ABSTRACT
In view of the increasing demand for water for nonagricultural uses (such as for urban and industrial uses), and also to rationally redeploy available water resources for more areas of crop production, it is important to optimize the use of water for crop production [1]. Agricultural research has a major responsibility to develop and use techniques and practices that will result in more effective use of water in farming systems. This involves improvement of water use efficiency (WUE), defined here as aerial dry matter production of a crop per unit of evapotranspiration (ET). Transpiration efficiency (TE) is a component of WUE, being aerial dry matter production per unit of water transpired by the crop. The difference between WUE and TE is important, as suppression of soil evaporation and transpiration by weeds can improve WUE without improving TE, which is a direct measure of the crop species performance. Plant attributes (canopy structure, rate of canopy development, etc.) and management means (manipulating plant population, optimizing planting dates, fertilizer management, etc.) can modify soil evaporative losses (Es) relative to transpiration (T) and can therefore affect WUE to a greater extent than TE.
