SHORT-TERM AND LONG-TERM RESPONSES OF CORN TO A PREANTHESIS SOIL-WATER DEFICIT

Irrigation should be scheduled in order to minimize water application while maximizing crop yield, and such judicious watering requires better understanding of how crops respond to water supply. This field study was initiated to determine the influence of water deficits prior to anthesis on growth and yield of corn (Zea mays L.) grown in a sandy soil. A rain shelter was employed to provide periods without water of 21 d in 1988 and 18 d in 1989. Water deficit treatments were begun as the eighth or ninth leaf emerged from the whorl of plants for two corn hybrids. Control plots were irrigated to maintain plant available water (PAW) at 80% or greater throughout the growing season. A correlation between leaf extension and PAW revealed relative growth of deficit plants declined linearly beginning at 85% PAW, and approached zero at 25% PAW. Short-term effects of the water deficits were delayed leaf tip emergence and decreased production of leaf area. Long-term consequences were manifested in the form of reduced final sizes of certain leaves and internodes; delays of tassel emergence, silk emergence, the onset of grain filling by 2 to 3 d; and yield losses of 15 to 25%. Decreased yield of deficit plants was attributed to a reduction in the number of well-developed kernels.