Modelling crop growth and soil hydrothermal regimes under conservation agriculture using APSIM-wheat

With increasing adoption of residue retention over soil surface, there is an urgent need to investigate the effect of residue on soil water moderation and soil temperature distribution during crop growth period. Therefore, an investigation was carried out on wheat crop, grown under long term experiment integrating a dual strategy of field experiment and crop simulation modelling. The major aim of the present study was to simulate the conservation agriculture effects on soil water profile and soil thermal regime in wheat crop under maize based cropping system using APSIM-Agriculture Production System Simulator) model. The experiment followed a split plot design with three replications, evaluating two tillage practices: zero tillage with residue retention (ZT + R) and conventional tillage with residue incorporation (CT + R). . The APSIM model was calibrated using measured data from the 2018-19 cropping season and validated with independent datasets from 2019-20. Model performance was rigorously evaluated using statistical metrics such as the coefficient of determination (R²), root mean square error (RMSE), normalized RMSE (nRMSE), Willmott's index of agreement (D-index), and mean bias error (MBE). The results indicated that the model accurately simulated crop phenology, leaf area index, aboveground biomass, and grain yield under both tillage treatments. Results of validation of APSIM model showed good agreement for simulated soil temperature (RMSE = 1.12-1.87 °C, nRMSE = 0.08-0.12 and R² = 0.67-0.71) and soil water (RMSE = 0.017-0.031 cm³cm^-3, nRMSE = 0.07-0.13 and R² = 0.66-0.80) in both CT + R and ZT + R treatments. Simulated soil water content (SWC) was lower in the CT + R treatment compared to ZT + R. The model simulated transpiration and drainage were higher under ZT + R, whereas evaporation was greater in CT + R, reflecting the influence of residue management and tillage on soil moisture dynamics. APSIM showed that the soil temperature was more in CT + R than ZT + R for 0-60 cm soil depth. Additionally, diurnal fluctuations in soil temperature were more pronounced in the surface layer (0-15 cm) than in the deeper layer (45-60 cm) under both treatments. The analysis demonstrated the capabilities of APSIM to capture the effect of tillage practices and cropping system on soil water profile, temperature changes and crop growth.