Parameterizing the cereal rye crop in SWAT model and evaluating its impact in watershed scale simulations

Cover crops, such as cereal rye, are expected to improve the ecosystem services such as water productivity, nutrient/radiation use efficiency, water quality improvement etc. if included in the conventional cropping system of maize-soybean rotations in the Midwest USA. The introduction of cereal rye during the fall/winter can also potentially alleviate food vs biofuel concerns and improve the diversity in the cropping systems. While, there are many plot scale experimental studies documenting the benefits of the cereal rye cover crop, only a few studies have evaluated its benefits at the watershed scale. One of the plausible reason for such limited studies is the inadequate parameterization of the cereal rye crop in the watershed scale models such as Soil and Water Assessment Tool (SWAT). In this study, experimental data such as leaf area index, biomass production, and nutrient uptake are collected during the various crop growth stages of cereal rye crop grown in continuous maize and maize-soybean rotation. The data collected at the Water Quality Field Station in Indiana is utilized for suggesting the crop growth parameter ranges. The parameterized model is evaluated by comparing the measured and simulated biomass yield, leaf area index and nutrient losses from the experimental plots. The parameterized model is used to evaluate the watershed scale impacts of the proposed cropping system. The results of the study indicate that the suggested crop growth parameters are acceptable and indicate satisfactory simulation of the cereal rye crop. The watershed scale simulation of the suggested cropping pattern indicate that the cover cropping has the scope to reduce the nutrient loadings from the Midwest USA.