CSM‐IXIM: A New Maize Simulation Model for DSSAT Version 4.5

The CERES‐Maize model is the most widely used maize (Zea mays L.) model and is a recognized reference for comparing new developments in maize growth, development, and yield simulation. The objective of this study was to present and evaluate CSM‐IXIM, a new maize simulation model for DSSAT version 4.5. Code from CSM‐CERES‐Maize, the modular version of the model, was modified to include a number of model improvements. Model enhancements included the simulation of leaf area, C assimilation and partitioning, ear growth, kernel number, grain yield, and plant N acquisition and distribution. The addition of two genetic coefficients to simulate per‐leaf foliar surface produced 32% smaller root mean square error (RMSE) values estimating leaf area index than did CSM‐CERES. Grain yield and total shoot biomass were correctly simulated by both models. Carbon partitioning, however, showed differences. The CSM‐IXIM model simulated leaf mass more accurately, reducing the CSM‐CERES error by 44%, but overestimated stem mass, especially after stress, resulting in similar average RMSE values as CSM‐CERES. Excessive N uptake after fertilization events as simulated by CSM‐CERES was also corrected, reducing the error by 16%. The accuracy of N distribution to stems was improved by 68%. These improvements in CSM‐IXIM provided a stable basis for more precise simulation of maize canopy growth and yield and a framework for continuing future model developments.