Water use by crops as affected by climate and plant factors

The weather largely determines the use of water, or evapotranspiration (ET), by most crops during times when the plants are healthy and fully shade the ground. Even under full-cover conditions, however, the evapotranspiration of various crops can vary significantly with differences in stomatal or surface resistance, reflectance, and aerodynamic roughness. However, during early stages of crop growth, transpiration is very limited, and the controlling factor in water use is basically the moisture status of the soil surface. How frequently the surface receives water from rain or irrigation—along with the weather conditions—largely determines evapotranspiration rates.