Agronomic Responses of Corn Hybrids to Drought Stress and Nitrogen Supply.

Drought-tolerant corn (Zea mays L.) hybrids can reduce yield losses associated with dry growing conditions. An experiment was conducted in 2013 on a Hubbard-Mosford loamy sand complex in three fields in Minnesota to compare the agronomic performance of a drought-tolerant hybrid and a non-drought-tolerant (‘standard’) hybrid under managed drought stress. Soil water content and calculated evapotranspiration, coupled with drip irrigation were used to create: i) no drought stress; ii) sustained drought stress from the 14-leaf-collar stage (V14) until physiological maturity (R6); and iii) sustained drought stress from the blister stage (R2) until R6. Sub-optimal, optimal, and supra-optimal fertilizer N rates were applied to each combination of hybrid and drought stress. Averaged across hybrids, grain yield was 14.8 Mg ha^-1 in the absence of drought stress with the supra-optimal N rate. Grain yield was 10% greater with the drought-tolerant hybrid than the standard hybrid when drought stress occurred from V14 to R6, but did not differ between hybrids in the absence of drought stress or when drought stress began at R2. Averaged across all levels of drought stress, silage yield of the drought-tolerant hybrid was 5 and 10% greater than that of the standard hybrid at the optimal and supra-optimal N rates, respectively. Kernel mass and number did not differ between hybrids in the absence of drought stress, but with drought stress the drought-tolerant hybrid produced more, but lighter, kernels than the standard hybrid. Total crop N uptake was reduced with drought stress and with the sub-optimal N rate. The drought-tolerant hybrid had 9% greater total crop N uptake than the standard hybrid at the supra-optimal N rate, but there was no difference between hybrids at lower N rates. Greater grain yield of the drought-tolerant hybrid in water-limited conditions was related to greater aboveground biomass, N uptake, and kernel number.