Rainfed Agriculture Unlocking the Potential

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Rainfed Agriculture:Unlocking the Potential


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Comprehensive Assessment of Water Management in Agriculture Series

Titles Available

Volume 1. Water Productivity in Agriculture: Limits and Opportunities for ImprovementEdited by Jacob W. Kijne, Randolph Barker and David Molden

Volume 2. Environment and Livelihoods in Tropical Coastal Zones: ManagingAgricultureFisheryAquaculture ConflictsEdited by Chu Thai Hoanh, To Phuc Tuong, John W. Gowing and Bill Hardy

Volume 3. The Agriculture Groundwater Revolution: Opportunities and Threats toDevelopmentEdited by Mark Giordano and Karen G. Villholth

Volume 4. Irrigation Water Pricing: The Gap Between Theory and PracticeEdited by Franois Molle and Jeremy Berkoff

Volume 5. Community-based Water Law and Water Resource Management Reform inDeveloping CountriesEdited by Barbara van Koppen, Mark Giordano and John Butterworth

Volume 6. Conserving Land, Protecting WaterEdited by Deborah Bossio and Kim Geheb

Volume 7. Rainfed Agriculture: Unlocking the PotentialEdited by Suhas P. Wani, Johan Rockstrm and Theib Oweis


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Rainfed Agriculture:Unlocking the Potential

Edited by

Suhas P WaniICRISAT, India

Johan RockstrmSEI, Sweden

and

Theib OweisICARDA, Syria

in association with
http://www.cabi.org/


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CABI is a trading name of CAB International

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CAB International 2009. All rights reserved. No part of this publication maybe reproduced in any form or by any means, electronically, mechanically, byphotocopying, recording or otherwise, without the prior permission of thecopyright owners.

A catalogue record for this book is available from the British Library,London, UK.

Library of Congress Cataloging-in-Publication Data

Rainfed agriculture : unlocking the potential / edited by Suhas P. Wani,Johan Rockstrm, and Theib Oweis.p. cm. -- (Comprehensive assessment of water management in agriculture

series ; 7)Includes bibliographical references and index.ISBN 978-1-84593-389-0 (alk. paper)

1. Dry farming--Asia. 2. Dry farming--Africa. 3. Water in agriculture--Asia.4. Water in agriculture--Africa. 5. Watershed management--Asia. 6. Watershedmanagement--Africa. I. Wani, S. P. II. Rockstrm, Johan. III. Oweis, TheibYousef. IV. Series.

SB110.R325 2009

631.586--dc22 2008031275

ISBN-13: 978 1 84593 389 0

Typeset by Columns Design Ltd, Reading, UK.Printed and bound in the UK by the MPG Books Group.
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Contents

Contributors vii

Series Foreword x

Foreword xii

Preface xiii

Acknowledgements xv

1 Rainfed Agriculture Past Trends and Future Prospects 1S.P. Wani, T.K. Sreedevi, J. Rockstrm and Y.S. Ramakrishna

2 Zooming in on the Global Hotspots of Rainfed Agriculture in 36Water-constrained Environments

J. Rockstrm and L. Karlberg

3 Water Resource Implications of Upgrading Rainfed Agriculture 44Focus on Green and Blue Water Trade-offs

L. Karlberg, J. Rockstrm and M. Falkenmark

4 TectonicsClimate-linked Natural Soil Degradation and its Impact 54in Rainfed Agriculture: Indian Experience

D.K. Pal, T. Bhattacharyya, P. Chandran and S.K. Ray

5 Determinants of Crop Growth and Yield in a Changing Climate 73P.K. Aggarwal

6 Yield Gap Analysis: Modelling of Achievable Yields at Farm Level 81P. Singh, P.K. Aggarwal, V.S. Bhatia, M.V.R. Murty, M. Pala, T. Oweis, B. Benli,K.P.C. Rao and S.P. Wani

7 Can Rainfed Agriculture Feed the World? An Assessment of 124Potentials and Risk

C. de Fraiture, L. Karlberg and J. Rockstrm

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8 Opportunities for Improving Crop Water Productivity through Genetic 133Enhancement of Dryland Crops

C.L.L. Gowda, R. Serraj, G. Srinivasan, Y.S. Chauhan, B.V.S. Reddy, K.N. Rai,S.N. Nigam, P.M. Gaur, L.J. Reddy, S.L. Dwivedi, H.D. Upadhyaya, P.H. Zaidi,H.K. Rai, P. Maniselvan, R. Follkerstma and M. Nalini

9 Water Harvesting for Improved Rainfed Agriculture in the Dry 164Environments

T. Oweis and A. Hachum

10 Supplemental Irrigation for Improved Rainfed Agriculture in WANA Region 182T. Oweis and A. Hachum

11 Opportunities for Water Harvesting and Supplemental Irrigation for 197

Improving Rainfed Agriculture in Semi-arid AreasP. Pathak, K.L. Sahrawat, S.P. Wani, R.C. Sachan and R. Sudi

12 Integrated Farm Management Practices and Upscaling the Impact for 222Increased Productivity of Rainfed Systems

T.K. Sreedevi and S.P. Wani

13 Challenges of Adoption and Adaptation of Land and Water Management 258Options in Smallholder Agriculture: Synthesis of Lessons and Experiences

B. Shiferaw, J. Okello and V. Ratna Reddy

14 Scaling-out Community Watershed Management for Multiple Benefits in 276Rainfed Areas

P.K. Joshi, A.K. Jha, S.P. Wani and T.K. Sreedevi

Index 292

vi Contents


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Contributors

P.K. Aggarwal, Head of Division, Indian Agricultural Research Institute, New Delhi 110 012,India. Email: [email protected]

B. Benli,International Center for Agricultural Research Institute in the Dry Areas (ICARDA), POBox 5466, Aleppo, Syria.

V.S. Bhatia, Crop Physiologist, National Research Centre for Soybean (NRCS), Khandwa Road,Indore 452 017, Madhya Pradesh, India. Email: [email protected]

T. Bhattacharyya,Principal Scientist, Division of Soil Resource Studies, National Bureau of SoilSurvey & Land Use Planning, Amravati Road, Nagpur 440 010, Maharashtra, India. Email:[email protected]

P. Chandran, Division of Soil Resource Studies, National Bureau of Soil Survey & Land UsePlanning, Amravati Road, Nagpur 440 010, Maharashtra, India.

Y.S. Chauhan, Plant Sciences, Department of Primary Industries and Fisheries, Kingaroy,Queensland, Australia (formerly with International Crops Research Institute for the Semi-AridTropics, Patancheru 502 324, Andhra Pradesh, India). Email: [email protected]

C. de Fraiture,International Water Management Institute, PO Box 2075, Colombo, Sri Lanka.Email: [email protected]

S.L. Dwivedi, Visiting Scientist (Genetic Resources), International Crops Research Institute

for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, Andhra Pradesh, India. Email:[email protected]

M. Falkenmark, Professor, Stockholm International Water Institute (SIWI), Drottninggatan 33,SE-111 51 Stockholm, Sweden. Email: [email protected]

R. Follkerstma, De Ruiter Seeds Inc., Leeuwenhoekweg 52 2661, CZ, Bergschenhoek, theNetherlands. Email: [email protected]

P.M. Gaur,Principal Scientist (Chickpea Breeding), International Crops Research Institute for theSemi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

C.L.L. Gowda, Global Theme Leader, Crop Improvement, International Crops Research Institutefor the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: c.gowda@

cgiar.orgA. Hachum, Consultant, Integrated Water and Land Management Program, International Center

for Agricultural Research in the Dry Areas (ICARDA,) Aleppo, Syria.A.K. Jha, Senior Research Associate, National Centre for Agricultural Economics and Policy

Research (NCAP), Library Avenue, Pusa, New Delhi 110 01 (formerly with International CropsResearch Institute for the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India).Email: [email protected]

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P.K. Joshi, Director, National Centre for Agricultural Economics and Policy Research, LibraryAvenue, Pusa, New Delhi 110 012, India. Email: [email protected]

L. Karlberg, Stockholm Environment Institute, Stockholm, Sweden. Email: [email protected]. Maniselvan, Vegetable Breeder, BISCO Seeds India Pvt Ltd, India.M.V.R. Murty, International Crops Research Institute for the Semi-Arid Tropics, Patancheru 502

324, Andhra Pradesh, India. Email: [email protected]. Nalini, Senior Scientist, Cell Biology, International Crops Research Institute for the Semi-Arid

Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

S.N. Nigam,Principal Scientist (Groundnut Breeding), International Crops Research Institute forthe Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

J. Okello,Department of Agricultural Economics, University of Nairobi, PO Box 29053, Nairobi00625, Kenya. Email: [email protected]

T. Oweis, Director, Integrated Water and Land Management Program, International Center forAgricultural Research in the Dry Areas (ICARDA), Aleppo, Syria. Email: [email protected]

D.K. Pal,Principal Scientist and Head, Division of Soil Resource Studies, National Bureau of SoilSurvey & Land Use Planning, Amravati Road, Nagpur 440 010, Maharashtra, India. Email:

[email protected]

M. Pala,International Center for Agricultural Research in the Dry Areas (ICARDA), PO Box 5466,Aleppo, Syria.

P. Pathak,Principal Scientist (Soil & Water Management), International Crops Research Institute forthe Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

H.K. Rai,Assistant Professor, S K University of Agriculture & Technology, Srinagar, India. Email:[email protected]

K.N. Rai, Principal Scientist (Pearl Millet Breeding), Global Theme on Crop Improvement,International Crops Research Institute for the Semi-Arid Tropics, Patancheru 502 324, Andhra

Pradesh, India. Email: [email protected]

Y.S. Ramakrishna, Director, Central Research Institute for Dryland Agriculture, Santoshnagar,Hyderabad 500 059, Andhra Pradesh, India. Email: [email protected]

K.P.C. Rao, International Center for Research on Agroforestry (ICRAF), Nairobi, Kenya. Email:[email protected]

S.K. Ray,Division of Soil Resource Studies, National Bureau of Soil Survey & Land Use Planning,Amravati Road, Nagpur 440 010, Maharashtra, India.

