Winter cover crops, like cereal rye ( Secale cereale ), are one of the most promising solutions to environmental sustainability in the maize ( Zea mays L.)-soybean ( Glycine max L. merr.) cropping systems of the Midwestern US. However, one of the largest barriers to adoption is the “yield drag,” or decrease in cash crop yield that occurs when following cereal rye (especially with maize). Reports of maize yield drag are inconsistent, and the underlying mechanisms are unclear. Our primary research questions were: i. Does fertilizer N alleviate maize yield drag? ii. does hillslope position change soil N dynamics and maize N needs after cereal rye cover crop? iii. what factors across site-years and hillslopes best predict maize yields? We conducted a split-plot experiment cover/no-cover × six nitrogen (N) rates across three hillslope positions (summit, backslope, and toeslope) over three site-years. Fertilizer N rates ranged from 0 to 336 kg N ha −1 . In response, we measured soil N dynamics (net N mineralization, inorganic and organic N pools), crop grain yield, and response to N fertilizer. We also ran a random forest model to identify the most important factors affecting yield drag. There were few, weak interactive effects of hillslope position and cover crops on soil N dynamics. Toeslope positions tended to increase soil N pools. Cover crops had weaker effects on soil N dynamics but did decrease soil nitrate by 26%, on average, across the field. There were more complex hillslope × cover crop interactions on maize yield response to N fertilizer. While fertilizer N partially alleviated maize yield drag, yields remained consistently lower under cover crops compared to winter fallow, particularly at summit and backslope positions characterized by lower soil organic matter (SOM). Random forest modeling identified N application rate, cereal rye biomass, soil test phosphorus, and SOM as key predictors of maize yield, and revealed complex interactions between management and hillslope factors (i.e., soil properties). Our findings emphasize the importance of considering landscape variability when optimizing N management in cereal rye-maize systems to mitigate yield penalties and enhance nutrient use efficiency. The soil variation that comes from hillslope positions has complex interactions with cover crops and fertilizer N. These interactions need to be considered, and managed appropriately, to ensure farmers have reliable maize crop yields when following a cereal rye winter cover crop. • Hillslope position strongly regulates soil organic and inorganic N pools and maize N needs. • Cereal rye reduces inorganic soil N and causes consistent maize yield drag that is not fully reversed by fertilizer N. • Soil test P and organic matter are important factors regulating maize yield. • Precision management and conservation are key to reliable yields and efficient N fertilizer use.
Pessotto et al. (2026) studied this question.