Agronomic Responses of Corn Hybrids from Different Eras to Deficit and Adequate Levels of Water and Nitrogen

Maintaining current high yields of corn (Zea mays L.) grown in the USA poses an environmental threat due to continued overuse of water and N inputs. To reduce overreliance on inputs, future corn breeding efforts should focus on improving tolerance of corn to water and N stresses, utilizing appropriate tolerance mechanisms. The objective of this study was to identify appropriate mechanisms by characterizing agronomic responses of 12 hybrids from three different eras (‘B73 x Mo17’ from 1970s and three early 1990s and eight late 1990s Pioneer brand hybrids) to varying water and N supply. This was done by growing the hybrids under deficit and adequate levels of water (one-half and full evapotranspiration) and N (0 and 200 kg ha-1) in a field study and measuring yield and other agronomic variables. While hybrid eras didn’t differ in response to varying water or N, individual hybrids varied in ability to maintain yield under water or N stress. For example, under deficit water, ‘3417’ produced 27% more yield than ‘3162’ while they yielded similarly under adequate water. Likewise, under deficit N, ‘34R07’ produced 42% more grain yield than ’33G27’ while they yielded similarly under adequate N. Agronomic variables such as kernel number per unit area were highly correlated with grain yield (r=0.98), indicating hybrid ability to maximize kernel number under varying water and N supply was critical to maximizing yield. Determining physiological mechanisms associated with to maintain kernel number under stress should be a high priority of breeding programs