DSSAT nitrogen cycle simulation of cover crop-maize rotations under irrigated mediterranean conditions

The accurate simulation of N cycle in winter cover crop-maize rotations can help to study management practices aimed at reducing N leaching. A lysimeter and field experiment were used to calibrate and test the model under irrigated Mediterranean conditions. Thereafter, the model was used to evaluate the impact of cover crop-maize rotations on N leaching for a range of soil types and irrigation managements during a 14 yr rotation in La Violada watershed, Spain. The Decision Support System for Agrotechnology Transfer (DSSAT) v4.5.0.51 soil temperature subroutine overpredicted soil temperature, but this was improved when using a new EPIC-based soil temperature subroutine that will be available in DSSAT v4.6. The model was accurate simulating total maize N content in maize after fallow and after different cover crops (root mean square error [RMSE] = 25 kg N ha^-1), adequately simulated N leaching reductions with cover crops, and was less efficient simulating soil inorganic N. Overall, the DSSATCENTURY model proved appropriate to simulate N cycle. DSSAT-CERES-Maize did not adequately simulate the observed yield reduction under N limitation in our high yielding conditions. Simulations in La Violada watershed indicate that N leaching in maize would still be high (44-98 kg N ha^-1 yr^-1) under an optimized water and N management. Cover crop-maize rotations could reduce N leaching by 31% while supplying similar N availability to maize than fallow-maize rotations. The model was useful to study several management scenarios that would be difficult to investigate under field conditions.