Impacts of drought intensity and weed competition on drought-tolerant corn performance

Water stress and weed competition are critical stressors during corn (Zea mays L.) development. Genetic improvements in corn have resulted in hybrids with greater tolerance to abiotic and biotic stressors; however, drought stress remains problematic. Therefore, in light of the anticipated change in precipitation throughout the Great Lakes Region, greenhouse experiments were conducted to evaluate water stress and weed competition on drought-tolerant corn performance. The study followed a completely randomized block design with four replications. Factorial treatment combinations consisted of drought-tolerant corn competition (presence or absence), water stress (100% or 50% volumetric water content [VWC]), and nine corn:common lambsquarters (Chenopodium album L., CHEAL) densities. Corn and C. album growth parameters were measured at 14 and 21 d after water-stress initiation. To explore the impact of reduced soil moisture and weed competition on corn and C. album growth parameters, photosynthetic response, and biomass, linear mixed-effects and nonlinear regression models were constructed in R. Chenopodium album biomass was reduced by 46% and 50% under corn competition at 2 and 4 weeds pot(-1) (P = 0.0003, 0.0004). However, introducing crop competition under 6 and 9 weeds pot(-1) did not reduce C. album biomass (P = 0.90, 1.00). Averaged across weed pressures, corn biomass was 22% less when grown under 50% compared with 100% VWC (P = 0.0003). However, averaged across VWC values, increasing weed competition from 0 to 2 (P = 0.04), 4 (P = <0.0001), 6 (P = 0.0002), or 9 (P = 0.0002) weeds pot(-1) reduced biomass by 22%, 38%, 35%, and 36%. Overall, water stress and C. album competition negatively affected the parameters measured in this study; however, the magnitude of reduction is stronger under drought stress than increasing weed competition when water is not limiting. Therefore, field crop growers must modify current integrated weed management programs to maintain yield under future climate stress.