EPIC model prediction of winter rye cover crop effects on crop yield and nitrate‐N leaching in Minnesota

Abstract Coarse‐textured soils in central Minnesota cultivated with corn ( Zea mays L.) and soybean ( Glycine max L.) exhibit good productivity, however, are vulnerable to nitrate‐N leaching losses. In such circumstances, winter rye ( Secale cereale L.) as a cover crop may reduce nitrate‐N leaching by scavenging soil nitrogen (N) in late‐fall and early‐spring fallow period. The Environmental Policy Integrated Climate (EPIC) model was used for decadal‐scale (2010–2020) simulation of yield/biomass and nitrate‐N leaching in corn– (C–C) and corn–soybean/soybean–corn (C–Sb/Sb–C) rotations, with and without winter rye, under different fertilizer N rates applied to corn (0, 100, 200, 250, and 300 kg ha −1 ) on irrigated coarse‐textured soils in central Minnesota. Model efficiency calculated based on Nash–Sutcliffe coefficient, relative root mean square error, and R 2 statistics indicate that EPIC assessment for calibration and validation treatments was excellent‐good for corn/soybean yield, and good‐satisfactory for rye biomass and NO 3 ‐N leaching losses. Results indicate that N fertilizer rates up to 250 kg N ha −1 applied to corn had a positive impact on rye biomass; however, large crop‐rotation and climate‐induced variations were observed. Annual nitrate‐N leaching losses at maximum return to nitrogen rates at a 0.05 N price to crop value ratio for corn under C–C (250 kg N ha −1 ) and C–Sb/Sb–C (200 kg N ha −1 ) with no‐rye averaged 61.5, 47.4, and 41.8 kg ha −1 , while grain yield averaged 12.5, 12.3, and 4.0 t ha −1 for corn (C–C), corn (C–Sb/Sb–C), and soybean (C–Sb/Sb–C), respectively. Planting rye under these rotations gave annual average reductions in nitrate‐N losses relative to corresponding no‐rye treatments of 2.9 (4.7%), 3.4 (7.3%), and 6.5 kg ha −1 (15.6%), with rye N uptake of 10.3, 12.1, and 33.5 kg ha −1 ; and rye biomass production of 0.61, 0.74, and 2.0 t ha −1 , respectively. EPIC assessment indicates that winter rye as cover crop did not negatively impact the subsequent corn/soybean yield and proved to be an effective strategy for reducing nitrate‐N losses, particularly following the soybean crop.