Testing and improving the maize models in DSSAT: Development, growth, yield, and N uptake

The DSSAT (Decision Support System for Agrotechnology Transfer) is the most widely used model package to characterize growth, development, yield, and N uptake of multiple crop species. The objectives of this study were: 1) to evaluate the performance of the maize (Zea mays L.) models CSM-CERES and CSM-IXIM available in DSSAT version 4.5, when simulating high yield conditions, 2) to test the IXIM model with an alternative approach to estimate crop N demand, based on Plénet and Lemaire (2000), and 3) with this alternative approach, examine some options to simulate grain N concentration. The two models were evaluated with data collected from two experimental fields in Almacelles, Spain, during three consecutive years under various N management treatments, combining fertilization and residue handling. Fertilization treatments included two doses of mineral fertilizer: 300 kg N ha−1 (N300), along with a N-free fertilized control (N0). Crop residues were either removed (R) or incorporated (I). The grain yields obtained in the fields (14% moisture) varied, depending on the N fertilization, from 11 to 20 Mg ha−1. In our high yielding irrigated maize conditions, both models were able to simulate grain yield and biomass accurately, with RRMSE of 9.5 and 11.4% for CERES and 14.9 and 14.3% for IXIM respectively. Estimations of N uptake were also accurate, with RRMSE of 12.0 and 8.6% for CERES and IXIM. The IXIM model with the alternative approach to estimate crop N demand simulated grain yield and crop N uptake better than the IXIM with the current approach based on Jones (1983). The RMSE was reduced by 22% for yield and by 55% for biomass, while the simulated N uptake reduced the RMSE by 12%. With this alternative approach, the best grain N simulations were obtained with a modification of the Ciampitti and Vyn (2013) function.