Winter wheat residue management alters corn growth, grain yield, nitrogen requirement, soil nitrate-nitrogen, and farm profit

Context Winter cereal cover crops are effective in reducing nitrate-nitrogen (NO 3 -N) leaching from corn ( Zea mays L.) grown in rotation with soybean ( Glycine max L.), yet how wheat ( Triticum aestivum L.) cover crop management interacts with N fertilizer rates to influence corn yield, N requirements, soil NO 3 -N dynamics, and farm profitability remains poorly understood. Objectives This study aimed to quantify the effects of wheat cover crop management on corn growth, grain yield, economic optimum N rate (EONR), end-of-season soil NO 3 -N, and profitability across a wide range of N fertilizer inputs. Methods A four-year field experiment (2018–2021) was conducted using a randomized complete block design with a split-plot arrangement and four replicates. Main plots consisted of four cover crop treatments: fallow (no cover crop), early terminated wheat (ET; four weeks before corn planting), late terminated wheat (LT; at corn planting), and harvested wheat with residue removal (RR). Subplots included six to seven N fertilizer rates (0–336 kg N ha −1 ). Results Delayed termination increased wheat aboveground and belowground biomass and C:N ratios, with belowground C:N ratios averaging 1.5-fold greater than aboveground. Cover crop management strongly influenced corn grain yield and N requirement. Averaged across years, EONR was 208, 219, 251, and 209 kg N ha −1 and corresponding yields at EONR were 13.45, 11.34, 11.43, and 9.65 Mg ha −1 for fallow, ET, LT, and RR, respectively. Nitrogen application beyond EONR substantially increased end-of-season soil NO 3 -N across all treatments, suggesting a greater potential for NO 3 -N leaching. While fallow achieved the highest yields, it also produced the greatest residual soil NO 3 -N. Wheat cover crop treatments, particularly LT, buffered NO 3 -N accumulation when N inputs exceeded crop demand. Conclusions These results highlight the importance of targeting EONR to balance productivity and environmental protection in corn systems. Early-terminated wheat (average EONR = 219 kg N ha −1 ) is recommended for optimizing agronomic performance, whereas LT wheat (average EONR = 251 kg N ha −1 ) is recommended for minimizing residual soil NO 3 -N and potential environmental N losses. Therefore, EONR should be adjusted according to wheat cover crop management to optimize both economic and environmental outcomes.