ABSTRACT
Water is the essence of life, and it plays vital roles in the biology of plants. In addition to its roles within the plant, evaporation of water from stomatal apertures provides for carbon dioxide entry into the leaf with carbon being fixed into organic matter through photosynthesis. Plants use a considerable amount of water to gain the required carbon, and ‘‘water use efficiency’’ (WUE) is the term used to quantify the yield, obtained through fixing of carbon, for the water lost. There are various ways, at the plant and farm level, to increase WUE as exemplified by the use of deficit irrigation (DI). The DI involves supplying less water to plant stands than the prevailing evapotranspiration (ET), a term combining transpiration (T) from plants and evaporation (E) from the soil. When yield is plotted against applied irrigation water, the relationship is called crop water production function (CWPF). Each point on CWPF could, therefore, relate to WUE. The availability of CWPF for each major crop in each region will facilitate the proper management of water resources. Many publications on various crops relate yield to water use and especially yield and applied irrigation water. A comprehensive coverage for various economically important herbaceous plants was given by Doorenbos and Kassam.[1] The following short treatment focuses on some basic definitions relating the yield to water use of crop plants.
