Summer legumes following winter wheat boost soil nitrogen availability and corn yield

Efficient nitrogen (N) management is critical for improving nitrogen use efficiency (NUE) and sustaining corn ( Zea mays L.) yields. We evaluated summer cover crops planted after winter wheat ( Triticum aestivum L.) to quantify biomass, N content, soil N dynamics, and subsequent corn performance under rainfed conditions in eastern Nebraska. Across 2 site‐years (2020–2021 and 2023–2024), eight CC treatments were tested, including six legumes, one grass, one legume mixture, and two no‐CC controls. Cover crop biomass ranged from 760 kg ha −1 (cereal rye ( Secale cereale L.), Austrian winter pea ( Pisum sativum arvense L.)) to 8630 kg ha −1 (sunn‐hemp ( Crotalaria juncea L.), legume mixture). Hairy vetch ( Vicia villosa L.) and soybean ( Glycine max (L.) Merr.) had high biomass N accumulation (176 and 188 kg N ha −1 , respectively) due to biological N‐fixation. Hairy vetch significantly increased soil nitrate‐N availability by 154% (preplant) and 111% (in‐season) compared to the no‐N and cereal rye controls. Corn yield improved significantly ( p < 0.001) following legume CCs, with hairy vetch, sunn‐hemp, and forage‐pea ( Pisum sativum L.) outperforming other species. Legumes increased corn yield by 2.50 Mg ha −1 (2021) and 2.23 Mg ha −1 (2024) compared to the N control treatment, contributing 29 and 44 kg ha −1 of grain N, respectively. Apparent N credits from legumes ranged from 32 to 99 kg N ha −1 . In contrast, cereal rye reduced yield and N uptake, indicating net N immobilization. These results support legume CCs as a viable strategy to enhance NUE in rainfed corn systems.