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

Abstract

Abstract 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.