Evaluation of nitrogen loss reduction strategies using DRAINMOD-DSSAT in east-central Illinois

Agricultural system modeling has become an effective tool for analyzing and quantifying the effects of varying management practices and environmental conditions on crop production and nutrient export from croplands. The use of such modeling tools provides useful insights in identifying the most effective management practices for enhancing productivity, sustainability, and resiliency of agricultural systems. This study focuses on testing and application of an integrated field-scale process-based model, DRAINMOD-DSSAT, for simulating hydrology, nitrate-nitrogen (NO₃-N) loss, and crop growth and yield responses in artificially drained croplands. The tested model was used to evaluate the effects of different N fertilizer application rates and timings in both conventional and controlled drainage conditions on crop yield and NO₃-N losses in a poorly drained Drummer-Flanagan soil in east-central Illinois. The model was calibrated and validated for a corn [Zea Mays L.] – soybean [Glycine Max (L.)] rotation using 7 years (1992–1998) of field-measured tile drainage, crop yield, and NO₃-N data. The graphical and statistical evaluations indicated very good model performance. Specifically, monthly tile drainage flow was predicted with modeling efficiency (NSE), index of agreement (d), and mean absolute error (MAE) of 0.85, 0.96, and 0.69 cm, respectively. Monthly NO₃-N losses were predicted with NSE, d, and MAE of 0.82, 0.95, and 1.16 kg N ha⁻¹, respectively. Corn and soybean yields were predicted with an absolute percent error (PE) of 1.84 and 12.07, respectively. The long-term model simulation results indicated that split N application of 50 % during spring-pre plant (S) and 50 % during side-dressing (SD) could increase crop yield and reduce N leaching losses compared to other tested N application methods: spring (S) only, fall-spring split (F-S), and fall-spring-side-dressing (F-S-SD). Further, applying 10 % and 20 % reduced N rates (194 kg N ha⁻¹ and 174 kg N ha⁻¹, respectively) in combination with S-SD split application in controlled drainage (CD) condition could reduce N leaching losses by 30 % and 33 %, respectively compared to the conventional application method. This study explored the effects of N fertilizer management on crop yield and nitrogen losses under two drainage conditions, and underscored the importance of N fertilizer application rates and timings for achieving yield goals while minimizing nitrogen export from drained agricultural fields. The results of the model simulations will be useful for stakeholders and policy makers while making decisions regarding promotion and adoption of best management practices for drained agricultural landscapes.