Combining tillage and nitrogen practices to optimize soil nitrogen dynamics and wheat yield across various soil textures, using RZWQM2

The optimal combination of tillage and nitrogen practices could be an effective strategy for improving crop yields and mitigating soil nitrogen loss. This study aimed to identify the optimal combination of field management practices for controlling soil nitrogen distribution and enhancing wheat yield across various soil textures in the semi-arid region of Iraq, using agricultural modeling. The Root Zone Water Quality Model (RZWQM2) was calibrated and validated using experimental field data from the 2023 and 2024 wheat-growing seasons. Various modeling scenarios were then created to evaluate and determine the optimal combination of tillage practices (deep tillage and shallow tillage) with nitrogen fertilization rates (100 and 250 kg N/ha) for sandy clay and silty clay soils. The model was successfully calibrated and validated with an accepted range of statistical indicators. Simulation results indicated that both soil textures presented comparable responses to all management practices. Simulation results indicated that, deep tillage practice reduced soil nitrate leaching and N 2 O emissions by an average of 0.04 μg/cm 2 and 0.27 kg/ha, respectively, while increasing nitrate retention in the soil profile and wheat production by an average of 0.05 and 0.03 kg/ha, respectively, compared to shallow tillage. Applying 250 kg N/ha increased soil nitrate flux and N 2 O emissions, particularly when combined with shallow tillage. Therefore, combining deep tillage with nitrogen application rates is the optimal field management approach and is suggested for both soil textures, as it minimizes soil nitrogen loss and enhances wheat productivity. • Combining deep tillage with N rates improves field productivity more than shallow tillage. • Sandy clay and silty clay soils showed comparable responses to combined field practices. • Deep tillage showed better results of crop yield and soil nitrogen compared to shallow tillage.