drought-prone areas, where water is scarce. It does not ac­cumulate salt in the root zone and causes little soil erosion. Drip systems use 30 to 60% less water than furrow or sprin­kler irrigation (Postel, 1996). In India, crop yields from drip irrigation were about 10 to 30% higher than those from surface irrigation (Postel, 1999). Despite the efficiency in water use, drip irrigation still is used on very little of the total irrigated area. In Australia, the percentage was about 7.8%. In China and India, it was below 0.1%. The large initial investment required for the equipment is a main con­straint to its use in developing countries. Drip irrigation is used primarily to irrigate high-value horticultural crops.
     Supplemental irrigation is the application of water at critical times. It can substantially improve yield and water productivity in arid and semiarid environments. In dry ar­eas, supplemental irrigation can boost productivity of irri­gation water by 10 to 20% (Oweis and Hachum, 2003). Technology for supplemental irrigation ranges from farm ponds to shallow groundwater pumped with treadle pumps (Barker and Molle, 2004). Supplemental irrigation could

prevent total crop failure and stabilize and improve crop yields. However, it requires comprehensive knowledge and skills in crop management. Weather forecasts reduce risk and are an integral part of such a comprehensive strategy.

2.2.1.2   Water management in rainfed crop farming systems
Compared with irrigated agriculture, rainfed systems have been given little attention in most ESAP countries. The pau­city of technology for rainfed areas partly relates to deci­sions by government authorities to concentrate research and extension in irrigated areas because they have been per­ceived more likely to yield a greater return on investment. Among the many constraints that limit rainfed agriculture, unreliable rainfall is probably the biggest. Water stress at the flowering stage of maize can reduce yield 60%, even if water is adequate during the rest of the season (Molden and de Fraiture, 2004). Recent years have seen increased biological science efforts to produce traits for drought toler­ance and resistance to many pests and diseases.