 216Need for Information Related to Fertilizer Sulfur 217Fertilizer Sulfur Use Recommendations 217Fertilizer Sulfur Regulation and Labeling 218Sulfur, Environmental Protection, and Food Production 218Implications for Research and Public Policy 219

Priorities for National Research Programs 219Priorities for International Research Programs 220

ReferencesAppendixes

223241

List of Tables

IX

2.1 Regional Distribution of World Population and FoodProduction During 1981 6

2.2 Estimated Food Production, Consumption, and Deficits inSelected Countries and Regions of Developing MarketEconomies 9

2.3 Share and Magnitude of Population ConsideredUndernourished in Selected Countries and Regions ofDeveloping Market Economies 10

2.4 Relative Contribution of Individual Food Items to AverageDaily Per Capita Calorie Supply by Region and EconomicGroup, 1972-74 12

2.5 Relative Contribution of Individual Food Items to AverageDaily Per Capita Protein Supply by Region and EconomicGroup, 1972-74 13

2.6 Relative Contribution of Individual Commodities to FoodProduction in Developing Market Economies During 1981 14

3.1 Level, Pattern, and Growth in Fertilizer Consumption forWorld Regions in 1981 18

3.2 Sulfur Removed by Selected Crops in Brazil 203.3 Average Sulfur Use and Loss in Manufacturing Selected

Fertilizer Products and Intermediates 243.4 Impact of Changing Technology on Average Annual Sulfur

Requirements in Tropical Agriculture: A Case of Wheat andRice Cropping System 28

3.5 Average Response of Rice to Urea and Ammonium Sulfatein South Sulawesi, Indonesia 29

4.1 Sulfur Content of Various Plant Species 354.2 Estimated Nutrients (S and N, P, K) Removed by Different

Crops 364.3 Effect of Sulfur on Yield and Chemical Composition of

Groundnuts 404.4 Effect of Levels and Sources of Phosphorus on the Yield

and Sulfur and Phosphorus Concentrations in GroundnutFoliage 43

4.5 Fertilizer Sulfur Use Efficiency 464.6 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 EssentialAmino Acids and Sulfur-Containing Amino Acid Content ofCereals in India 48

X

5.1 Estimated Area of Major Soil Groups in the Humid Tropics 525.2 Estimated Area of Major Soil Groups in the Semiarid

Tropics 535.3 Total Sulfur Values for a Range of Soils From Tropical

Regions 545.4 Ratio of Sulfur to Other Nutrients in West African Soils 575.5 Sulfur Content in Some Nigerian Soils (On Dry-Matter

Basis) 585.6 Natural and Artificial Sources of Sulfur Generation on the

Earth 605.7 Mean Carbon:Nitrogen:Sulfur Ratios in Selected Soils in the

World 655.8 Critical Levels of Sulfur in Soil for Different Crops and in

Different Countries 695.9 The Effect of Liming and Leaching on Soil Sulfate, Total

Soil Sulfur, and the Amounts of Sulfate Leached 845.10 Changes in Soluble Sulfate in Soil at Various Depths and

Different Periods 875.11 Mean Electrical Conductivity (EC) and Chemical

Composition of Some Ground Waters of Punjab andRajasthan in India 87

5.12 Sulfur Content of Irrigation Water in Indonesia andBangladesh 88

6.1 Effect of Different Sulfur-Containing and Sulfur-FreeFertilizer Treatments on Groundnuts in Sandy Loam Soil ofLudhiana, 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 Riceand Wheat Grown on Sodic Soil in Kamal , Haryana, India 98

6.4 Rice Response to Sulfur Application and Relative Efficiencyof Nitrogen Utilization, South Sulawesi, Indonesia 99

6.5 Crop Response to Sulfur Fertilization in Selected AfricanCountries 103

6.6 Number of Trials Grouped by Yield of Minus SulfurTreatment on Cotton Expressed as % of Plus SulfurTreatment of NPKs 104

6.7 Responses of Maize to Sulfur in Nigerian Savanna Soils 1066.8 Effect of Sulfur-Containing Fertilizer on the Yield of Maize

in Different Regions of Northern Zimbabwe 1096.9 Effect of Sulfur on Yields of Different Crops Grown on

