Supplemental Irrigation: A Highly Efficient Water‐Use Practice - 2nd Edition

Rain-fed agriculture accounts for about 80% of the world’s farmland and two-thirds of global food production. Despite the higher risks and generally lower productivity compared to irrigated areas, rainfed agriculture will continue to play a dominant role in providing food and livelihoods for an increasing world population. Yields of rainfed crops, particularly in developing countries, are low as a result of moisture deficits, inappropriate management of soil, water and nutrients, and lack of other production inputs. But rainfed systems have huge untapped potential, especially in Asia and Africa, where the bulk of the world’s poor live. This potential can be realized through improved technologies, sound water policy and greater investment. This book describes one technology – supplemental irrigation (SI) – that has been extensively tested, widely adopted, and has generated substantial impacts in different countries. In many rainfed environments, shortage of soil moisture often occurs during the most sensitive stages of crop growth, i.e. flowering and grain filling. This can severely affect plant growth and yield. Supplemental irrigation – the application of limited amounts of water during critical crop growth stages – can substantially increase yield and water productivity. In 1997, ICARDA published Supplemental irrigation: a highly efficient water-use practice, an illustrated booklet describing the principles and practical application of SI. With continuing demand for copies, it was reprinted numerous times, and translated into Arabic, Russian, French, Persian and Pashto. During the 15 years since its publication, there have been significant advances in SI experiences. We have therefore extensively revised the booklet, to include recent developments on experimental research stations as well as farmers’ fields. The new edition 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. SI can play a key role in increasing water productivity, and in ensuring more sustainable use of groundwater. For maximum benefit, SI must be part of an integrated package that includes non-water inputs, improved crop management methods and other components. Optimal SI 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 SI technology. The information presented here is drawn largely from research projects, training programs, technical workshops and other initiatives by ICARDA and its partners. We hope this revised edition will be even more useful than the 1st edition, in learning from past experience and building on previous work to strengthen smallholder agriculture under ever more challenging conditions.