Evaluating precision irrigation and nitrogen management for corn using SWAP model under changing humid climates

Climate change is expected to alter crop productivity and nitrogen dynamics, yet limited research has quantified how different irrigation strategies can mitigate these impacts, particularly in humid regions where erratic rainfall complicates water and nutrient management. This study employs the agro-hydrological model SWAP to examine the performance of rainfed, calendar, and precision irrigation with both single (1 N) and split (2 N) nitrogen applications. SWAP model calibration and evaluation were conducted using observed volumetric water content across multiple soil depths as well as nitrate concentration data. Corn yield, nitrogen uptake, nitrate leaching, and irrigation water productivity were compared for each integrated irrigation and nitrogen strategy under different climate scenarios. To distinguish the effects of irrigation and nitrogen application strategy, precision irrigation was simulated using both a single nitrogen application (Precision-1N) and a split application (Precision-2N). Results indicated that nitrogen application timing (1 N vs. 2 N) had less of an impact on yields, leaching, and water productivity compared to irrigation strategy. Precision-2N consistently outperformed the Calendar-1N system across all scenarios, with higher yields and nitrogen uptake, and significantly better water productivity. The greatest long-term benefits of the Precision-2N treatment compared to Calendar-1N were observed under Scenario 4, which featured increased rainfall variability without an increase in total precipitation. In contrast, the smallest disparities between the irrigation treatments were observed in climate scenarios where precipitation increased. An analysis of interannual variability demonstrated that the Precision-2N benefits were most pronounced during years with frequent extreme temperature events. These findings reinforce the effectiveness of Precision-2N to achieve a favorable balance between higher yields and reduced NO₃ leaching.