Supplemental irrigation (SI) or Deficit irrigation (DI) of rainfed cropsGlobal


Supplemental irrigation (SI) or Deficit irrigation (DI) has been extensively investigated as a valuable and sustainable production strategy for a wide range of crops in dry regions. By limiting water applications to drought-sensitive growth stages, this practice aims to maximize water productivity and to stabilize – rather than maximize – yields (Geerts and Raes 2009 1, FAO 2002 2). It involves the addition of limited amounts of irrigation water to essentially rainfed crops, in order to improve and stabilize yields during times when rainfall fails to provide sufficient moisture for normal plant growth. Unlike full irrigation, the timing and amount of SI cannot be determined in advance given the natural variability in season-to-season and within season rainfall levels (Oweis and Hachum 2012). 3

Relationship to CSA

As well as achieving higher water productivity, the productivity and stability of crop production can be greatly increased through the addition of small amounts of SI at the correct time. For example, in Northern Iraq, where huge investments have been made in SI, rainfed wheat yields in 1997/98 increased from 2.2 to 4.6 t/ha with only the addition of 63 mm of SI in a season of 236 mm rainfall (Oweis and Hachum 2012). 3 SI has substantial adaptation benefits through the reduction and elimination of the short-term risk of yield losses or crop failure in rainfed crops due to water stress at critical stages, an adaptation benefit which is likely to become even more important in the future in regions where rainfed agriculture is important and where climate change projections suggest lower and more variable rainfall amounts.

Impacts and lessons learned

Given the unpredictable nature of SI scheduling, the best water delivery systems are those which can be used ‘on demand’, for instance, where farmers have access to wells or nearby water sources. In addition, in most instances, farmers will need an effective extension system which is able to advise them on the timings and amounts of SI scheduling. In many communities, the available water supply is inadequate to irrigate all of the available land. In those cases, farmers might consider the communal benefits of allowing sub-optimal yields on their individual fields, by practicing SI, so that the water saved might be used to irrigate additional land in the community (Geerts and Raes 2009 3, Oweis and Hachum 2012 3).


  • 1

    Geerts S, Raes, D. 2009. Deficit irrigation as an on-farm strategy to maximize crop water productivity in dry areas. Agricultural Water Management 96(9):1275–1284. Deficit irrigation (DI) has been widely investigated as a valuable and sustainable production strategy in dry regions. By limiting water applications to drought-sensitive growth stages, this practice aims to maximize water productivity and to stabilize – rather than maximize – yields. We review selected research from around the world and we summarize the advantages and disadvantages of deficit irrigation. Research results confirm that DI is successful in increasing water productivity for various crops without causing severe yield reductions. Nevertheless, a certain minimum amount of seasonal moisture must be guaranteed. DI requires precise knowledge of crop response to drought stress, as drought tolerance varies considerably by genotype and phenological stage. In developing and optimizing DI strategies, field research should therefore be combined with crop water productivity modeling.
  • 2

    FAO. 2002. Deficit Irrigation practices. Water Reports 22. Rome, Italy: Food and Agriculture Organization of the United Nations. This publication presents the results of a number of deficit irrigation studies carried out for various crops and under various ecological conditions, with a review of the impact of reduced water supplies on crop yield. The results of the studies are presented in ten contributions prepared by a team of scientists specialized in deficit irrigation. The articles were prepared at the request of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture in close collaboration with the FAO Land and Water Development Division.
  • 3

    Oweis T, Hachum A. 2012. Supplemental irrigation: a highly efficient water-use practice. Aleppo, Syria: ICARDA. This book emphasizes the need greater for a better balance of investments in rainfed versus irrigated agriculture. We need a new governance, investment and management paradigm in which all water options in the farming system are considered. The book highlights several other aspects including water productivity, integration, and participatory research and development. In rainfed dry areas, where water (not land) is the most limiting factor, the priority should be to maximize yield per unit of water, rather than yield per unit of land. Supplemental irrigation can play a key role in increasing water productivity, and in ensuring more sustainable use of groundwater. For maximum benefit, supplemental irrigation must be part of an integrated package that includes non-water inputs, improved crop management methods and other components. Optimal supplemental irrigation regimes would be based on sound water management policies, economic evaluations (e.g. crop:water price ratios) and timely application. As past experience has shown, integrated, farmer-participatory research and development programs are the best way to introduce, test and scale out supplemental irrigation technology.

Welcometoclimate-smart agriculture 101

scroll to discover

This site is your gateway to implementing climate-smart agricultureIt will help you get started and guide you right through to implementation on the ground, connecting you with all the resources you need to dig deeper.

scroll to start

CCAFS Climate-Smart Agriculture 101

The basics

Climate-smart agriculture (CSA) is an integrative approach to address these interlinked challenges of food security and climate change, that explicitly aims for three objectives:

A. Sustainably increasing agricultural productivity, to support equitable increases in farm incomes, food security and development;

B. Adapting and building resilience of agricultural and food security systems to climate change at multiple levels; and

C. Reducing greenhouse gas emissions from agriculture (including crops, livestock and fisheries).

Entry points

Agriculture affects and is affected by climate change in a wide range of ways and there are numerous entry points for initiating CSA programmes or enhancing existing activities. Productivity, mitigation and adaptation actions can take place at different technological, organizational, institutional and political levels. To help you navigate these myriad entry points we have grouped them under three Thematic Areas: (i) CSA practices, (ii) CSA systems approaches, and (iii) Enabling environments for CSA. Each entry point is then described and analysed in terms of productivity, adoption and mitigation potential and is illustrated with cases studies, references and internet links for further information.

Develop a CSA plan

Planning for, implementing and monitoring CSA projects and programmes evolves around issues of understanding the context including identification of major problems/barriers and opportunities related to the focus of the programme; developing and prioritizing solutions and designing plans; implementation; and monitoring and evaluation. Most major development agencies have their own framework for project and programme formulation and management but CCAFS has developed a specific approach for planning, implementing and assessing CSA projects and programme called CSA plan. CSA plan was developed to provide a guide for operationalizing CSA planning, implementation and monitoring at scale. CSA plan consist of four major components: (1) Situation analysis; (2) Targeting and prioritizing; (3) Program support; and (4) Monitoring. evaluation and learning.


To meet the objectives of CSA, such as agricultural development, food security and climate change adaptation and mitigation, a number of potential funding sources are available. For instance, climate finance sources may be used to leverage agriculture finance and mainstream climate change into agricultural investments. This section offers an overview of potential sources of funding for activities in climate-smart agriculture (CSA) at national, regional and international levels and for a number of different potential ‘clients’ including governments, civil society, development organizations and others. Additionally, it includes options to search among a range of funding opportunities according to CSA focus area, sector and financing instrument.

Resource library

CSA Guide provides a short and concise introduction and overview of the multifaceted aspects of climate-smart agriculture. At the same time it offers links to references and key resources that allows for further investigations and understanding of specific topics of interest. In the resource library we have gathered all the references, key resources, terms and questions in one place for a quick overview and easy access that can be used as a part of or independently of the other sections of the website. The resource library is divided into six sections; (1) References – list all publications, links and blogs referred to on the website; (2) Tools – list all the CSA tools presented on the website; (3) Key terms – explains the most important and frequently used terms related to CSA; (4) Frequently asked questions (FAQ) – provides a rapid overview of the most common questions asked on climate-smart agriculture; (5) About – where you can find out more about the purpose and structure of, as well as on the organizations and authors behind the website; (6) Contact.

Case studies

Local case studies

Filter by entry points