DSSAT Nitrogen cycle simulation of cover crop-maize rotations under irrigated Mediterranean conditions

14 Pags., 6 Tabls., 5 Figs.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 DSSAT-CENTURY 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.This study was supported by the Ministry of Innovation, Science, and Technology of Spain (Project no. AGL2005-08020-C05-01) and by the Qualiwater project (INCO-CT-2005-015031). M. Salmerón was granted with a J.A.E. fellowship by the CSIC.Peer reviewe