Evapotranspiration (ET)
Evapotranspiration is the combined process of water evaporating from soil and transpiring from plant leaves, used to determine irrigation needs.
Evapotranspiration (ET) is the total amount of water lost from a cropped area through both soil surface evaporation and plant transpiration. It is measured in inches or millimeters per day and is the primary factor used to schedule irrigation and estimate crop water demand. Reference ET (ET₀) is calculated from weather data — temperature, humidity, wind speed, and solar radiation — using equations like the Penman-Monteith method. Crop-specific ET (ETc) is then derived by multiplying ET₀ by a crop coefficient that changes with growth stage. Matching irrigation application to ET losses prevents both water stress and wasteful over-irrigation.