Simulating long-term impacts of winter rye cover crop on hydrologic cycling and nitrogen dynamics for a corn-soybean crop system
Dates
Year
2010
Citation
Qi, Z., Helmers, M. J., Malone, R. W., and Thorp, K. R., 2010, Simulating long-term impacts of winter rye cover crop on hydrologic cycling and nitrogen dynamics for a corn-soybean crop system: Transactions of the ASAB, v. 54, p. 1575-1588.
Summary
Planting winter cover crops into corn‐soybean rotations is a potential approach for reducing subsurface drainage and nitrate‐nitrogen (NO3‐N) loss. However, the long‐term impact of this practice needs investigation. We evaluated the RZWQM2 model against comprehensive field data (2005‐2009) in Iowa and used this model to study the long‐term (1970‐2009) hydrologic and nitrogen cycling effects of a winter cover crop within a corn‐soybean rotation. The calibrated RZWQM2 model satisfactorily simulated crop yield, biomass, and N uptake with percent error (PE) within ±15% and relative root mean square error (RRMSE) <30% except for soybean biomass and rye N uptake. Daily and annual drainage and annual NO3‐N loss were simulated satisfactorily, [...]
Summary
Planting winter cover crops into corn‐soybean rotations is a potential approach for reducing subsurface drainage and nitrate‐nitrogen (NO3‐N) loss. However, the long‐term impact of this practice needs investigation. We evaluated the RZWQM2 model against comprehensive field data (2005‐2009) in Iowa and used this model to study the long‐term (1970‐2009) hydrologic and nitrogen cycling effects of a winter cover crop within a corn‐soybean rotation. The calibrated RZWQM2 model satisfactorily simulated crop yield, biomass, and N uptake with percent error (PE) within ±15% and relative root mean square error (RRMSE) <30% except for soybean biomass and rye N uptake. Daily and annual drainage and annual NO3‐N loss were simulated satisfactorily, with Nash‐Sutcliffe efficiency (NSE) >0.50, ratio of RMSE to standard error (RSR) <0.70, and percent bias (PBIAS) within ±25% except for the overestimation of annual drainage and NO3‐N in CTRL2. The simulation in soil water storage was unsatisfactory but comparable to other studies. Long‐term simulations showed that adding rye as a winter cover crop reduced annual subsurface drainage and NO3‐N loss by 11% (2.9 cm) and 22% (11.8 kg N ha‐1), respectively, and increased annual ET by 5% (2.9 cm). Results suggest that introducing winter rye cover crops to corn‐soybean rotations is a promising approach to reduce N loss from subsurface drained agricultural systems. However, simulated N immobilization under the winter cover crop was not increased, which is inconsistent with a lysimeter study previously reported in the literature. Therefore, further research is needed to refine the simulation of immobilization in cover crop systems using RZWQM2 under a wider range of weather conditions.