Quantifying the impact of 4 R nutrient stewardship and cover cropping on soil health across the U.S. Corn Belt

The adoption of the “4 R” Nutrient Stewardship framework in crop production has been increasing over the last decade. However, studies evaluating how these practices affect both agronomic outcomes and soil health across various environments in the United States (U.S.) Corn Belt are limited. With a network of coordinated studies in the major corn ( Zea mays L.)-producing region of the U.S., we evaluated changes in soil health indicators in Mollisols and Alfisols over four years of 4 R management with and without a cover crop, as compared to the prevailing practice used by farmers in the region, and/or a system without nitrogen (N) fertilization. Soil properties were determined in 2017 and 2020 at 0–15 cm depth. Eight soil health indicators were individually scored using the Soil Management Assessment Framework (SMAF) curves and integrated into an overall Soil Health Index (SHI). After four years of implementation, 4 R practices combined with cover crops improved soil health indicators and overall soil health compared to 2017 (up to a 16% increase in SHI). In contrast, the other treatments (without cover cropping) only led to small changes in SHI after four years. The scores with higher sensitivity to these cropping systems were those related to physical properties and soil organic carbon. Changes in SHI were not correlated with corn yields. This study provides one of the first coordinated, multi-site evaluations integrating 4 R nutrient stewardship, cover cropping, and soil health assessment through SMAF-based indices, demonstrating that short-term improvements in overall soil health are primarily driven by the inclusion of cover crops (4 R management combined with cover cropping) rather than 4 R nutrient management alone.