WSES-4-Evapotranspiaration

Abstract

Evapotranspiration is an important component of the hydrologic cycle. Water works as the medium of absorption and transport of nutrients from the soil, plays important role in plant photosynthetic process, is medium of transport of metabolites, and forms part of structure of the plant tissues. Evapotranspiration is the basic process that governs the state and movement of water in the Soil-Plant- Atmospheric continuum (SPAC). It is itself controlled by availability of water in the root zone soil, plant characteristics including transport resistances at various stages in the SPAC, and atmospheric evaporative demand, As time after irrigation or rainfall proceeds, water from the crop root zone continously depletes, resulting in the stress condition in the root zone. Due to stress, several plant functions like photosynthesis, cell division and enlargement, nutrient uptake, and thus growth and development processes are affected resulting in to reduction in the otherwise realizable yield. Therefore it is essential to keep the root zone well supplied with water by resorting to irrigation. To qualify water status which determines the irrigation needs of a crop, it is desirable that the component of evapotranspiration is adequately quantified so that crops are irrigated at appropriate time before stress conditions may develop affecting the yield.