Water requirement depends both on the previously mentioned atmospheric conditions and crop variety. Longer-season corn varieties use more water, but they also produce more grain if the heat units and water supply are available. If both varieties are able to mature fully, the grain produced for each inch of ET is approximately equal. The difference in seasonal water use is due to total days of water use, not a difference in daily water use. I shows average crop water use figures by growth stage for a generic, 120-day maturity variety planted in south central Nebraska.
Corn is more sensitive to water stress than other field crops.
For optimum yields, adequate soil water is essential. A full moisture profile in the potential root zone at the beginning of the growing season is desirable for optimal crop performance. In central and eastern Nebraska off-season precipitation is usually sufficient to fill the soil profile. Additionally, topsoil water must be available for the critical germination and emergence periods. Corn does not extract water uniformly throughout its rooting depth.