Application of the DNDC model to tile-drained Illinois agroecosystems: Model comparison of conventional and diversified rotations

Using the DeNitrification-DeComposition (DNDC) model we compare conventional, fertilizer-driven corn-soybean rotations to alternative management scenarios which include the management of cereal rye cover crops and corn-soybean-wheat-red clover rotations. We conduct our analysis for tile-drained, silty clay loam soils of Illinois. DNDC simulations suggest that, relative to conventional rotations, a nitrate leaching reduction of 30-50% under corn and of 15-50% under soybean crops can be achieved with diversified rotations, an outcome which corroborates results from a quantitative literature review we previously conducted using a meta-analysis framework. Additionally, over a 10-year simulation, legume-fertilized systems are predicted to result in 52% lower N₂O gas flux relative to fertilizer-driven systems. We identify soil organic carbon storage, legume N-fixation rate, and cereal rye cover crop growth as areas requiring further development to accurately apply DNDC to diversified cropping systems. Overall, DNDC simulation suggests diversified rotations that alternate winter and summer annuals have the potential to dramatically increase N retention in agroecosystems.