In order to obtain high crop yields, corn requires between 20 to 25 inches of water per growing season. A low yield can be obtained from 15 to 16 inches of water, but will depend on what part of the season the water is available. It takes 27,000 gallons to equal 1 inch of water per acre.
Between 70 to 80 percent of crop water is used by plant transpiration, with the balance being lost by evaporation from the soil surface. The degree of water used daily by corn will be affected by atmospheric conditions. Low humidity, high air temperatures, clear skies and high wind speeds will result in greater daily water demands. Irrigation water can be used to supplement rainfall and the water contained in the soil profile.