Brazilian Cerrado Soils (Based on Field Experiments) 1126.10 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 ofCropping at IARI, New Delhi 117

6.12 Sulfur Deficiency and Response Research by Crops andCountries in the Tropics: A Summary 120

7.1 List of Field Crops and Crop Groups Used in EstimatingSulfur Requirements 129

7.2 Average Sulfur Uptake and Sulfur Uptake Coefficients forSpecific Crop Groups 131

7.3 Estimated Aggregate Sulfur Uptake by Field Crops inSelected Developing Countries and World Regions,1960-2000 132

7.4 Estimated Aggregate Sulfur Replacement Requirements byField Crops in Selected Developing Countries and RegionsUnder Alternative Sulfur Replacement Coefficient Scenarios,1960-2000 133

7.5 Estimated Sulfur Requirements for World Fertilizer Industry 1347.6 Estimated Proportion of Sulfur Uptake by Specific Crop

Groups in Developing World Regions 1367.7 Estimated Nitrogen:Sulfur and Phosphorus:Sulfur Ratios in

Aggregate Fertilizer Consumption in India and Brazil 1387.8 Relative Contribution of Ammonium Sulfate to Regional

Nitrogen Consumption in the World 1407.9 The Relative Contribution of Ammonium Sulfate and Single

Superphosphate to Nutrient Consumption in SelectedDeveloping Countries 142

7.10 Estimated Consumption of Sulfur and Other PrimaryNutrients in India and Brazil 143

7.11 Estimated Sulfur Requirements, Fertilizer Sulfur Supply, andSulfur Gaps in Selected Countries During 1980 144

7.12 Estimated Sulfur Requirements, Fertilizer Sulfur Supply, andSulfur Gaps in India 144

8.1 Sulfur-Containing Fertilizers and Other Substances 1508.2 Estimated Total Nutrient Content of Selected Nitrogen and

Potassium Fertilizers: An Example 1529.1 Patterns of Sulfur Demand in the United States: An

Example 1609.2 Production of Sulfur by Countries and World Regions

During 1981 1629.3 World Consumption of Sulfur and Allocation of Brimstone

for Nonacid Used During 1980 1659.4 Production of Sulfuric Acid by Country and World Regions

During 1981 1679.5 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 andSulfur to Fertilizer Sector During 1981 170

9.7 Patterns of World Trade for Brimstone During 1981 1729.8 Sulfur Freight Rates and Their Contribution to International

Sulfur Prices 1799.9 Estimated Sulfur Resources in the World 1819.10 Location and Magnitude of Identified World Sulfur Reserves 1829.11 Type and Location of Known Sulfur Resources in Individual

Countries of the World 1849.12 Estimated Production of Phosphogypsum and Sulfur

Contained in Phosphogypsum in Selected Countries,Regions, and the World 187

10.1 Changes in Estimated Nitrogen:Sulfur and Phosphate:SulfurRatios in Total Fertilizer Consumption in India and BrazilOver Time 192

10.2 Estimated Proportion of Sulfur Uptake by Pulses andOilseeds in India and Nigeria from 1960 to 2000 194

10.3 Nutrient Consumption, Sulfur Uptake, and Sulfur Supply inSelected Tropical Countries During 1970 and 1980 197

10.4 Sulfur Additions, Removals, Balance and ReplacementRequirements Under Subsistence and Modern Agriculture:Likely Alternative Scenarios 198

10.5 Priority Areas for Fertilizer Sulfur Research and Policy inAsia, Africa, and Latin America 206

10.6 Estimated Aggregate Sulfur Requirements for Field Crops inSelected Developing Tropical Countries and Regions,1960-2000 209

10.7 Estimated World Sulfur Requirements as Crop Nutrient andfor the Fertilizer Industry, 1960-2000 209

10.8 Estimated Sulfur Requirements, Fertilizer Sulfur Supply, andSulfur Gaps in Selected Tropical Countries During 1980 211

10.9 Sources of Sulfur and Sulfur Production in DevelopingTropical Regions of the World During 1981 215

List of Figures

XIII

3.1 Regional Comparison of Agricultural Land per AgriculturalWorker 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 AgriculturalProduction 23

