Assessing the Impact of Organic-Inorganic Nitrogen Application on Maize Yield and Nitrogen Leaching Using the DNDC Model

Abstract

In order to optimize maize yield and minimize nitrogen leaching, field experiments and DNDC model simulations assessed various organic-inorganic nitrogen application treatments. Trials were conducted in the Hetao irrigation area of Inner Mongolia, comparing six treatments: no nitrogen (CK), solely inorganic nitrogen (U1), and combinations where 25%, 50%, 75%, and 100% of inorganic nitrogen was replaced with organic nitrogen (U3O1, U1O1, U1O3, O1). The DNDC model was calibrated using the U1 treatment data from 2018-2020 and validated with other treatments. Results indicated the model accurately simulated maize yield (NRMSE < 5°%) and nitrate nitrogen leaching (NRMSE < 15%). Simulation outcomes demonstrated that increasing inorganic nitrogen application reduced crop yield and significantly increased nitrate leaching. Conversely, higher proportions of organic nitrogen, along with adjusted irrigation and frequency of inorganic nitrogen fertilization, increased maize yield while reducing nitrate leaching. At a fixed nitrogen application rate of 240 kg hm−2, maize yield initially rose and then declined with increasing organic nitrogen ratios, while nitrate nitrogen leaching decreased consistently. Optimal results were achieved with a 3:2 ratio of organic to inorganic nitrogen, yielding 12578 kg hm−2 with nitrate nitrogen leaching at 15.7 kg NO-3-N hm−2, indicating this ratio as the preferred method for combined nitrogen application in the region.