Soil nitrogen dynamics and crop yield responses to diverse cover crop mixtures in a rainfed corn‐based cropping system in Nebraska

Résumé fourni par la source

Abstract This study evaluated the effects of mixed cover crop (CC) species on biomass production, nitrogen (N) uptake, soil N dynamics, and crop performance in a rainfed corn ( Zea mays L.)–soybean ( Glycine max L.) and continuous corn system in eastern Nebraska from 2021 to 2023. Four treatments—cereal rye, mixture‐1 (cereal rye, winter pea, and triticale), mixture‐2 (barley, Kura clover, and canola), and a no‐cover control—were fall‐seeded each year. Due to below‐average precipitation, CC establishment was poor, resulting in low biomass (<0.2 Mg ha −1 ) and modest N uptake (4.1 kg N ha −1 ). Consequently, CC species did not significantly affect spring soil nitrate (NO 3 –N) or ammonium (NH 4 –N) concentrations across crop phases. Cropping year showed a strong influence on soil NH 4 –N, with concentrations markedly higher in 2023 than in 2022. Cereal rye exhibited a higher residue C:N ratio and contributed to increased residual fall soil NO 3 –N and NH 4 –N in upper soil layers (0–15 cm), suggesting slow biomass decomposition and potential late‐season N release. Neither crop rotation nor CC treatment significantly influenced corn or soybean yields, consistent with limited CC biomass production. Favorable weather in 2023 improved corn N uptake and yield. Corn–soybean rotation enhanced corn vigor (normalized difference vegetation index [NDVI]), and CC mixtures improved soybean NDVI over cereal rye. Grain yields correlated with NDVI but not with CC biomass or N uptake, highlighting the limitations of CCs under dryland conditions. Overall, drought‐limited CC growth constrained N scavenging and yield benefits, underscoring the importance of environment‐specific CC management in rainfed agroecosystems.

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