Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 6, 2000
Publication Date: N/A
Interpretive Summary: Water is a critical need for crop production and is often the most limiting factor to profitable yields. Even in areas with higher rainfall, lack of sufficient soil water supplies at critical growth stages causes a reduction in yield. Water use efficiency is expressed as the crop dry matter or yield production per unit of water used by the plant. Water use efficiency can be changed by increasing the amount of water used by the plant or increasing the growth and yield of the plant. Soil management practices, e.g., tillage and residue management, and plant nutrient practices, e.g., the addition of nitrogen and phosphorus, have a positive impact on water use efficiency. Crop producers in more water-limited areas have used water use efficiency as a method of comparing farming systems. In the higher rainfall areas, water use efficiency can be used to improve nutrient management practices across fields. A survey of the literature from around the world has shown that potential exists to increase crop yield per unit of water used. Producers have begun to use this approach to evaluate farming practices, which could lead to improved nutrient use efficiency and more stable yield across years with variable weather.
Water use efficiency represents a given level of biomass or grain yield per unit of water used by the crop. The relationship between water use and biomass or grain yield has been found to be generally linear. With increasing concern about the availability of water resources in both irrigated and rainfed agriculture, there is renewed interest in trying to develop an understanding of how water use efficiency can be improved and farming systems modified to be more efficient in water use. Soil management practices affect the processes of evapotranspiration by modifying the energy available, the water available in the soil profile, or the exchange rate between the soil and the atmosphere. Plant management practices, e.g., the addition of nitrogen and phosphorus, have an indirect effect on water use through the physiological efficiency of the plant. A survey of literature reveals a large variation in measured water use efficiency across a range of climates, crops, and soil management practices. It is possible to increase water use efficiency by 25-40% through soil management practices that involve tillage. Overall, precipitation use efficiency can be enhanced through adoption of more intensive cropping systems in semiarid environments and increased plant populations in more temperate and humid environments. Modifying nitrogen and phosphorus fertilizer practices can increase water use efficiency by 15-25%. We can increase water use efficiency, and experiences at field scale experiments show these changes can have a positive effect on crop yield.