B.V.S. Reddy, Principal Scientist (Sorghum Breeding), International Crops Research Institute forthe Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

L.J. Reddy, D.No.46, ICRISAT Colony Phase I, Brg. Said Road, Secunderabad 500 009, India.Email: [email protected]

V. Ratna Reddy, Centre for Economics and Soil Studies (CESS), Nizamia Observatory Campus,Begumpet, Hyderabad 500 016, Andhra Pradesh, India. Email: [email protected]

J. Rockstrm,Executive Director, Stockholm Environment Institute, Stockholm, Sweden. Email:[email protected]

R.C. Sachan, Visiting Scientist, Global Theme on Agroecosystems, International Crops ResearchInstitute for the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email:

[email protected]. Sahrawat, Visiting Scientist (Soil Chemistry), International Crops Research Institute for theSemi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

R. Serraj, Senior Scientist, Crop & Environmental Sciences Division, International Rice ResearchInstitute, DAPO Box 7777, Metro Manila, Philippines. Email: [email protected]

B. Shiferaw,Principal Scientist and Program Leader (Markets, Institutions, Policies and Impacts),International Crops Research Institute for the Semi-Arid Tropics, PO Box 36063, Nairobi

00623, Kenya (formerly at ICRISAT, Patancheru 502 324, Andhra Pradesh, India). Email:

[email protected]

viii Contributors


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P. Singh,Principal Scientist (Soil Science), International Crops Research Institute for the Semi-AridTropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

T.K. Sreedevi, Scientist, Global Theme on Agroecosystems, International Crops Research Institute

for the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

G. Srinivasan,Director AOU, University of California, Fresno, USA.R. Sudi,Lead Scientific Officer, Global Theme on Agroecosystems, International Crops Research

Institute for the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email:[email protected]

H.D. Upadhyaya, Principal Scientist, Genetic Resources, International Crops Research Institutefor the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

S.P. Wani, Principal Scientist (Watersheds) and Regional Theme Coordinator (Asia), Global

Theme on Agroecosystems, International Crops Research Institute for the Semi-Arid Tropics,Patancheru 502 324, Andhra Pradesh, India. Email: [email protected]

P.H. Zaidi, Scientist, Global Maize Program, CIMMYTs Asia Regional Office, Patancheru 502324, Medak Dist., Andhra Pradesh, India. Email: [email protected]

Contributors ix


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Series Foreword: Comprehensive Assessment ofWater Management in Agriculture

x

There is broad consensus on the need to improvewater management and to invest in water for foodas these are critical to meeting the MillenniumDevelopment Goals (MDGs). The role of water infood and livelihood security is a major issue ofconcern in the context of persistent poverty and

continued environmental degradation. Althoughthere is considerable knowledge on the issue ofwater management, an overarching picture onthe waterfoodlivelihoodsenvironment nexus ismissing, leaving uncertainties about managementand investment decisions that will meet both foodand environmental security objectives.

The Comprehensive Assessment of WaterManagement in Agriculture (CA) is an inno-vative, multi-institute process aimed at identi-

fying existing knowledge and stimulatingthought on ways to manage water resources tocontinue meeting the needs of both humansand ecosystems. The CA critically evaluates thebenefits, costs and impacts of the past 50 yearsof water development and challenges to watermanagement currently facing communities. Itassesses innovative solutions and exploresconsequences of potential investment andmanagement decisions. The CA is designed asa learning process, engaging networks ofstakeholders to produce knowledge synthesisand methodologies. The main output of the CAis an assessment report that aims to guideinvestment and management decisions in thenear future, considering their impact over thenext 50 years in order to enhance food and

environmental security to support the achieve-ment of the MDGs. This assessment report isbacked by CA research and knowledge-sharingactivities.

The primary assessment research findingsare presented in a series of books that form

the scientific basis for the ComprehensiveAssessment of Water Management in Agriculture.The books cover a range of vital topics in theareas of water, agriculture, food security andecosystems the entire spectrum of developingand managing water in agriculture, from fullyirrigated to fully rainfed lands. They are aboutpeople and society, why they decide to adoptcertain practices and not others and, in par-ticular, how water management can help poor

people. They are about ecosystems howagriculture affects ecosystems, the goods andservices ecosystems provide for food security andhow water can be managed to meet both foodand environmental security objectives. This is theseventh book in the series.

Effectively managing water to meet food andenvironmental objectives will require the con-certed action of individuals from across severalprofessions and disciplines farmers, fishers,water managers, economists, hydrologists,irrigation specialists, agronomists and socialscientists. The material presented in this bookrepresents an effort to bring a diverse group ofpeople together to present a truly cross-disci-plinary perspective on rainfed agriculture. Thecomplete set of books should be invaluable for


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resource managers, researchers and field imple-menters. These books will provide sourcematerial from which policy statements, practical

manuals and educational and training materialcan be prepared.

The CA is done by a coalition of partners thatincludes 11 Future Harvest agricultural researchcentres supported by the Consultative Group onInternational Agricultural Research (CGIAR), theFood and Agriculture Organization of the UnitedNations (FAO) and partners from some 80research and development institutes globally. Co-sponsors of the assessment, institutes that are

interested in the results and help frame theassessment, are the Ramsar Convention, theConvention on Biological Diversity, the FAO and

the CGIAR.For production of this book, financial support

from the governments of the Netherlands andSwitzerland for the Comprehensive Assessmentis appreciated.

David Molden

Series EditorInternational Water Management Institute

Sri Lanka

Series Foreword xi


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xii

Foreword

Most of the 852 million poor people in the worldlive in the developing countries of Asia and Africa,more so in drylands/rainfed areas. These rainfedareas are hotbeds of poverty, malnutrition, waterscarcity, severe land degradation and poorphysical and social infrastructure. Though rainfedagriculture constitutes 80% of global agricultureand plays a crucial role in achieving food security,increasing water scarcity and climate changethreaten to affect rainfed areas and their peoples

owing to their vulnerability to drought during thecrop-growing season.

A Comprehensive Assessment (CA) of Waterfor Food and Water for Life, undertaken by aconsortium of dedicated scientists from differentinstitutions and rainfed areas and coordinated bythe International Crops Research Institute for theSemi-Arid Tropics (ICRISAT), revealed that globalfood security is possible with existing waterresources. However, it calls for considerable

efforts to improve water management to enhancewater use efficiency in all sectors.

The Comprehensive Assessment demon-strated that current farmers yields in rainfed areasare two- to fivefold lower than achievablepotential yields and that current rainwater useefficiency is only 3545% in most rainfed areas.Water used for food production in rainfed areas isalmost threefold higher than that used in irrigatedsystems. Long-term experiments as well as yield

gap analysis using crop simulation models andresearchers managed trials on farmers fieldshave demonstrated that crop yields in rainfedareas can go up as high as 5 t/ha under semi-aridtropical Indian conditions. Large yield gaps existin a number of rainfed crops such as maize,sorghum, pigeonpea, groundnut, soybean, pearl

millet, chickpea, wheat and paddy in differentcountries of Asia and Africa.

Given such potential, the assessmentconcluded that yields could easily be doubled inrainfed areas of Asia and quadrupled in Africa,provided the adoption of available improvedsoil, water, crop and pest management optionson farmers fields is enhanced. It stronglyfavours abolishing the artificial divide betweendryland and irrigated systems with its bias

towards irrigation management.Written by reputed specialists in rainfed agri-

culture, representing three premier internationalinstitutes ICRISAT, the Stockholm EnvironmentInstitute (SEI) and the International Center forAgricultural Research in the Dry Areas (ICARDA),the book is a synthesis of the voluminous researchundertaken by the CA team. It covers all aspectsof rainfed agriculture, starting with its potential,current status, rainwater harvesting and supple-

mentary irrigation to policies, approaches, insti-tutions for upscaling, and impacts of integratedwater management programmes in rainfed areas.

Rainfed Agriculture: Unlocking the Potentialshows that the road to realizing a second GreenRevolution lies in greening drylands to achieveglobal food security, reduce poverty and protectthe environment. It is a very valuable resourcematerial for researchers, policy makers, develop-ment investors, development workers and

students.

