Crop water use, consumptive use and evapotranspiration (ET), are terms used interchangeably to describe the water consumed by a crop. This water is mainly used for cooling purposes; a negligible amount is retained by the crop for growth. For more information on ET and growth stages, refer to fact sheet 4.715, Crop Water Use and Growth Stages.
Water requirements of crops depend mainly on environmental conditions. Plants use water for cooling purposes and the driving force of this process is prevailing weather conditions. Different crops have different water use requirements, under the same weather conditions. Crops will transpire water at the maximum rate when the soil water is at field capacity.
When soil moisture decreases crops have to exert greater forces (energy) to extract water from the soil. Usually, the transpiration rate doesn’t decrease significantly until the soil moisture falls below 50% of available water capacity.
Knowing seasonal crop water requirements is crucial for planning your crop planting mixture especially during drought years.