Oxygen Availability Governs the Mitigating Effect of 3,4-Dimethylpyrazole Phosphate on Nitrous Oxide Emissions from Paddy Soils under Various Water Managements

Alternate wetting and drying (AWD) frequently triggers nitrous oxide (N2O) emissions from paddy fields, while the inhibitory effect of 3,4-dimethylpyrazole phosphate (DMPP) on N2O under various water managements remains uncertain. Here, we evaluated the effects of DMPP on N2O emissions and associated biological indicators under three water managements: continuous flooding (CF), mild AWD (Mi-AWD), and moderate AWD (Mo-AWD). The Mi-AWD and Mo-AWD practices increased N2O emissions by 2- and 0.9-fold compared to the CF treatment, respectively, due to enhanced oxygen availability, facilitating coupled nitrification-denitrification. DMPP application notably reduced N2O emissions in the AWD treatments, attributed to the reductions in nitrifier abundances, nitrification rates, and nitrate accumulation. Nevertheless, DMPP failed to suppress nitrification and, thereby, N2O emissions in the CF treatment. Overall, DMPP effectively mitigates N2O emissions under oxygen-rich AWD rather than anaerobic CF conditions, highlighting that the trade-offs between water-saving irrigation and N2O mitigation can be overcome via nitrification inhibitors application.