Response of maize hybrids under limited irrigation capacities: Crop water use

Maize (Zea mays L.) production in the semiarid Texas High Plains (THP) often suffers exceptional yield reductions when irrigation cannot meet seasonal and peak water requirements. Drought-tolerant hybrids may reduce yield losses resulting from water stress by altering seasonal soil water use patterns to permit greater uptake during yield-sensitive growth stages. We examined the effect of irrigation capacity (8.47 and 4.23 mm d(-1)) and planting rates (74,000 and 95,000 seeds ha(-1)) during three growing seasons (2016-2018) on water use of three maize hybrids, two of which were considered drought tolerant. Changes in stored soil water were examined for the entire profile and for segregated depth increments (0-0.4, 0.4-0.8, and 0.8-1.4 m). Seasonal crop evapotranspiration averaged 754 and 592 mm across years for the high and low irrigation capacities, respectively. Irrigation level significantly affected seasonal change in stored soil water in 1 yr (2018) with greater depletion at harvest under the low irrigation capacity. Soil water use at 0.8-1.4 m comprised <4% of seasonal water use. Hybrids did not differ with respect to growing season crop water use. Stored soil water throughout the growing season within the examined depth increments were similar among hybrids and plant densities, with significant differences occurring infrequently and being inconsistent across years. Drought-tolerant traits may have a diminished effect on transpiration in this study because of the dense soil-limiting root proliferation or the high atmospheric demand at the study location.