Evapotranspiration

This document discusses evapotranspiration (ET), which is the combination of evaporation from soil and transpiration from crops. ET depends on factors like solar radiation, temperature, humidity, wind speed, soil water availability, and crop development. Early in the growing season when crops are small, most water loss is from soil evaporation, but as crops develop and their canopies shade more of the ground, transpiration becomes the dominant process of ET. The rate of ET is typically expressed in millimeters of water lost per time period, like 1 mm per day.