William D. Dar

Director GeneralICRISAT


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Preface

The world is facing multiple challenges in the21st century and those important challenges forhumanity are poverty, food security, scarcity ofwater and, most importantly, new and complexchallenges emerging due to global warming andclimate change. Ever-increasing human popu-

lation, changing lifestyle and dietary habits dueto increased incomes, competing demand for thenatural resources such as land and water,diversion of food crops for biofuel productionand stagnating/lower growth rates for foodproduction in the world are some of the mainreasons for the food shortages and increasingfood prices. The Comprehensive Assessment(CA) of Water for Food and Water for Lifeundertook a detailed and systematic assessment

of the current status, future demands of foodrequirement and necessary water required toproduce the same. The CA identified ten majorquestions at the beginning to be addressedholistically, covering different sectors of foodproduction. A large number of institutions andscientists, policy makers and developmentworkers worked together for 5 years andcollected evidence and data, analysed criticallyand ran scenarios to address the most importantissue of achieving food security with the loomingwater scarcity. These studies have culminated ina number of recommendations for each sector offood production. The CA has reached theconclusion that it is possible to meet the currentas well as future food demands with the availablewater resources; however, it calls for new and

innovative approaches (technical, institutional,policies, attitudes and habits) for food productionand water management strategies, as the busi-ness as usual scenario will not meet the demand.

Rainfed agriculture plays, and will continueto play, an important role in global food pro-

duction as 80% of agriculture is rainfed andcontributes about 58% to the global food basket.In addition rainfed areas are also the hot-spots ofpoverty, malnutrition, water scarcity, severe landdegradation, and poor physical and financialinfrastructure. Under the CA, issues of rainfedagriculture were analysed in depth by a group ofspecialized institutions led by the InternationalCrops Research Institute for the Semi-AridTropics (ICRISAT), Patancheru, India, and

the Stockholm Environment Institute (SEI),Sweden. The results of 2 years comprehensivestudy by a large number of scientists working inrainfed agriculture are put together in thisvolume. The major finding of the CA of rainfedagriculture for food security is that the vastuntapped potential of rainfed agriculture needsto be tapped as the current farmers crop yieldsare lower by two- to fivefold than the potential,based on the clear documented evidence. TheCA calls for upgrading of rainfed agricultureby adopting a new paradigm where artificialboundaries between rainfed and irrigated agri-culture need to be discarded: science-baseddevelopment by adopting a small catchment/watershed approach with integrated genetic andnatural resource management (IGNRM), with

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xiv Preface

community participation and more investmentsin rainfed areas. Innovative mechanisms toshare the knowledge with the farmers and other

stakeholders are very much needed as thetraditional extension mechanisms worldwide,particularly in developing countries in Asia andAfrica, are not effective. By upgrading rainfedagriculture in dryland areas in the semi-arid andhumid tropics, efficiency of green water for foodproduction can be substantially increased andpressure on blue water for food production canbe reduced. Green water for food production isalmost three times more than blue water (5000

km3versus 1800 km3) globally.This book, Rainfed Agriculture: Unlocking

the Potential, opens up vistas of new, untappedopportunities to meet the challenges of en-hancing food production with limited waterresources. The small catchment/watershedmanagement approach calls for new man-agement tools and attitudes as communitiesplay a critical role in conservation and en-hancement of precious natural resources for

sustainable development. Most importantly, thepolicy makers and development investors willfind that these new opportunities are moreproductive not only in terms of economicparameters but also in terms of addressingissues of equity, gender, inclusive growth and,most importantly, for building resilience of the

natural resources and communities to meet thefuture challenges including those due toglobalization and climate change.

The book is organized into 14 chaptersaddressing the issues, starting with the past trendsand future prospects, followed by zooming inon the global hotspots of rainfed agriculture,water resource implications of upgrading rain-fed agriculture, tectonicsclimate-linked naturalsoil degradation and its impact on rainfed agri-culture, determinants of crop growth and yield ina changing climate, yield gap analysis, canrainfed agriculture feed the world? scenario

analysis, crop water productivity enhancementthrough genetic enhancement, water harvestingand supplemental irrigation in arid and SATareas, integrated farm management practices,challenges of adoption and adaptation in small-holder agriculture and scaling-out communitywatershed management benefits in rainfed areas.This valuable resource book, with contributionsfrom renowned scientists, will be useful for thespectrum of stakeholders including students,

development investors, development agents, re-searchers and policy makers alike.

Suhas P. Wani,

Johan Rockstrm

andTheib Oweis


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xv

Acknowledgements

Peter Hobbs, Cornell University, USAMalin, Falkenmark, Stockholm International Water Institute (SIWI), Sweden

J.S. Samra,National Rainfed Area Authority, IndiaJan Lundquist, Stockholm International Water Institute (SIWI), SwedenA.V.R. Kesava Rao,International Crops Research Institute for the Semi-Arid Tropics, IndiaSteduto Pasquel, Water Development and Management Unit (NRLW), Food and Agriculture

Organization of the United Nations (FAO), Rome, ItalyJennie Barron, Stockholm Environment Institute (SEI), UKA.K. Singh,Indian Agricultural Research Institute (IARI), IndiaR.B. Deshmukh,Mahatma Phule Krishi Vidyapeeth, IndiaP. Pathak,International Crops Research Institute for the Semi-Arid Tropics, IndiaPiara Singh,International Crops Research Institute for the Semi-Arid Tropics, IndiaMohammed Osman, Central Research Institute for Dryland Agriculture, IndiaA.K. Misra,National Research Centre for Women in Agriculture, IndiaP.K. Joshi,National Centre for Agricultural Economics and Policy Research, IndiaK. Palanisami, Centre for Agriculture & Rural Development Studies (CARDS), IndiaV. Ratna Reddy, Centre for Economics and Soil Studies (CESS), IndiaK.V. Raju,Institute For Social & Economic Change, IndiaP.G. Chengappa, University of Agricultural Sciences, IndiaK.L. Sahrawat,International Crops Research Institute for the Semi-Arid Tropics, India


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1 Rainfed Agriculture Past Trendsand Future Prospects

S.P. Wani,1* T.K. Sreedevi,1** J. Rockstrm2*** and Y.S. Ramakrishna3****1International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru,

Andhra Pradesh, India; 2Stockholm Environment Institute (SEI),Stockholm, Sweden; 3Central Research Institute for Dryland

Agriculture (CRIDA), Hyderabad, Andhra Pradesh, India;emails:*[email protected]; **[email protected]; ***[email protected];

****[email protected]

Introduction

The agricultural productivity has seen a rapidgrowth since the late 1950s due to new crop vari-eties, fertilizer use and expansion in irrigated agri-culture. The world food production outstrippedthe population growth. However, there areregions of food insecurity. Of the 6.5 billion popu-lation today, about 850 million people face foodinsecurity. About 60% of them live in South Asiaand sub-Saharan Africa. Food and crop demandis estimated to double in the next 50 years.

According to a Comprehensive Assessment, it ispossible to produce food but it is probable thattodays food production and environmentaltrends, if continued, will lead to crises in manyparts of the world (Molden, 2007). The assess-ment has also indicated that the worlds availableland and water resources can satisfy futuredemands by taking the following steps:

Investing to increase production in rainfedagriculture (rainfed scenario).

Investing in irrigation (irrigation scenario). Conducting agricultural trade within and

between countries (trade scenario). Reducing gross food demand by influencing

diets, and reducing postharvest losses, includ-ing industrial and household waste.

Rainfed Agriculture

The importance of rainfed agriculture variesregionally but produces most food for poorcommunities in developing countries. In sub-Saharan Africa more than 95% of the farmedland is rainfed, while the corresponding figurefor Latin America is almost 90%, for South Asiaabout 60%, for East Asia 65% and for the NearEast and North Africa 75% (FAOSTAT, 2005).Most countries in the world depend primarily onrainfed agriculture for their grain food. Despite

large strides made in improving productivity andenvironmental conditions in many developingcountries, a great number of poor families inAfrica and Asia still face poverty, hunger, foodinsecurity and malnutrition where rainfed agri-culture is the main agricultural activity. Theseproblems are exacerbated by adverse biophysi-cal growing conditions and the poor socio-economic infrastructure in many areas in thesemi-arid tropics (SAT). The SAT is the home to

38% of the developing countries poor, 75% ofwhom live in rural areas. Over 45% of theworlds hungry and more than 70% of itsmalnourished children live in the SAT.

Even with growing urbanization, globalizationand better governance in Africa and Asia, hunger,poverty and vulnerability of livelihoods to natural

CAB International 2009. Rainfed Agriculture: Unlocking the Potential(eds S.P. Wani et al.) 1


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and other disasters will continue to be greatest inthe rural SAT. These challenges are complicatedby climatic variability, the risk of climate change,

population growth, health pandemics (AIDS,malaria), degrading natural resource base, poorinfrastructure and changing patterns of demandand production (Ryan and Spencer, 2001). Themajority of poor in developing countries live inrural areas; their livelihoods depend on agricul-ture and overexploitation of the natural resourcebase, pushing them into a downward spiral ofpoverty. The importance of rainfed sources offood weighs disproportionately on women, given

that approximately 70% of the worlds poor arewomen (WHO, 2000). Agriculture plays a keyrole for economic development (World Bank,2005) and poverty reduction (Irz and Roe, 2000),with evidence indicating that every 1% increasein agricultural yields translates to a 0.61.2%decrease in the percentage of absolute poor(Thirtle et al., 2002). On average for sub-SaharanAfrica, agriculture accounts for 35% of grossdomestic product (GDP) and employs 70% of the

population (World Bank, 2000), while more than95% of the agricultural area is rainfed (FAOSTAT,2005), as elaborated in Box 1.1. Agriculture willcontinue to be the backbone of economies inAfrica and South Asia in the foreseeable future.As most of the SAT poor are farmers and landlesslabourers, strategies for reducing poverty, hungerand malnutrition should be driven primarily bythe needs of the rural poor, and should aim tobuild and diversify their livelihood sources.

