Water use efficiency in crop production at different spatial and temporal scales

Water is essential for plant life but it is also the most limiting factor for their growth. The temporal variation in the supply of soil water from precipitation, the spatial variability of soil factors and landscape irregularities influencing soil water supply for crop plants affect food production and create a risky environment for growing crops. Increases in crop production per unit of water used is imperative for supplying adequate food, feed and fiber in an environment where future water supplies are not expected to increase substantially. Field studies indicate that when yield from crops with common development patterns are increased by better crop management, water use efficiency (WUE) is also increased. Increased yields from genetic improvement usually result in an increased WUE with the possible exception where season length is different. The objective of this review is to present the state of the art of research in the field of WUE and future perspective to optimize water resources in agriculture. Significant results will be presented considering the important issue of spatial and temporal scale.