Managing soils to achieve greater water use efficiency: A review

Water use efficiency (WUE) represents a given level of biomass or grain yie ld per unit of water used by the crop. With increasing concern about the av ailability of water resources in both irrigated and rainfed agriculture, th ere is renewed interest in trying to develop an understanding of how WUE ca n be improved and how farming systems can be modified to be more efficient in water use. This review and synthesis of the literature is directed towar d understanding the role of soil management practices for WUE. Soil managem ent practices affect the processes of evapotranspiration by modifying the a vailable energy, the available water in the soil profile, or the exchange r ate between the soil and the atmosphere. Plant management practices, e.g., the addition of N and P, have an indirect effect on water use through the p hysiological efficiency of the plant. A survey of the literature reveals a large variation in measured WUE across a range of climates, crops, and soil management practices. It is possible to increase WUE by 25 to 40% through soil management practices that involve tillage. Overall, precipitation use efficiency can be enhanced through adoption of more intensive cropping syst ems in semiarid environments and increased plant populations in more temper ate and humid environments. Modifying nutrient management practices can inc rease WUE by 15 to 25%. Water use efficiency can be increased through prope r management, and field-scale experiences show that these changes positivel y affect crop yield.