Short-term corn yield response associated with nitrogen dynamics from fall-seeded cover crops under no-till dryland conditions

Authors: CHIM, BEE KHIM - University Of Maine; Osborne, Shannon; Lehman, R - Michael

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2022
Publication Date: 9/8/2022
Citation: Chim, B., Osborne, S.L., Lehman, R.M. 2022. Short-term corn yield response associated with nitrogen dynamics from fall-seeded cover crops under no-till dryland conditions. Agrosystems, Geosciences & Environment. 5(3). Article 320305. https://doi.org/10.1002/agg2.20305.
DOI: https://doi.org/10.1002/agg2.20305

Interpretive Summary: The availability of in-season nitrogen to corn following fall-seeded cover crops depends on seasonal patterns of nitrogen transformations that are site- and year-dependent and resist prediction. Our research focused on evaluating nitrogen dynamics following different cover crops (legume, non-legume, none) and their effect on following corn yields within an established no-till winter wheat-cover crop/corn-soybean rotation. A field experiment was conducted over two site-years in adjacent locations for two consecutive growing seasons in the U.S. northern plains. Fall cover crop treatments were sweet clover, winter cereal rye, hairy vetch and no cover crop. Spring cover crop biomass and nitrogen uptake, in situ soil nitrogen mineralization following cover crop termination, and subsequent corn yield and nitrogen uptake were measured. Legume cover crops were associated with higher corn yields while rye cover crops did not significantly decrease yields, despite nitrogen immobilization by a large rye cover crop in one year. Legume cover crops produced the highest rates of nitrogen mineralization during periods of high nitrogen demand by corn (V6 – R3) and the highest seasonal amounts of mineralized nitrogen compared to rye or no cover crops. These measurements better predicted yields across all treatments compared to other approaches. Lower apparent nitrogen use efficiency observed with the legume treatments is an indicator that less fertilizer nitrogen can be applied in the growing season following legume cover crops.

Technical Abstract: The availability of in-season N to corn following fall-seeded cover crops depends on seasonal patterns of N transformations that are site- and year-dependent and resist prediction. Our objectives were to evaluate N dynamics following different cover crops (legume, non-legume, none) and their relationship with subsequent corn yields within an established no-till winter wheat (Triticum aestivum L.) - cover crop/corn (Zea mays L.) - soybean (Glycine max) rotation over two site-years in the U.S. Northern Plains. Spring cover crop biomass and N uptake, in situ soil N mineralization following cover crop termination, and corn grain yield and N uptake were measured. Legume cover crops were associated with higher corn yields while rye (Secale cereale) did not significantly decrease corn yields, despite N immobilization by a large rye cover crop in one year. Legume cover crops produced the highest rates of N mineralization during periods of high N demand by corn (V6-R3) and the highest seasonal amounts of mineralized N compared to rye or no cover crops. In-situ N mineralization measurements better predicted yields across all treatments compared to approaches using cover crop biomass and N content. In situ N mineralization rates during corn growth stages V6-R3 provided a superior prediction (r = 0.83) of corn yields compared to all seasonal estimates of N provided by cover crops. Lower apparent N use efficiency (NUE) calculated with contributions of in-season N mineralization indicated that less fertilizer N can be applied in the growing season following legume cover crops.