certain location (through participatory decentralized cropbreeding programs) may use water more productively if managed adequately than varieties or landraces with inferior yield potential.

The choice of optimal planting date can, in combination with short-duration varieties within suitable crop rotations, increase water productivity substantially by making the best possible use of limited precipitation and by moving the cropping season into a period of low evaporative demand (“seasonal shifting”; see van Duivenbooden et al., 2000). Improved meteorological forecasting and supplemental irrigation, possibly combined with mechanization, may greatly facilitate moving the cropping season for better water-use efficiency.

Appropriate crop rotations or relay and intercropping practices, including food legumes that fix atmospheric nitrogen, also make better use of limited precipitation; growing a legume crop instead of fallowing every second year has proved to increase water productivity substantially in cereal production in West Asia and North Africa (WANA) (van Duivenbooden et al., 2000). In addition, crop rotations may reduce weed, pest and disease pressure and positively influence soil fertility and structure.

Mulches of crop residues combined with appropriate soil management may not only reduce unproductive evaporative water loss from the soil surface but also enhance infiltration of scarce precipitation. Mulches may thus reduce wind erosion, soil temperature and surface sealing, and contribute to improved water productivity if their effect on soil temperature does not prolong the crop growing period into a dry season. A large soil volume that crop roots can explore is crucial for storing water for crops to use. Therefore, management factors that increase soil depth and give roots access to soil volume are important for making optimal use of scarce water. Such factors include breaking impermeable layers, building terraces and other structures to mitigate erosion, fertilizing for vigorous root growth and increasing soil water-holding capacity. Particularly in windy areas windbreaks may reduce evapotranspiration through an ameliorated microclimate and thus improve water-use efficiency provided that competition of the windbreak species (usually trees) does not limit crop production. Other options such as dense canopies, ground cover, shade, plastic tunnels and greenhouses can reduce evapotranspiration and increase the relative humidity of the ambient atmosphere, greatly increasing water-use efficiency.

In many cases, such as mulching or adequate soil management, some degree of mechanization may greatly support management practices fostering a more efficient use of limited water resources and precipitation. Furthermore, profitable markets and access to them are a general prerequisite that strategies and practices for increasing crop and water productivity can be implemented (profitability of investments required). Often access to credit at a reasonable interest rate is required to ensure that necessary investments can be profitably made. Rainfed cropping. In addition to the above-listed general strategies and practices to increase crop and water productivity, certain management aspects are of particular importance in rainfed cropping. To store as much water as

possible in the soil, maximizing infiltration of precipitation and reducing runoff is a major priority for improving the water supply to crops in environments where water is a limiting factor for plant growth.

Water-harvesting technologies of collecting, storing and concentrating precipitation at micro, meso and macro scale may not only increase crop productivity in dry areas but make it possible to produce crops in environments where cropping would not be possible without such technologies, because they minimize the risk of crop failure. Additionally, water harvesting may protect land from degradation and desertification. Developing and using drought-tolerant or drought-resistant plant material with high yield potential is a prerequisite in the drought-prone areas of CWANA if irrigation is not available or feasible. Recent evidence shows that prospects for improving yields and water productivity in rainfed agriculture are considerably more promising than previously assumed (Rosegrant and Cai, 2000; Rosegrant et al., 2002; Comprehensive Assessment of Water Management in Agriculture, 2007 vs. Seckler and Amarasinghe, 2000). A change in breeding strategy to directly target rainfed areas rather than relying on “spill-in” from breeding for irrigated areas seems key to this development (Rosegrant et al., 2002).

However, policy changes, such as providing a policy environment that does not discriminate against rainfed areas, and infrastructure investment in these areas, such as access to input and output markets, are required to increase productivity in rainfed cropping. Decision-making power will have to be increasingly delegated to communities and social groups, particularly considering the roles of women, who actually manage the natural resources and depend on their sound management for their livelihoods. Key strategies to follow for sustainable development thus include sustaining investments in agricultural research and extension; improving coordination among farmers, NGOs and public institutions; ensuring equitable and secure access to natural resources; empowering land users for effective risk management; and increasing investment in rural infrastructure (Rosegrant et al., 2002).

Irrigated cropping. In addition to the management factors discussed above, irrigation-specific options may be considered to render irrigated cropping more water efficient and productive. Irrigation and conveyance systems should be planned and improved to minimize water loss. Piping, lining and regularly maintaining conveyance systems are ways to reduce water loss through evaporation, percolation at the bottom of canals, seepage, overtopping, bund breaks, leakage through rat holes and runoff (Brouwer et al., 1989). Optimizing water distribution in the field is key for efficient water use in irrigation (University of Arizona, 1999). Field application efficiency may be increased by improving irrigation systems and scheduling irrigation efficiently (Solomon, 1988; Allen et al., 1998). Particular attention should be paid to exploiting the potential of supplemental and deficit irrigation, which may increase water productivity tremendously (Figure 5-1) and greatly reduce the threat of crop failure (risk reduction, stability) (Oweis et al., 1999). In Syria, for example, spreading a given amount of limited irrigation water supplementing precipitation on a larger area, hereby not