3.4 Growth in Distribution of Plant Nutrients in India 273.5 Evolution of Sulfur-Containing Nitrogen and Phosphate

Fertilizer Use in Indian Agriculture 273.6 Loss in Paddy Rice Production Due to Sulfur Deficiency:

Based on Experimental Results From Indonesia 304.1 Effect of Cropping Pattern and Agricultural Modernization

on Average Sulfur Uptake 394.2 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 Groundnutsand Mustard in Ludhiana Sandy Loam Soil in Punjab, India 49

5.1 Geographical Distribution of the Humid, Subhumid, Aridand Semiarid Tropics in the World 52

5.2 Effect of 20- 30 Years of Cropping on Forms and Amountsof Sulfur in Two Soils of Brazil 66

5.3 Effect of Applied Sulfur and Nitrogen on Maize Yield inNew Delhi, India 77

5.4 Changes in Sulfur Status Under Intensive Cropping andDifferent Fertilizer Treatments at IARI, New Delhi, India 80

5.5 Sulfur Deficiency and Changes in Sources of Sulfur toCrops in Soils From Clearance of Natural Fallow ThroughCropping Cycle With No Application of Fertilizer Sulfur(not to scale) 82

6.1 Effect of Applied Sulfur (Gypsum) on High-Yielding WheatVarieties 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 TripleSuperphosphate and Diammonium Phosphate on Pod Yieldof Groundnuts 94

6.3 Effects of Applied Sulfur on Grain Yield of Pulses inPunjab, India 96

6.4 Interactions of Sulfur and Phosphates on Grain SorghumYield in Venezuela 114

XIV

6.5 Countries in Which Sulfur Deficiency Exists and Crops onWhich Sulfur Responses Have Been Reported in TropicalAsia 121

6.6 Countries in Which Sulfur Deficiency Exists and Crops onWhich Sulfur Responses Have Been Reported in TropicalAfrica 122

6.7 Countries in Which Sulfur Deficiency Exists and Crops onWhich Sulfur Responses Have Been Reported in TropicalLatin America 123

7.1 A Generalized Relationship Between Crop Response andSulfur Uptake 126

7.2 Estimated Proportion of Sulfur Uptake by Broad CropGroups in Selected Developing Countries 135

7.3 World Trends in Production Capacity for Sulfur-ContainingNitrogen and Phosphate Fertilizers 139

7.4 Relative Contribution of Single Superphosphate to RegionalP20S Fertilizer Production Capacity in the World 141

8.1 The Effect of Source, Particle Size, and Sulfur Rate onSulfate Leaching Losses From Fertilizer Materials 156

9.1 Estimated Percent Share of Sulfur ConsumptionComponents in the Western World During 1980 171

9.2 Patterns of World Sulfur Production and Exports During1981 174

9.3 Market Share in World Sulfur Imports by Different Regionsand Countries During 1981 175

9.4 The Dynamics of Sulfur Prices in the United States (AverageAnnual Price) 178

10.1 Estimated Proportion of Sulfur Uptake by Cereal andNoncereal Food Crops in Selected Countries and Regions inthe World 210

10.2 Estimated Sulfur Requirements, Fertilizer Sulfur Supply, andSulfur Gaps in India: An Example 212

Acronyms and Abbreviations

Fertilizers and Chemicals

xv

AlASBBaCCaCANCaCl2

Ca(H2P04}zCuDAPFeFYMH2SH2S04

HOAcKK20KH2P04

LiCIMAPMgMnMoMOPNNaNaH2P04

NaHC03NaOAcNH40Ac

PP20SPAPRSSeS02SO-2

4SSP

aluminumammonium sulfateboronbariumcarboncalciumcalcium ammonium nitratecalcium chloridemonocalcium phoshatecopperdiammonium phosphateironfarmyard mannurehydrogen sulfidesulfuric acidacetic acidpotassiumpotassium, expressed as potassium oxidepotassium dihydrogen phosphatelithium chloridemonoammonium phosphatemagnesiummanganesemolybdenummuriate of potash (potassium chloride)nitrogensodiumsodium dihydrogen phosphatesodium bicarbonatesodium acetateammonium acetatephosphorusphosphate, expressed as phosphorus pentoxidepartially acidulated phosphate rocksulfurseleniumsulfur dioxidesulfate ionsingle superphosphate

XVI

TSPZn

triple superphosphatezinc

Units of Measurements

BtucmgOJhakcalkgkmIm3

mCimeqmgmlmmmtppm$c.i.f.CPEDMEDgMEf.i,o,f.o.b.

