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The great challenge of the agricultural sector in countries located in arid and semiarid regions faced with severe water scarcity is to produce more food from less water. This may be achieved by increasing the crop water productivity (WP). Based on experiments conducted in different regions of Iran, it was found that the range of wheat WP was greater than that reported earlier by the FAO. The maize WP was high in the northwestern regions of Iran and less in the southwest. The wide ranges of WP (0.5-1.8 kg m À3 for wheat and 0.3-2.3 kg m À3 for maize) indicate tremendous opportunities for increasing agricultural production with less water. The variability of crop WP can be ascribed to climate, cropping calendar, soil characteristics, and irrigation water management. Wheat and maize WP of 1.5 and 1.7 kg m À3 were recommended as an optimum level to be considered in the cropping system of potential regions. Irrigation water applied for an optimum level of wheat and maize WP was about 2650 and 5900 m 3 ha À1 , respectively. The maximum wheat WP occurred under deficit irrigation, while for maize it was measured under full irrigation. Regions with higher annual rainfall and high silt content in soil were more productive under deficit irrigation management. Copyright # 2008 John Wiley & Sons, Ltd.key words: crop water productivity; crop water production function; wheat; maize; deficit irrigation

Water is the most limiting factor for crop production in arid and semiarid areas. The search of promising water management strategies is foremost for achieving highly productive and sustainable agriculture. Irrigation water management, water conservation, and nonconventional water use for agriculture are key issues to be considered by the National Agricultural Research Systems (NARS) in these areas. According to climate change scenarios and population growth predictions, these countries will undergo even severe water scarcity levels. Failure of resolving food production challenge will exacerbate tensions between countries, wars, and illegal immigration and compromise human, social, economic, and sustainable development in these areas. However, the search for innovative solutions to water scarcity must comply with societal values, environmental sustainability, and market growth.

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A mangrove ecosystem restoration project was carried for 3 years in the Mauritanian side of the River Senegal Delta where scarce scientific and/or technical references exist on these mangroves located in the northernmost limit on the West African coast. The construction of the Manantali and the Diama dams transformed the once exhuberant delta to an artificial estuary and had dramatically affected the inland mangrove ecosystems. Thousands of mangrove seedlings were grown annually in the PND and community nurseries. A participatory approach was adopted for mangrove plantings where chicken and goat manure was used as biological fertilizer. Finally, 42.000 mangrove trees were planted in 4 sites located in the area of the Park. Two years after planting, the mangrove trees reached a height of about 2 m, and constitute already a source of forage for herds of camels and goats. Success of such project in a fragile and desert environment could set the way for future mangrove restoration projects in Mauritania or other less hostile areas.