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

The availability of in-season N to corn (Zea mays L.) following fall-seeded cover crops depends on seasonal patterns of nitrogen (N) transformations that are site- and year-dependent and resist prediction. Our objectives were to evaluate N dynamics following different cover crops (legume, nonlegume, none) and their relationship with subsequent corn yields within an established no-till winter wheat (Triticum aestivum L.)-cover crop/corn-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, whereas 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 with rye or no cover crops. In-situ N mineralization measurements better predicted yields across all treatments compared with approaches using cover crop biomass and N content. In situ N mineralization rates during corn growth stages V6-R3 provided a superior prediction (r = .83) of corn yields compared with all seasonal estimates of N provided by cover crops. Lower apparent N use efficiency calculated with contributions of in-season N mineralization indicated that less fertilizer N can be applied in the growing season following legume cover crops.

Automated summary

The study examined the effects of different cover crops on corn yields and found that legume cover crops increased corn yields, while rye cover crops did not significantly decrease corn yields. Legume cover crops provided higher rates of nitrogen mineralization during the corn growing stage and higher seasonal amounts of mineralized nitrogen compared to rye or no cover crops.