Substantial gains in land, water and labourproductivity as well as better management ofnatural resources are essential to reverse thedownward spiral of poverty and environmentaldegradation. Apart from the problems of equity,poverty and sustainability and hence, the needfor greater investment in SAT areas studies have

shown that research and development (R&D)investments in less-favoured semi-arid environ-ments could provide high marginal payoffs in

terms of generating new sources of economicgrowth. Renewed effort and innovative R&Dstrategies are needed to address these challenges,such as integrated natural resource management(INRM), which has been evolving within the 15international agricultural research centres (IARC)of the Consultative Group for InternationalAgricultural Research (CGIAR). The basic role ofthe 15 IARCs is to develop innovations forimproving agricultural productivity and natural

resource management (NRM) for addressing theproblems of poverty, food insecurity and environ-mental degradation in developing countries. Thiseffort has generated multiple and sizeable bene-fits (welfare, equity, environmental) (Kassam etal., 2004). But much remains to be done in sub-Saharan Africa and less-favoured areas of SouthAsia.

Rainfed agriculture and water stress

There is a correlation between poverty, hungerand water stress (Falkenmark, 1986). The UNMillennium Development Project has identifiedthe hot spot countries in the world suffering fromthe largest prevalence of malnourishment. Thesecountries coincide closely with those located inthe semi-arid and dry subhumid hydroclimates inthe world (Fig. 1.1), i.e. savannahs and steppe

ecosystems, where rainfed agriculture is thedominating source of food and where waterconstitutes a key limiting factor to crop growth(SEI, 2005). Of the 850 million undernourishedpeople in the world, essentially all live in poor,developing countries, which predominantly arelocated in tropical regions (UNSTAT, 2005).

2 S.P. Wani et al.

Box 1.1. Agricultural growth: an underlying factor to economic growth (after van Koppen et al., 2005).

Agriculture, the sector in which a large majority of the African poor make their living, is the engine ofoverall economic growth and, therefore, broad-based poverty reduction (Johnston and Mellor, 1961;World Bank, 1982; IFAD, 2001; DFID, 2002; Koning, 2002). This conclusion is based on analysis of thehistorical development paths of countries worldwide, and recent international reports have re-affirmedthis position (e.g. Inter Academy Council, 2004; Commission for Africa, 2005; UN Millennium Project,2005). Higher farm yields enhanced producer incomes, in cash and in kind, and created demand for agri-cultural labour. Thus, agricultural growth typically preceded economic growth in high-income countriesand recent growth in the Asian Tigers such as Thailand, Malaysia, Indonesia, Vietnam and parts of China.


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Crop yields in rainfed areas

Since the late 1960s, agricultural land use hasexpanded by 2025%, which has contributedto approximately 30% of the overall grainproduction growth during the period (FAO,2002; Ramankutty et al., 2002). The remainingyield outputs originated from intensification

through yield increases per unit land area.However, the regional variation is large, as isthe difference between irrigated and rainfedagriculture. In developing countries rainfedgrain yields are on average 1.5 t/ha, comparedwith 3.1 t/ha for irrigated yields (Rosegrant etal., 2002), and increase in production fromrainfed agriculture has mainly originated fromland expansion.

Trends are clearly different for different

regions. With 99% rainfed production of maincereals such as maize, millet and sorghum, thecultivated cereal area in sub-Saharan Africa hasdoubled since 1960 while the yield per unit ofland has been nearly stagnant for these staplecrops (FAOSTAT, 2005). In South Asia, therehas been a major shift away from moredrought-tolerant, low-yielding crops such assorghum and millet, while wheat and maize has

approximately doubled in area since 1961(FAOSTAT, 2005). During the same period, theyield per unit of land for maize and wheat hasmore than doubled (Fig. 1.2). For predomi-nantly rainfed systems, maize crops per unit ofland have nearly tripled and wheat more thandoubled during the same time period.

Rainfed maize yield differs substantially

between regions (Fig. 1.2a). In Latin America(including the Caribbean) it exceeds 3 t/ha, whilein South Asia it is around 2 t/ha and in sub-Saharan Africa it only just exceeds 1 t/ha. Thiscan be compared with maize yields in the USA orsouthern Europe, which normally amount toapproximately 710 t/ha (most maize in theseregions is irrigated). The average regional yieldper unit of land for wheat in Latin America(including the Caribbean) and South Asia is simi-

lar to the average yield output of 2.52.7 t/ha inNorth America (Fig. 1.2b). In comparison, wheatyield in Western Europe is approximately twiceas large (5 t/ha), while in sub-Saharan Africa itremains below 2 t/ha. In view of the historicregional difference in development of yields,there appears to exist a significant potential forraised yields in rainfed agriculture, particularly insub-Saharan Africa and South Asia.

Rainfed Agriculture 3

Fig. 1.1. The prevalence of undernourishment in developing countries (as percentage of population20012002; UNSTAT, 2005), together with the distribution of semi-arid and dry subhumid hydroclimates inthe world, i.e. savannah and steppe agroecosystems. These regions are dominated by sedentary farmingsubject to the worlds highest rainfall variability and occurrence of dry spells and droughts.


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Rainfed Agriculture a LargeUntapped Potential

In several regions of the world rainfed agricul-ture generates among the worlds highest

yields. These are predominantly temperateregions, with relatively reliable rainfall andinherently productive soils. Even in tropicalregions, particularly in the subhumid andhumid zones, agricultural yields in commercialrainfed agriculture exceed 56 t/ha (Rockstrmand Falkenmark, 2000; Wani et al., 2003a,b).At the same time, the dry subhumid and semi-arid regions have experienced the lowest yields

and the weakest yield improvements per unit ofland. Here, yields oscillate between 0.5 and 2t/ha, with an average of 1 t/ha in sub-SaharanAfrica, and 11.5 t/ha in South Asia, andcentral and west Asia and North Africa

(CWANA) for rainfed agriculture (Rockstrmand Falkenmark, 2000; Wani et al., 2003a,b).Yield gap analyses carried out by

Comprehensive Assessment for major rainfedcrops in semi-arid regions in Asia and Africaand rainfed wheat in WANA reveal large yieldgaps, with farmers yields being a factor of twoto four times lower than achievable yields formajor rainfed crops. Detailed yield gap analysis

4 S.P. Wani et al.

0

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South AsiaEuropeNorth America

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Gr a i n

y i e l d (

t /ha )

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Fig. 1.2. Grain yield of predominantly rainfed maize (a) and wheat (b) for different regions during19612000 (Source: FAOSTAT, 2005).


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for major rainfed crops in different parts of theworld is discussed (see Chapter 6, this volume).Figure 1.3 illustrates examples of observed yield

gaps in various countries in Africa, Asia and theMiddle East. In countries in eastern andSouthern Africa the yield gap is very large.Similarly, in many countries in west Asia, farm-ers yields are less than 30% of achievableyields, while in some Asian countries the figureis closer to 50%. Historic trends present a grow-ing yield gap between farmers practices andfarming systems that benefit from managementadvances (Wani et al., 2003b).

Constraints in Rainfed Agriculture Areas

An insight into the inventories of naturalresources in rainfed regions shows a grim pictureof water scarcity, fragile environments, droughtand land degradation due to soil erosion bywind and water, low rainwater use efficiency(3545%), high population pressure, poverty,

low investments in water use efficiency (WUE)measures, poor infrastructure and inappropriatepolicies (Wani et al., 2003b,c; Rockstrm et al.,2007). Drought and land degradation are inter-linked in a cause and effect relationship, and thetwo combined are the main causes of poverty in

farm households. This unholy nexus betweendrought, poverty and land degradation has to bebroken to meet the Millennium Development

Goal of halving the number of food-insecurepoor by 2015. These rainfed areas are prone tosevere land degradation. Reduction in theproducing capacity of land due to wind and watererosion of soil, loss of soil humus, depletion of soilnutrients, secondary salinization, diminution anddeterioration of vegetation cover as well as loss ofbiodiversity is referred to as land degradation. Aglobal assessment of the extent and form of landdegradation showed that 57% of the total area of

drylands occurring in two major Asian countries,namely China (178.9 million ha) and India(108.6 million ha), are degraded (UNEP, 1997).

The root cause of land degradation is poorland use. Land degradation represents a dimin-ished ability of ecosystems or landscapes tosupport the functions or services required forsustaining livelihoods. Over a period of time,continuing agricultural production, particularlyin marginal and fragile lands, results in degrada-

tion of the natural resource base, with increasingimpact on water resources. The followingnatural resources degradation and the relation-ship between major forms of soil degradationand water resources (Bossio et al., 2007) requireattention:


Fig. 1.3. Examples of observed yield gap (for major grains) between farmers yields and achievable yields(100% denotes achievable yield level, and columns actual observed yield levels) (Source: derived fromRockstrm et al., 2007).


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Loss of organic matter and physical degrada-tion of soil: soil organic matter is integral tomanaging water cycles in ecosystems.

Depleted levels of organic matter havesignificant negative impacts on infiltrationand porosity, local and regional water cycles,water productivity, plant productivity, theresilience of agroecosystems and globalcarbon cycles.

Nutrient depletion and chemical degradationof soil: pervasive nutrient depletion in agri-cultural soils is a primary cause of decreas-ing yields, low on-site water productivity and

off-site water pollution. Salinity, sodicity andwaterlogging threaten large areas of theworlds most productive land and pollutegroundwater.

