RESPONSE OF DROUGHT-TOLERANT CORN TO VARYING IRRIGATION LEVELS IN THE TEXAS HIGH PLAINS

Corn (Zea mays L.) for grain continues to be an important crop for livestock feed in the Texas High Plains (THP) region despite lackluster prices. It offers greater crop water productivity compared with other crops grown in the region but also has a relatively high water requirement, which must be met by irrigation. The sole water resource in the region is the Ogallala Aquifer, which is declining because withdrawals exceed recharge, and this is of major concern. Producers are interested in the performance of drought-tolerant (DT) corn, but data on DT crop production functions are limited. From 2015 to 2017, studies of DT corn response to different irrigation treatments were conducted in the THP at Bushland, Texas. Results showed that grain yields, seasonal evapotranspiration (ETc), and crop water use efficiency (WUE) varied significantly between seasons and among different DT hybrids. Comparisons between a mid-season (MS) and an early-maturing (EM) hybrid showed: (1) at the severe deficit irrigation treatment level, grain yields were low, but the EM hybrid produced 400% more grain; (2) at the moderate deficit irrigation treatment level, grain yields and ETc were similar; and (3) at the full irrigation treatment level, the EM hybrid required 75 mm less water, but it produced 24% less grain. Non-hail damaged MS DT corn produced grain yields that were numerically greater than conventional corn grown in the THP in an optimal year. However, during drought seasons, DT hybrid response was not improved over conventional hybrids under severe deficit irrigation. This study demonstrated that MS DT corn hybrid P1151AM, irrigated at a level that fully met evapotranspiration demand, resulted in grain yield and WUE levels that were near the upper limits for corn produced in the THP. Further research is needed to determine the constancy of response among different DT hybrids under favorable and drought conditions.