Midseason Soil Water Recharge for Corn in the Northwestern Corn Belt

Abstract

Incomplete soil water recharge between growing seasons and insufficient growing-season precipitation limit plant growth in southwestern Minnesota. Field experiments were conducted from 1979-81 on a Nicollet clay loam soil (Aquic Hapludoll) to determine the effects of midseason soil water recharge on corn (Zea mays L.) production. Six treatments consisting of timing and amount variables of supplemental water addition were studied. "Daily precipitation and air- temperatures were measured. Soil water contents and potentials were measured with a neutron probe and tensiometers, respectively. Progressive developmnent of soil water deficiencies occurred during the three-year study. Following a wet year in 1979, a shallow-receding water table was present during the 1980 growing season. Extensive soil water depletion to 90 cm occurred in both 1980 and 81, the water table could not be detected within 200 cm of the soil surface in 1981. Despite these diverse conditions, positive and significant grain yield responses to the addition of supplemental water were observed in each year of the study. Grain yield resulting from the midseason application of 7.6 cm of water exceeded grain yield with natural precipitation by 1808, 2130, and IB47 kg/ha tn 1979, 80, and 81, respectively. Grain production was enhanced as effectively by single-midseason applications of 7.6 cm of water as by "optimum irrigation" (application of 3.8 cm at 50 percent depletion of plant-available water to a soil depth of 90 cm). In the presence of a receding water table (1980), 90 percent of the grain yield variability and 92 percent of the variability in total dry matter-production (TMDP) was accounted for by the amount of supplemental water added and early-season water table depth. Response to the addition of supplemental water diminished with decreasing early-season water table depth.