Soil erosion and sedimentation: acceleratedon-farm soil erosion leads to substantialyield losses and contributes to downstreamsedimentation and degradation of waterbodies, a major cause of investment failurein water and irrigation infrastructure.

Water scarcity and pollution: globally, agricul-ture is the main consumer of water, and waterscarcity is a significant problem for farmers inAfrica, Asia and the Near East. Agriculture isalso the major contributor to non-point-source water pollution, while urbanizationcontributes increasingly large volumes ofwastewater. Water quality problems can oftenbe as severe as those of water availability buthave yet to receive as much attention in

developing countries.

Loss of organic matter and physicaldegradation of soil

Soil organic matter is integral to managingwater cycle ecosystems. The impact of organicmatter loss is not confined to production lossbut also disturbs the water cycle. The decrease

of soil organic matter, along with the associatedfaunal activities (aggravated by the use of pesti-cides and tillage practices), favours the collapseof soil aggregates and thus the crusting and thesealing of the soil surface. The result is reducedporosity, less infiltration and more run-off.Compaction of the soil surface by heavymachinery or overgrazing, for example, cancause overland flow, even on usually perme-

able soils. Such changes increase the risk offlooding and water erosion. Higher run-offconcentrates in channels, causing rills and then

gullies. Degradation thus changes the propor-tion of water flowing along pathways withincatchments, with a tendency to promote rapidsurface overland flow (run-off) and decreasesubsurface flow. By controlling infiltration ratesand water-holding capacity, soil organic matterplays a vital function in buffering yields throughclimatic extremes and uncertainty. Significantly,it is one of the most important biophysicalelements that can be managed to improve

resilience. Soil organic matter, furthermore,holds about 40% of the overall terrestrialcarbon pool twice the amount contained inthe atmosphere. Poor agricultural practices arethus a significant source of carbon emissionsand contribute to climate change.

Nutrient depletion and chemicaldegradation of soil

Globally, only half of the nutrients that cropstake from the soil are replaced. This depletionof soil nutrients often leads to fertility levels thatlimit production and severely reduce waterproductivity. Shorter fallow periods do notcompensate for losses in soil organic matter andnutrients, leading to the mining of soil nutrients.In many African, Asian and Latin Americancountries, the nutrient depletion of agricultural

soils is so high that current agricultural land useis not sustainable. Nutrient depletion is nowconsidered the chief biophysical factor limitingsmall-scale production in Africa (Drechsel et al.,2004). Recent characterization of 4000 farmersfields in different states across India revealed awidespread (80100% fields) deficiency of zinc,boron and sulfur in addition to known de-ficiencies of macronutrients such as nitrogenand phosphorus (Sahrawat et al., 2007). Such

multi-nutrient deficiencies are largely due todiversion of organic manures to irrigated, high-value crops and more reliance on chemicalfertilizers supplying macronutrients in pure formover a long period. Other important forms ofchemical degradation are the depletion of tracemetals such as zinc and iron, causing productiv-ity declines and affecting human nutrition,acidification and salinization.

6 S.P. Wani et al.


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Soil erosion and sedimentation

Accelerated erosion, resulting in loss of nutrient-

rich, fertile topsoil, occurs nearly everywherewhere agriculture is practised and is irreversible.The torrential character of the seasonal rainfallcreates high risk for the cultivated lands. InIndia, alone, some 150 million ha are affectedby water erosion and 18 million ha by winderosion. Soil loss ranged from 0.01 to 4.30 t/hafrom sandy loam soils of Bundi district,Rajasthan, India, with the average annual rain-fall of 760 mm as monitored during rainfall

events over 4 years in a case study (Pathak etal., 2006). Thus, erosion leaves behind animpoverished soil on the one hand and siltationof reservoirs and tanks on the other. The esti-mated nutrient losses in Thailand are indicatedin Table 1.1 (Narongsak et al., 2003). Soilerosion reduces crop yields by removing nu-trients and organic matter. Erosion also inter-feres with soilwater relationships: the depth ofsoil is reduced, diminishing water storage capac-

ity and damaging soil structure, thus reducingsoil porosity. Downstream, the main impact ofsoil erosion is sedimentation, a major form ofhuman-induced water pollution.

Water scarcity and pollution

Water scarcity is a significant problem for farm-ers in Africa, Asia and the Near East, where

8090% of water withdrawals are used for agri-culture (FAO/IIASA, 2000; Rosegrant et al.,2002). Water, a finite resource, the very basis oflife and the single most important feature of ourplanet, is the most threatened natural resourceat the present time. Water is the most importantdriver for four of the Millennium DevelopmentGoals, as shown in Fig. 1.4. In the context ofthese four goals, the contribution of water

resources management through direct interven-tions is suggested to achieve the milestones by2015. However, in many SAT situations water

quantity per se is not the limiting factor forincreased productivity but its management andefficient use are the main yield determinants.Instead, the major water-related challenge forrainfed agriculture in semi-arid and dry sub-humid regions is to deal with the extreme vari-ability in rainfall, characterized by few rainfallevents, high-intensity storms, and high fre-quency of dry spells and droughts. For example,in Kurnool district, one of the most drought-

prone districts in Andhra Pradesh, India, there isa large variation in rainfall return years. Thenormal annual rainfall is about 660 mm, ofwhich about 90% is received in the 6-monthperiod of June to November. During a periodof 55 years, normal rainfall (19 to +19% inreference to normal rainfall) was received in30 years, excess rainfall (>20% over normalrainfall) in 11 years and deficit rainfall (20 to59% of normal rainfall) in 14 years. It is there-

fore critical to understand the impact of hydro-climatic conditions and water management onyields in rainfed agriculture. Key constraints torainwater productivity evidently differ greatlyacross the wide range of rainfall zones. In thearid regions, it is the absolute amount of water(so-called absolute water scarcity) that consti-tutes the major limiting factor in agriculture. Inthe semi-arid and dry subhumid tropical regionson the other hand, seasonal rainfall is generally

adequate to significantly improve yields. Here,managing extreme rainfall variability in time andspace is the largest water challenge. Only in thedry semi-arid and arid zones, considering meanrainfall, is absolute water stress common. In thewetter part of the semi-arid zone, and into thedry subhumid zone, rainfall generally exceedscrop water needs.

Absolute water scarcity is thus rarely themajor problem for rainfed agriculture. Still

water scarcity is a key reason behind low agri-cultural productivity. To identify managementoptions to upgrade rainfed agriculture it istherefore essential to assess different types ofwater stress in food production. Of particularimportance is to distinguish between climate-and human-induced water stress, and thedistinction between droughts and dry spells(Table 1.2). In semi-arid and dry subhumid


Table 1.1. Nutrient loss (t/year) in different regionsof Thailand.

Region Nitrogen Phosphorus Potassium

Northern 38,288 4,467 75,588

North-eastern 18,896 1,212 91,644

Eastern 17,890 1,074 30,860

Southern 17,310 1,453 13,254

Source: Land Development Department, Thailand.


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agroecosystems, rainfall variability generatesdry spells (short periods of water stress duringgrowth) almost every rainy season (Barron etal., 2003), compared with meteorologicaldroughts, which occur on average once every

decade in moist semi-arid regions and up totwice every decade in dry semi-arid regions.When there is not enough rainfall to generate acrop, meteorological droughts result incomplete crop failure. Such droughts cannot bebridged through agricultural water manage-ment, and instead social coping strategies arerequired, such as grain banks, relief food, localfood storage and livestock sales. Dry spells, on

the other hand, are manageable, i.e. invest-ments in water management can bridge dryspells, which generally are 24 weeks of norainfall during critical stages of plant growth(Box 1.2).

Even in regions with low variable rainfall,only a fraction actually forms soil moisture, i.e.green water resource, in farmers fields. Ingeneral, only 7080% of the rainfall is availableto the plants as soil moisture, and on poorlymanaged land the fraction of plant-availablewater can be as low as 4050% (Falkenmarkand Rockstrm, 2004). This leads to agricul-tural dry spells and droughts, which are not

8 S.P. Wani et al.

Fig. 1.4. Water is an important driver for achieving the Millennium Development Goals.

Table 1.2. Types of water stress and underlying causes in semi-arid and dry subhumid tropicalenvironmentsa.

Types of water stress Dry spell Drought

Meteorological Occurrence: 2 out of 3 years Occurrence: 1 out of 10 yearsImpact: yield reduction Impact: complete crop failureCause: rainfall deficit of 25-week Cause: seasonal rainfall below

periods during crop growth minimum seasonal plant waterrequirement

Agricultural (human Occurrence: >2 out of 3 years Occurrence: >1 out of 10 yearsinduced) Impact: yield reduction or Impact: complete crop failure

complete crop failure Cause: poor rainfall partitioning leadsCause: low plant water availability to seasonal soil moisture deficit to

and poor plant water uptake produce harvestcapacity

a Source: Falkenmark and Rockstrm (2004).


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caused primarily by rainfall deficiencies butinstead are due to management-related prob-lems with the on-farm water balance. Theoccurrence of agricultural droughts and dryspells are thus not only an indicator of pooragricultural water management but also a signof a large opportunity to improve yields, asthese droughts and dry spells are to a largedegree manageable.