Organizations

BARIBRRICIATFAO

FERTECONIARIICRISAT

IFDCIFPRIIRRI

British thermal unitcentimetergramgigajoulehectarekilocaloriekilogramkilometerlitercubic metermillicuriemilliequivalentmilligrammillilitermillimetermetric tonparts per millionU.S. dollarcost, insurance, and freightcentrally planned economiesdeveloped market economiesdeveloping market economiesfree in and outfree on board

Bangladesh Agricultural Research InstituteBangladesh Rice Research InstituteCentro Internacional de Agricultura TropicalFood and Agriculture Organization of the UnitedNationsFertilizer Economic Studies, Ltd.Indian Agricultural Research InstituteInternational Crops Research Institute for the Semi­Arid TropicsInternational Fertilizer Development CenterInternational Food Policy Research InstituteInternational Rice Research Institute

ODASulexcoUNESCO

UNIDO

USDA

XVII

Overseas Development AdministrationSulfur Export CorporationUnited Nations Educational, Scientific, and CulturalOrganizationUnited Nations Industrial Development Organiza­tionUnited States Department of Agriculture

XIX

Foreword

Fertilizer is a vital component of strategies for expanding food production.The rapid growth in population and the widening food deficits inmanytropical countries of Asia, Africa, and Latin America call attention to thoseaspects 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 andpolicymakers since sulfur deficiency was not considered a serious problem.It was not a problem because of low crop yields, extensive cropping, andthe incidental supply of sulfur through rain, irrigation water, manures, andsulfurcontaining fertilizers.

However, the situation has changed in the last three decades. Moder­nagriculture based on high crop yields, intensive cropping, improved cropvarieties, 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 intropical countries is not being realized.

This research effort results from the recognition of the seriousness of thesulfur problem and its adverse impact on food production as well asIFDC's dedication to the development and transfer of economically ef­ficient fertilizer technology to tropical countries. This study represents acomprehensive analysis of the technical and economic linkages between fer­tilizer sulfur and food production, and it provides guidelines for futuredirections in fertilizer sulfur research and public policy.

The project was jointly undertaken by Dr. J. 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 1982/83 sabbatical year at IFDC and participated in this researchendeavor. This study is expected to provide needed impetus for national andinternational research and financial organizations to initiate and financemajor fertilizer sulfur research and development programs.

The highlights of the study were published in 1983 as IFDC TechnicalBulletin No. 27. It is hoped that this study will be of major significance tofertilizer researchers, extension agents, manufacturers, planners, and policy­makers in their efforts to improve fertilizer use efficiency and alleviateworld hunger.

Donald L. McCuneManaging DirectorInternational Fertilizer Development Center

XXI

Acknowledgments

We are grateful to Dr. Donald L. McCune, Managing Director, IFDC, forinviting the first author to IFDC and suggesting that we study the problemof fertilizer sulfur and food production in relation to developing tropicalcountries 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 1982/83 sabbatical year at IFDC.

We thank Dr. R. K. Cunningham of the Overseas Development Adminis­tration (aDA) of the United Kingdom for making available the researchreports on multiyear sulfur programs in Nigeria and Kenya, conducted un­der an aDA assistance programby Mr. A. R. Bromfield and his associates.We have used these reports freelyand acknowledged them in the text. We aregrateful to Dr. G. W. Cooke, Honorary Scientist, Rothamsted ExperimentalStation 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 ofthis study. We are grateful to Dr. Paul L.G. Vlek, Director, IFDC Agro­Economic Division, and Mr. Travis P. Hignett, IFDC Special Consultant tothe Managing Director, who read the previous draft of the manuscript andmade valuable comments. The assistance provided by Mrs. Susan Highfieldat different stages of the study is also gratefully acknowledged. Finally, weare thankful to the Word Processing staff for typing several drafts of themanuscript and to the Communications staff for editing, developing art­work, and preparing the manuscript for publication.

J. S. Kanwar andMohinder S. Mudahar