Nitrification and Urease Inhibitors Reduce the Stimulated Nitrous Oxide Emissions by the Freeze-Thaw Cycles

Most studies have demonstrated that nitrification and urease inhibitors can reduce soil nitrous oxide (N2O) emissions from nitrogen-fertilized farmland. However, few studies have examined the potential impacts of these inhibitors on semi-arid agricultural farmland in the presence of freeze-thaw (FT) cycles. The purpose of this study was to assess the efficacy of applying the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) and the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) to soil nitrogen transformation and studying N2O emissions through simulated indoor FT incubation to offer theoretical and technological guidance for mitigating nitrogen loss in semi-arid farmland. The results showed that urea with DMPP under freeze-thaw conditions significantly increased the inorganic nitrogen content of the soil, kept the ammonium nitrogen content of the soil at a high level, suppressed the net nitrification rate of the soil, and reduced the cumulative emission of nitrous oxide (N2O) in the soil by nearly 87.6% compared to CK. Urea incubation with NBPT under freeze-thaw conditions also significantly reduced fluxes and cumulative N2O emissions. Due to the dual inhibition of soil nitrification rate by DMPP/NBPT and the FT cycle, the addition of DMPP/NBPT during soil FT could alleviate soil N2O emission caused by the effect of the FT cycle after urea addition and reduce soil nitrogen loss. The results indicate that the application of DMPP/NBPT can effectively alleviate the irrigated silt soil N2O emission during the FT period.