In addition, imbalanced use of nutrients inagriculture by the farmers results in mining ofsoil nutrients. Recent studies in India revealedthat 80100% of the farmers fields were found

to be critically deficient in zinc, boron andsulfur in addition to nitrogen and organiccarbon (Rego et al., 2005; Wani et al., 2006a).Overall the constraints of rainfed productionare many (Box 1.3). If the current productionpractices are continued, developing countries inAsia and Africa will face a serious food shortagein the very near future. The major constraintsfor low on-farm yields and large yield gap are:

Inappropriate NRM practices followed bythe farmers.

Lack of knowledge. Low investments in rainfed agriculture. Lack of policy support and infrastructure

including markets and credit. Traditional cultivars. Low use of fertilizers. Low rainwater use efficiency. Pests and diseases. Compartmental approach.

Potential of Rainfed Agriculture

In several regions of the world rainfed agricul-ture generates the worlds highest yields. Theseare predominantly temperate regions, with rela-tively reliable rainfall and inherently productivesoils. Even in tropical regions, particularly in thesubhumid and humid zones, agricultural yieldsin commercial rainfed agriculture exceed 56t/ha (Rockstrm and Falkenmark, 2000; Wani etal., 2003a,b; Rockstrm et al., 2007). Evidence

from a long-term experiment at the InternationalCrops Research Institute for the Semi-Arid


Box 1.2. Dry spell occurrence and yield implications in savannah agroecosystems.

Barron et al. (2003) studied dry spell occurrence in semi-arid locations in Kenya and Tanzania and found

that meteorological dry spells of >10 days occurred in 70% of seasons during the flowering stage of thecrop (maize), which is very sensitive to water stress. Regions with similar seasonal rainfall can experiencedifferent dry spell occurrence. In the semi-arid Nandavaram watershed, Andhra Pradesh, India, withapproximately 650 mm of rainfall, there is a high risk of dry spell occurrence (>40% risk) during the vege-tative and flowering stages of the crop, compared with semi-arid Xiaoxingcun, Southern China, receivingsimilar rainfall but with only a 20% risk of early season dry spells (Kesava Rao et al., 2007).

Box 1.3. Constraints identified by the stakeholders in Shekta watershed, Maharashtra, India.

Land degradation because of felling trees, shrubs and free grazing had intensified and added to theproblems of excessive run-off and soil erosion.

Due to irregular and insufficient rainfall, there was severe scarcity of drinking water throughout the year. During summer, wells dried up frequently and the water table declined, leading to high intensity of

water requirement in a short period and thus influencing crop failures, drought, etc.

Livestock production in the village is limited mainly to goats, sheep, indigenous cows, buffaloes andbullocks but there is not much emphasis on breed improvement, animal nutrition and health forimproving productivity.

The socio-economic status of the people is very low and the education of children, especially female,is low although the village has set up a primary school (up to 9 years of age) in the village itself.

The problem of market access and price fluctuations compounds the problems of inappropriate pricesfor the farm produce and decision making.

At initial stages of watershed development the decision of the community to ban free grazing disturbedthe livelihood of small farmers, shepherds and families owning small ruminants.


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Tropics (ICRISAT), Patancheru, India, since1976 demonstrated the virtuous cycle of persis-tent yield increase through improved land, water

and nutrient management in rainfed agriculture.Improved systems of sorghum/pigeonpea inter-crops produced higher mean grain yields(5.1 t/ha) compared with 1.1 t/ha, the averageyield of sole sorghum in the traditional (farm-ers) post-rainy system, where crops are grownon stored soil moisture (Fig. 1.5). The annualgain in grain yield in the improved system was82 kg/ha/year compared with 23 kg/ha/year inthe traditional system. The large yield gap be-

tween attainable yield and farmers practice aswell as between the attainable yield of 5.1 t/haand potential yield of 7 t/ha shows that a largepotential of rainfed agriculture remains to betapped. Moreover, the improved managementsystem is still continuing to provide an increasein productivity as well as improving soil quality(physical, chemical and biological parameters)along with increased carbon sequestration of330 kg C/ha/year (Wani et al., 2003a). Yield gap

analyses, undertaken for the ComprehensiveAssessment of Water for Food and Water forLife, for major rainfed crops in semi-arid regionsin Asia (Fig. 1.6) and Africa and rainfed wheatin WANA reveal large yield gaps, with farmersyields being a factor of two to four lower thanachievable yields for major rainfed crops grownin Asia and Africa (Rockstrm et al., 2007). At

the same time, the dry subhumid and semi-aridregions experience the lowest yields and thelowest productivity improvements. Here, yields

oscillate between 0.5 and 2 t/ha, with an aver-age of 1 t/ha, in sub-Saharan Africa, and 11.5t/ha in SAT Asia, Central Asia and WANA(Rockstrm and Falkenmark 2000; Wani et al.,2003a,b; Rockstrm et al., 2007).

Farmers yields continue to be very lowcompared with the experimental yields (attain-able yields) as well as simulated crop yields(potential yields), resulting in a very significantyield gap between actual and attainable rainfed

yields. The difference is largely explained byinappropriate soil, water and crop managementoptions used at the farm level, combined withpersistent land degradation.

The vast potential of rainfed agricultureneeds to be unlocked through knowledge-based management of natural resources forincreasing productivity and income to achievefood security in the developing world. Soil andwater management play a very critical role in

increasing agricultural productivity in rainfedareas in the fragile SAT systems.

New Paradigm in Rainfed Agriculture

Current rainfed agriculture cannot sustain theeconomic growth and food security needed.

10 S.P. Wani et al.

Fig. 1.5. Three-year moving average of sorghum and pigeonpea grain yield under improved and traditionalmanagement in a deep vertisol catchment at Patancheru, India.


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There is an urgent need to develop a new para-digm for soil and water management. We needto have a holistic approach based on converg-ing all the necessary aspects of natural resourceconservation, their efficient use, productionfunctions and income-enhancement avenuesthrough value-chain and enabling policies andmuch-needed investments in rainfed areas.

Integrated genetic and natural resourcemanagement

Traditionally, crop improvement and NRM wereseen as distinct but complementary disciplines.ICRISAT is deliberately blurring these boundariesto create the new paradigm of IGNRM (integratedgenetic and natural resource management)(Twomlow et al., 2006). Improved varieties andimproved resource management are two sides of

the same coin. Most farming problems requireintegrated solutions, with genetic, management-related and socio-economic components. Inessence, plant breeders and NRM scientists mustintegrate their work with that of private- andpublic-sector change agents to develop flexiblecropping systems, which can respond to rapidchanges in market opportunities and climaticconditions. It is time to stop debate on genetic

enhancement or NRM and adopt the IGNRMapproach converging genetic, NRM, social andinstitutional aspects with market linkages. Thesystems approach looks at various components ofthe rural economy traditional food grains, newpotential cash crops, livestock and fodderproduction, as well as socio-economic factorssuch as alternative sources of employment andincome. Crucially the IGNRM approach is partici-patory, with farmers closely involved in tech-

nology development, testing and dissemination.Technologies must match not only the cropor livestock enterprise and the biophysical en-vironment but also the market and investmentenvironment, including seed availability. Plantbreeders and NRM scientists must integratetheir work with change agents (both public andprivate sector), and work with target groups todevelop flexible cropping systems that canrespond to changes in market opportunities.

Rather than pursuing a single correct answer,we need to look for multiple solutions tailoredto the requirements of contrasting environ-ments and diverse sets of households. Theseinclude small and marginal farmers, female-headed households, HIV/AIDS-affected house-holds, those lacking draft power, farmers withpoor market access as well as households withgood market access and better commercial


0

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Soy

bean

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Khari

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hum

Ra

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hum

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illet

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Chickpea

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ize

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flower

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bean

Groun

dnu

t

Ma

ize

Ma

ize

India NE Thailand Vietnam Kenya

Rainfed potential yield

Farmers' yield

Yield(t/ha)

Fig. 1.6. Yield gap of important rainfed crops in different countries (Source: Rockstrm et al., 2007).


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production opportunities. In the rainfed areas,to improve livelihoods the approach has to bea business one through marketable surplus pro-

duction through diversified farming systemswith necessary market linkages and institutionalarrangements.

ICRISATs studies in Africa and Asia haveidentified several key constraints to more wide-spread technology adoption (Ryan and Spencer,2001). Other institutes have independentlyreached similar conclusions for other agroeco-systems. So there is general agreement on thekey challenges before us. These are:

Lack of a market-oriented smallholder pro-duction system where research is market-led,demand-driven and follows the commoditychain approach to address limiting con-straints along the value chain. For example,ICRISATs work on community watershedsfor improving livelihoods in Asia and devel-oping groundnut markets in Malawi aims toaddress this issue.

Poor researchextensionfarmer linkages,which limit transfer and adoption of technol-ogy. For example, ICRISATs work onFarmer Field Schools in Africa and theconsortium approach to integrated manage-ment of community watersheds in Asia aimsto strengthen these linkages.

Need for policies and strategies on soil,water and biodiversity to offset the high rateof natural resource degradation. These

issues are central to ICRISATs consortiumapproach to integrated community water-shed management.

