Winter Rye Reduces Nitrate Loss to Subsurface Drainage - Model (RZWQM) Comparison to Long Term Field Data.

The corn-soybean crop rotation ubiquitous in the Midwest USA leaks nitrogen to surface waters partly because of the absence of living plants for several months of the year. Using a winter rye cover crop (CC) has shown promise to take up soil nitrogen (N), thus reducing nitrate concentrations in tile drainage. However, the benefits are variable based on local management, climate, and soil. A well tested model would help quantify the effects of CC under the variety of expected conditions. Our objective was to test the Root Zone Water Quality Model (RZWQM) for CC growth and its effect on tile drainage N loss using long-term (9-year; 2002-2010) field data. The model was calibrated for hydrology, nutrients, and main crop yield using a control treatment with no winter cover crop (NCC). Literature-derived and default parameters were used to predict CC biomass for a corn-rye-soybean-rye rotation on the same group of experimental plots and on nearby fields. The preliminary results suggest that the calibrated model was effective at predicting rye cover crop growth and the nitrate-reducing benefits of a winter rye cover crop in a corn-soybean rotation.