Determination of a Sustainable Management for Rice Production Through a Modeling Approach

Crop models have been designed to capture agronomic and environmental variables. Irrigation and nitrogen (N) application are critical factors in agroecosystems for achieving adequate yield, while poor management strategies not only make the environment vulnerable, but waste the inputs. We parametrized and evaluated the APSIM-Oryza model using a two-year experiment under various irrigation techniques (continuous flood (CF) and alternate wetting and drying (AWD)) and N levels (25, 50, and 100% of the recommended N levels). The model demonstrated a reasonable fit between simulated and observed aboveground biomass, leaf area index, total N uptake, and grain yield regarding to higher model efficiency values (EF > 71). APSIM-Oryza acceptably simulated the rice yield over parametrization (R2 = 0.97, RMSE = 213 kg ha- 1) and evaluation (R2 = 0.92, RMSE = 307 kg ha- 1). Consequently, two scenarios were run based on historical weather data. Scenario analysis exhibited that the lowest simulated yield and N use efficiency (NUE) were obtained with the basal N application, whereas the split-N application ratio (SNR) promoted the simulated yield and NUE by improving the total N uptake. Water productivity (WP) improved by 15-32% without yield loss under AWD irrigation. According to the simulation results, the optimal modeled yield, total N uptake, NUE, and WP were achieved by combining SNR 5:5 under AWD. Still, the N level was affected by environmental factors (80.5 kg N ha- 1 at Sari and 57.5 kg N ha- 1 at Babolsar and Nowshahr). Thus, it can be concluded that the modeling approach can be a low-cost and labor-saving practice to evaluate the stability in a district over a long-term period instead of on-farm experiments. Nevertheless, a thorough agroecological assessment in the model requires either a reliable or multiple databases for precise calibration and accurate evaluation to consider all aspects of ecology and agronomy.