Need to focus research on soil fertility im-provement, soil and water management,development of irrigation, promotion of inte-grated livestockwildlifecrop systems anddevelopment of drought-mitigation strate-gies. These issues are addressed by severalICRISAT programmes, e.g. low-input soil

fertility approaches in Africa; micronutrientresearch in Asia, and the Sahelian Eco-Farm. Need to strengthen capacities of institutions

and farmers organizations to support inputand output marketing and agricultural pro-duction systems. Such capacity building is aprimary goal of the Soil Water ManagementNetwork (SWMnet) of ASARECA (Associationfor Strengthening Agricultural Research in

Eastern and Central Africa) and the Easternand Central Africa Regional Sorghum andMillet Network (ECARSAM) in eastern and

central Africa, and of seed systems/germplasmimprovement networks globally.

Poor information flow and lack of communi-cation on rural development issues. Theseare being addressed by ICRISATs VASATConsortium (Virtual Academy for the Semi-Arid Tropics) globally and specificallyICRISATs Bio-economic Decision Supportwork with partners in West Africa.

Need to integrate a gender perspective in

agricultural research and training as seen inICRISATs work on HIV/AIDS ameliorationin India and Southern Africa.

Crop improvement plays an important role inaddressing each of these issues, and thusICRISAT has expanded the INRM paradigm tospecifically emphasize the role crops and geneticimprovement can play in enabling SAT agricul-ture to achieve its potential. Thus, the institute is

seeking to embrace an overall philosophy ofIGNRM. There is clear evidence from Asia andAfrica (Fig. 1.7) that the largest productivity gainsin the SAT can come from combining new vari-eties with improved crop management and NRM(Table 1.3).

A major research challenge faced in INRM isto combine the various information bitsderived from different stakeholders, and distilthese into decision rules that they can use

(Snapp and Heong, 2003). ICRISATs partici-patory research in Southern Africa demon-strated that with micro-dosing alone or incombination with available animal manuresfarmers could increase their yields by 30100%by applying as little as 10 kg of nitrogen perhectare (Dimes et al., 2005; Ncube et al., 2006;Rusike et al., 2006) (Fig. 1.8).

In much of agricultural research, the multi-disciplinary team approach has often run into

difficulties in achieving impact because of theperceived disciplinary hierarchy. The IGNRMapproach in the Community WatershedConsortium pursues integration of the knowl-edge and products of the various research disci-plines into useful extensions messages fordevelopment workers that can sustain increasedyields for a range of climatic and edaphicconditions. A similar attempt at integration

12 S.P. Wani et al.


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Table 1.3. Yield advantages observed with different crop cultivars and improved

management in Sujala watersheds of Karnataka, India during 20052006 seasons.

Yield improvement (%)

Crop Local Cultivar+IMPa HYV+FPb HYVc+IMP

Finger millet 74 2252 103123Groundnut 27 1336 4783Soybean 62 0 83

Sunflower 67 54150 152230Maize 26 70Sorghum 31

a IMP = improved management practice; b FP = farmers practice; c HYV = high-yieldingvariety.

Cropy

ield(kg/ha)

1200

1000

800

600

400

200

0

Traditional crop variety Improved crop variety Improved crop varietyand management

Fig. 1.7. Contribution of different technology components on sorghum yield, as observed in on-farm trialsin Zimbabwe (Source: Heinrich and Rusike, 2003).

Z$ return/Z$ invested

10 5 0 5 10 15

N17

N52

Proba

bilityofexceedence

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Fig. 1.8. The probability of exceeding given rates of return on nitrogen (N)-fertilizer investment on maizeproduction at 17 and 52 kg N/ha at Masvingo, Zimbabwe (Source: Dimes, 2005).


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was made for pearl millet production in Malifor a range of possible climatic scenarios(Table 1.4).

In Asia, the integrated community water-shed management approach that aims topromote income-generating and sustainablecrop and livestock production options as animportant component of improved manage-ment of watershed landscapes is a live exampleof how IGNRM led to significant benefits in apoor area (Tables 1.5 and 1.6, and Fig. 1.9)and this holistic participatory approach is trans-forming the lives of resource-poor small and

marginal farmers in the dryland areas of Asia(Wani et al., 2006a).

ICRISAT and the national agricultural re-search systems (NARS) in Asia have developedin partnership an innovative and upscalable

consortium model for managing watershedsholistically. In this approach, rainwater manage-ment is used as an entry point activity starting

with in-situ conservation of rainwater andconverging the benefits of stored rainwater intoincreased productivity by using improved crops,cultivars, suitable nutrient and pest managementpractices, and land and water management prac-tices (Table 1.6). The IGNRM approach hasenabled communities not only to harness thebenefits of watershed management but also toachieve much of the potential from improvedvarieties from a wider range of crops. The house-

holds incomes and overall productivity havemore than doubled throughout selected bench-mark sites in Asia (Fig. 1.9 and Table 1.7). Thebenefits accrue not only to landholding house-holds but also to the landless marginalized

14 S.P. Wani et al.

Table 1.4. Effect of climate variability on pearl millet crop performance and integrated genetic natural

resource management (IGNRM) options in Mali (adapted from ICRISAT, 2006).

Effects on crops andClimate parameters natural resources IGNRM options

Late onset of rains Shorter rainy season, risk that Early-maturing varieties, exploitation of

long-cycle crops will run out photoperiodism, P fertilizer at planting

of growing time

Early drought Difficult crop establishment and P fertilizer at planting, water harvesting and

need for partial or total re-sowing run-off control, delay sowing (but poor

growth due to N flush), exploit seedling

heat and drought tolerance

Mid-season drought Poor seed setting and panicle Use of pearl millet variability: differing

development, fewer productive cycles, high-tillering cultivars, optimal

tillers, reduced grain yield per root traits, etc.; water harvesting andpanicle/plant run-off control

Terminal drought Poor grain filling, fewer productive Early-maturing varieties, optimal root traits,

tillers fertilizer at planting, water harvesting

and run-off control

Excessive rainfall Downy mildew and other pests, Resistant varieties, pesticides, N fertilizer

nutrient leaching at tillering

Increased temperature Poor crop establishment (desiccation Heat-tolerance traits, crop residue

of seedlings), increased management, P fertilizer at planting (to

transpiration, faster growth increase plant vigour), large number of

seedlings per planting hill

Unpredictability of drought See above Phenotypic variability, genetically diversestress cultivars

Increased CO2 levels Faster plant growth through Promote positive effect of higher levels

increased photosynthesis, through better soil fertility management

higher transpiration

Increased occurrence of dust Seedlings buried and damaged Increase number of seedlings per planting

storms at onset of rains by sand particles hill, mulching, ridging (primary tillage)

Increased dust in the Lower radiation, reduced Increase nutrient inputs (i.e. K)

atmosphere photosynthesis


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groups through the creation of greater employ-ment opportunities. The greater resilience of

crop income in the watershed villages during thedrought year in 2002 is particularly noteworthy(Fig. 1.9). While the share of crops in householdincome declined from 44% to 12% in the non-project villages, crop income remained largelyunchanged from 36% to 37% in the watershedvillage. The loss in household income in the non-project villages was largely compensated bymigration and non-farm income which increased

from 49% in an average year to 75% during thedrought year in 2002. Much of this gain origi-

nates from improved soil fertility managementand increased availability of irrigation water andintegration of improved cultivars and croppingpatterns into the watershed systems.

While the INRM approach has made signifi-cant contributions in re-orienting research forsustainable management of natural resources,there is now a need to create clear synergies withgermplasm improvement and the income and


Table 1.5. Effect of integrated water management interventions on run-off and soil erosion in Adarsha

watershed, Andhra Pradesh, India.

Peak run-off rate

Run-off (mm) (m3/s/ha) Soil loss (t/ha)

Year Rainfall (mm) Untreated Treated Untreated Treated Untreated Treated

1999 584 16 NIa 0.013 NIa NIa NIa

2000 1161 118 65 0.235 0.230 4.17 1.46

2001 612 31 22 0.022 0.027 1.48 0.512002 464 13 Nil 0.011 Nil 0.18 Nil2003 689 76 44 0.057 0.018 3.20 1.102004 667 126 39 0.072 0.014 3.53 0.532005 899 107 66 0.016 0.014 2.82 1.20

2006 715 110 75 0.003 0.001 2.47 1.56

Mean 724 75 (10.4%) 44 (6.1%) 0.054 0.051 2.55 1.06

a Not installed.Source: Sreedevi et al. (2007).

Watershed

Non-watershed

Watershed

Non-watershed

20

02

2001

CropsLivestockNon-farm

28.9

20.2

37%

12% 13% 75%

36%

44% 7% 49%

10% 54%

15% 48%

42.5

27.6

0 4 8 12 16 20 24 28 32 36 40 44

Actual values (Rs 1000)

Fig. 1.9. Effect of integrated watershed management on flow of household net income (Source: ICRISATData Adarsha watershed, Andhra Pradesh, India).


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Table 1.6. Crop yields in Adarsha watershed, Kothapally, during 19992007.

Yield (kg/ha)

1998 base-

Crop line yield 19992000 20002001 20012002 20022003 20032004 20042005

Sole maize 1500 3250 3750 3300 3480 3920 3420

Improved intercropped 2700 2790 2800 3083 3129 2950

maize

Traditional intercropped 700 1600 1600 1800 1950 2025

maize

Improved intercropped

pigeonpea 640 940 800 720 950 680

Traditional intercropped

pigeonpea 190 200 180

Improved sole sorghum 3050 3170 2600 2425 2290 2325

Traditional sole sorghum 1070 1070 1010 940 910 952 1025

Intercropped sorghum 1770 1940 2200 2110 1980


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livelihood strategies of resource users. Thus the

IGNRM approach espoused by ICRISAT nowencompasses seed technologies and germplasmimprovement as one of the important pillars forsustainable intensification and productivityimprovement of agriculture in the SAT. Recentexperiences at ICRISAT with projects that pursuethe IGNRM approach (e.g. integrated manage-ment of community watersheds) provide opti-mism about the effectiveness and suitability ofthis approach.

