|Caldwell, Robert - U OF NE/LINCOLN NE|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 19, 2004
Publication Date: December 1, 2004
Citation: Oneill, P.M., Shanahan, J.F., Schepers, J.S., Caldwell, R. 2004. Agronomic responses of corn hybrids from different eras to deficit and adequate levels of water and nitrogen. Agronomy Journal 96:1660-1667. Interpretive Summary: Average corn yields have improved dramatically in the U.S. over the last 50 years, and this is mainly the result of combined use of irrigation practices, greater nitrogen fertilizer use, improved hybrids, and a host of other technological innovations in the complex production systems that characterize modern agriculture. However, maintaining current high yields of corn grown in the U.S. poses a serious environmental threat, due to continued overuse of water and nitrogen inputs. In order to minimize environmental damage and input costs, farmers will likely have to resort to producing corn with less irrigation water and nitrogen fertilizer in the future. This will lead to increased levels of water and nitrogen stress imposed upon the crop. To reduce over reliance on these inputs, future corn breeding efforts should focus on improving tolerance of corn to water and nitrogen stresses, utilizing appropriate plant stress tolerance mechanisms. The objective of this study was to identify appropriate stress tolerance mechanisms by characterizing the agronomic (grain yield and yield component) responses of hybrids of different eras to varying water and nitrogen supply. Twelve corn hybrids from three eras of release (1970’s, and early 1990’s and late 1990’s) were grown under deficit and adequate levels of water and nitrogen to characterize their agronomic responses to varying water and nitrogen supply. Hybrid eras did not differ in their ability to maintain grain yields under water or nitrogen stress, while individual hybrids varied. Likewise, they varied in their ability to respond to adequate water and nitrogen conditions, maximizing yields. Some hybrids were observed to yield relatively well under both deficit and adequate conditions of water or nitrogen, suggesting that it should be feasible to combine stress tolerance along with high yield potential in future elite germplasm. We found that hybrids’ possessing stress tolerance mechanisms conferring ability to maximize kernel number under stress was critical to their ability to maximize grain yields. Thus, we concluded that utilizing these mechanisms to improve stress tolerance should be a high priority of corn improvement programs.
Technical Abstract: Maintaining current high yields of corn (Zea mays L.) grown in the U.S. poses a serious environmental threat, due to continued overuse of water and nitrogen (N) inputs. To reduce over reliance on these inputs, future corn breeding efforts should focus on improving tolerance of corn to water and N stresses, utilizing appropriate stress tolerance mechanisms. The objective of this study was to identify appropriate stress tolerance mechanisms by characterizing the agronomic responses of 12 hybrids from three different eras (B73 x Mo17 from 1970’s, and 3 early 1990’s and 8 late 1990’s Pioneer Brand hybrids) to varying water and N supply. This was done by growing the hybrids under deficit and adequate levels of water (1/2 and full ET) and N (0 and 200 kg ha-1) in a four-year field study and measuring grain yield and other agronomic variables. While hybrid eras didn’t differ, individual hybrids varied in ability to maintain yields 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. Kernel number per unit area was the most highly correlated variable with grain yield (r=0.951) of all agronomic variables, indicating hybrid ability to maximize kernel number under deficit and adequate levels of water and N was critical to maximizing grain yield. Determining physiological mechanisms associated with ability to maintain kernel number under stress should be a high priority of breeding programs.