Improving Water Use Efficiency for Sustainable Agriculture

Abstract

Fresh water resources are becoming scarce and polluted while their demands for agriculture, domestic, industrial, environmental and recreational uses are on a continuous rise around the globe. Traditional ways to increase yield by extending the area under cultivation, using high intensity of external inputs and breeding for yield potential in high input agro-ecosystems offer limited possibilities under limiting resource availability. Improved agricultural systems should ensure high yields via an efficient and sustainable use of natural resources such as water. This prospect has evoked calls for a “blue revolution” based on the core idea of obtaining more crop per drop of water. This chapter presents approaches to improve water use efficiency by better crop, soil and irrigation management, and analyses underlying physiological and hydrological mechanisms. We found that most man- agement measures contribute to better water use efficiency by improving water availability to the crop while reducing unproductive water losses. The main effect of crop, soil and irrigation management is an increase of the transpiration component in relation to runoff, soil evaporation and drainage. Also the effect of deficit irriga- tion methods is achieved partially by reducing stomatal conductance that results in higher transpiration efficiency. Redistribution of water from soil evaporation to plant transpiration is the key for better water use efficiency of residue management and most measures in crop rotation design. Improved water use efficiency by better agronomy is achieved most effectively by an integral set of measures that are evalu- ated over the whole crop rotation. Processes underlying most improvements of water use efficiency in agronomy suggest that research should target plant water uptake capacity. We conclude that an integral system approach and an interdisci- plinary focus on possibilities for root system management are most promising for a better water use and sustainable productivity in agriculture