Soil health: an important driver forenhancing water use efficiency

Soil health is severely affected due to landdegradation and is in need of urgent attention.ICRISATs on-farm diagnostic work in differentcommunity watersheds in different states ofIndia as well as in China, Vietnam and Thailand

showed severe mining of soils for essential plantnutrients. Exhaustive analysis showed that80100% of farmers fields are deficient notonly in total nitrogen but also in micronutrientssuch as zinc and boron and secondary nutrientssuch as sulfur (Table 1.8). In addition, soilorganic matter, an important driving force forsupporting biological activity in soil, is verymuch in short supply, particularly in tropical

countries. Management practices that augment

soil organic matter and maintain it at athreshold level are needed. Farm bunds couldbe productively used for growing nitrogen-fixing shrubs and trees to generate nitrogen-rich loppings. For example, growing Gliricidiasepium at a close spacing of 75 cm on farmbunds could provide 2830 kg nitrogen per haannually in addition to valuable organic matter.Also, large quantities of farm residues and otherorganic wastes could be converted into a valu-

able source of plant nutrients and organicmatter through vermicomposting (Wani et al.,2005). Strategic long-term catchment researchat ICRISAT has shown that legume-basedsystems, particularly with pigeonpea, couldsequester 330 kg carbon up to 150 cm depthin vertisols at Patancheru, India under rain-fed conditions (Wani et al., 2003a). Underthe National Agricultural Technology Project(NATP), ICRISAT, the National Bureau of Soil

Survey and Land Use Planning (NBSS&LUP),the Central Research Institute for DrylandAgriculture (CRIDA) and the Indian Institute ofSoil Science (IISS) have identified carbonsequestering systems for alfisols and vertisolsin India (ICRISAT, 2005). Integrated nutrientmanagement strategies go a long way inimproving soil health for enhancing WUE andincreasing farmers incomes.


Table 1.7. The effect of integrated watershed interventions on alternative sources of household income

(Rs 1000).

Crop Livestock Off-farm Household

Year Village groupa Statistics income income income income

2001 Non-project Mean 12.7 1.9 14.3 28.9

(average incomeyear) Share of total 44.0 6.6 49.5 100.0

income (%)Watershed Mean 15.4 4.4 22.7 42.5

project income

Share of total 36.2 10.4 53.4 100.0income (%)

2002 Non-project Mean income 2.5 2.7 15.0 20.2

(drought Share of total 12.2 13.3 74.5 100.0year) income (%)

Watershed Mean income 10.1 4.0 13.4 27.6project

Share of total 36.7 14.6 48.7 100.0income (%)

aThe sample size is n = 60 smallholder farmers in each group (ICRISAT data).


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Often, soil fertility is the limiting factor toincreased yields in rainfed agriculture (Stoorvogeland Smaling, 1990). Soil degradation, throughnutrient depletion and loss of organic matter,causes serious yield decline closely related towater determinants, as it affects water availabilityfor crops, due to poor rainfall infiltration, andplant water uptake, due to weak roots. Nutrientmining is a serious problem in smallholder rainfed

agriculture. In sub-Saharan Africa soil nutrientmining is particularly severe. It is estimated thatapproximately 85% of African farmland in20022004 experienced a loss of more than30 kg/ha of nutrients per year (IFDC, 2006).

In India, farmers participatory watershedmanagement trials in more than 300 villagesdemonstrated that the current subsistence farm-ing has depleted soils not only in macronutrientsbut also in micronutrients such as zinc and

boron and secondary nutrients such as sulfurbeyond the critical limits. A substantial increasein crop yields was experienced after micronu-trient amendments, and a further increase by70120% when both micronutrients and ade-quate nitrogen and phosphorus were applied,for a number of rainfed crops (maize, sorghum,mung bean, pigeonpea, chickpea, castor andgroundnut) in farmers fields (Rego et al., 2005).

Therefore, investments in soil fertility directly

improve water management. Rainwater produc-tivity (i.e. total amount of grain yield per unitof rainfall) was significantly increased in theexample above as a result of micronutrientamendment. The rainwater productivity forgrain production was increased by 70100% formaize, groundnut, mung bean, castor andsorghum by adding boron, zinc and sulfur (Regoet al., 2005). In terms of net economic returns,

rainwater productivity was substantially higherby 1.50 to 1.75 times (Rego et al., 2005).Similarly, rainwater productivity increasedsignificantly when adopting integrated land andwater management options as well as use ofimproved cultivars in semi-arid regions of India(Wani et al., 2003b).

Water resources management

For enhancing rainwater use efficiency in rainfedagriculture, the management of water alonecannot result in enhanced water productivity asthe crop yields in these areas are limited by addi-tional factors than water limitation. ICRISATsexperience in rainfed areas has clearly demon-strated that, more than water quantity per se,management of water resources is the limitation

in the SAT regions (Wani et al., 2006a).As indicated by Agarwal (2000), India wouldnot have to suffer from droughts if local waterbalances were managed better. Even duringdrought years, watershed development efforts ofimproving rainfall management have benefitedIndian farmers. For example, villages benefitingfrom watershed management projects increasedfood produce and market value by 63%compared with the non-project village even

during drought years (Wani et al., 2006b). Ananalysis in Malawi indicates that since the late1970s only a fraction of the years that havebeen politically proclaimed as drought yearsactually were years subject to meteorologicaldroughts (i.e. years where rainfall totals fallunder minimum water needs to produce foodat all) (Mwale, 2003). This is supported byGlantz (1994), who pointed out that agricultural

18 S.P. Wani et al.

Table 1.8. Percentage of farmers fields deficient in soil nutrients in different states of India.

No. offarmers OCa AvPa K S B Zn

State fields (%) (ppm) (ppm) (ppm) (ppm) (ppm)

Andhra Pradesh 1927 84 39 12 87 88 81

Karnataka 1260 58 49 18 85 76 72Madhya Pradesh 73 9 86 1 96 65 93Rajasthan 179 22 40 9 64 43 24Gujarat 82 12 60 10 46 100 82Tamil Nadu 119 57 51 24 71 89 61

Kerala 28 11 21 7 96 100 18

a OC = organic carbon; AvP = available phosphorus.


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droughts, where drought in the root zone iscaused primarily by a poorly performing waterbalance, are more common than meteorological

droughts. Furthermore, political droughts, wherefailures in the agricultural sector are blamed ondrought, are commonplace.

Given the previous message the questionarises, why is everybody blaming drought whenthere are famines and food shortages? Theanswer is that even if there is no drought interms of rainfall, the crop may suffer fromdrought in the root zone, in terms of lack ofgreen water or soil moisture. Often land degra-

dation and poor management of soil fertility andcrops are the major and more frequent causes ofdroughts. These are referred to as agriculturaldroughts where rainfall partitioning in thefarmers fields causes water stress. Availablewater as rainfall is not utilized fully for plantgrowth. The main cause is therefore manage-ment rather than meteorologically significantrainfall deficits.

Evidence from water balance analyses on

farmers fields around the world shows thatonly a small fraction, generally less than 30% ofrainfall, is used as productive green water flow(plant transpiration) supporting plant growth(Rockstrm, 2003). Moreover, evidence fromsub-Saharan Africa shows that this range variesfrom 15 to 30% of rainfall, even in the regionsgenerally perceived as water scarce (Fig.1.10). This range is even lower on severelydegraded land or land where yields are lower

than 1 t/ha. Here, as little as 5% of rainfall maybe used productively to produce food. In aridareas typically as little as 10% of the rainfall isconsumed as productive green water flow (tran-spiration) with 90% flowing as non-productiveevaporation flow, i.e. no or very limited bluewater generation (Oweis and Hachum, 2001).For temperate arid regions, such as WANA, alarger portion of the rainfall is generally con-sumed in the farmers fields as productive green

water flow (4555%) as a result of higher yieldlevels (34 t/ha as compared with 12 t/ha).Still, 2535% of the rainfall flows as non-productive green water flow, with only some1520% generating blue water flow.

This indicates a large window of oppor-tunity. Low current agricultural yields in rainfedagriculture, which are often blamed on rainfalldeficits, are in fact often caused by other factors

than rainfall. Still, what is possible to produceon-farm will not always be produced, especiallynot by resource-poor, small-scale farmers. Thefarmers reality is influenced by other con-straints such as labour shortage, insecure landownership, capital constraints and limitation inhuman capacities. All these factors influencehow farming is done, in terms of timing of oper-ations, effectiveness of farm operations (e.g.

weeding and pest management), investments infertilizers and pesticides, use of improved cropvarieties, water management, etc. The finalproduce in the farmers field is thus stronglyaffected by social, economic and institutionalconditions.

High risk and increase with climate change

Rainfed agriculture is a risky business due tohigh spatial and temporal variability of rainfall.Rainfall is concentrated in short rainy seasons(approximately 35 months), with few intensiverainfall events, which are unreliable in temporaldistribution, manifested by high deviations fromthe mean rainfall (coefficients of variation ofrainfall as high as 40% in semi-arid regions)(Wani et al., 2004). In fact, even if water is

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