Effect of Conventional Nitrogen Fertilization on Methane Uptake by and Emissions of Nitrous Oxide and Nitric Oxide from a Typical Cropland During a Maize Growing Season

Conventional nitrogen fertilization in a maize cropping system enhances the soil’s methane (CH4) sink but exacerbates emissions of nitrous oxide (N2O) and nitric oxide (NO). This study demonstrates that conventional nitrogen application (UN) increased CH4 uptake by 154%, while elevating N2O and NO emissions by 190% and 301%, respectively, compared to zero nitrogen plots (N0). Fertilization fundamentally reconfigured the regulatory mechanisms governing gas fluxes: under UN, fluxes were controlled by a complex interplay of nitrogen substrates, carbon availability, moisture, and temperature, whereas under N0, CH4 uptake exhibited significantly enhanced temperature sensitivity (with Q10 increasing from 1.06 to 7.54) and nitrogen oxide emissions became more dependent on native ammonium and extractable organic carbon. Crucially, nitrogen withdrawal reduced soil ammonium by 37.1% without altering non-nitrogen soil properties, including temperature, moisture, and labile carbon pools. Collectively, these findings are consistent with the concept of nitrogen saturation under conventional fertilization rates. Optimizing these rates presents a significant opportunity to mitigate greenhouse gas emissions and air pollution while improving nitrogen use efficiency, thereby aligning agricultural production with climate goals and public health objectives without destabilizing short-term soil function.