Evapotranspiration is both the water lost from the soil surface through evaporation and the water used by a plant during transpiration . Soil evaporation is the major loss of water from the soil during early stages of growth. As corn leaf area increases, transpiration gradually becomes the major pathway through which water moves from the soil through the plant to the atmosphere. Yield is reduced when evapotranspiration demand exceeds water supply from the soil at any time during the corn life cycle. Nutrient availability, uptake, and transport are impaired without sufficient water.
Plants weakened by stress are also more susceptible to disease and insect damage.
Corn responds to water stress by leaf rolling. Highly stressed plants will begin leaf rolling early in the day. Evapotranspiration peaks around canopy closure. Estimates of peak evapotranspiration in corn range between 0.20 and 0.39 inches per day. Water stress during vegetative development reduces stem and leaf cell expansion resulting in reduced plant height and less leaf area.