Simulating the impact of conservation agriculture on corn yield in the Philippines using the DSSAT CERES-Maize model.

The study predicted the effect of conservation agriculture on corn yield in the Philippines using the Decision Support System for Agrotechnology Transfer (DSSAT) Ceres-Maize crop model. The model was calibrated and validated using crop, soil and weather data obtained from an experimental site in Claveria, Misamis Oriental, Philippines under conservation agriculture production system (CAPS) and conventional plow-based system. An optimized step-wise procedure was used in model calibration by setting up boundaries for each coefficient and specifying a constant interval for each coefficient. Model validation showed a reasonably fair to good match between observed and simulated values of silking and maturity dates, maximum leaf area index (LAI), yield and above-ground biomass as indicated by the various statistical criteria such as root mean square error (RMSE), relative root mean square error (RRMSE) and Nash-Sutcliffe model efficiency (NSE) for both production systems. Model simulations were consequently performed under scenarios of changing soil organic carbon (SOC) and total soil nitrogen (TN) of up to +/- 30% on both variables. Simulation results showed that the highest positive percent relative change in crop yield was 5.5% to 10.2% under a scenario of 30% increase in both SOC and TN. For the plow-based system, simulation results showed that the highest negative percent change in yield was 24.4% to 28.5% under a scenario of 30% decrease in both SOC and TN. These simulation results suggest that long-term practice of conservation agriculture production system would lead to corn yield being comparable with or better than that under conventional plow-based system. In contrast, long-term practice of conventional plow-based system would result in reduced corn yield and decreased profits for upland corn farmers.