DMPP Mitigated N2O and NO Production by Inhibiting Ammonia-Oxidizing Bacteria in an Intensified Vegetable Field under Different Temperature and Moisture Regimes

Vegetable soils with high nitrogen input are major sources of nitrous oxide (N2O) and nitric oxide (NO), and the incorporation of nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) into soil has been documented to effectively reduce emissions. However, the efficiency of DMPP in terms of soil N2O and NO mitigation varies greatly depending on soil temperature and moisture levels. Thus, further evaluations of DMPP efficiency in diverse environments are required to encourage widespread application. A laboratory study was established to investigate the interactive effects of DMPP, soil temperature (15, 25 and 35 °C) and moisture (55% and 80% of water holding capacity (WHC)) on the nitrification rate, N2O and NO production, and the abundance of nitrifiers and denitrifiers. The results indicated that incubating soil with 1% DMPP led to a partial inhibition of the nitrification rate and N2O and NO production, and the percentage reduction of N2O was higher than that of NO (69.3% vs. 38.2%) regardless of incubation conditions. Increased temperatures promoted the nitrification rate but decreased soil N2O and NO production. Soil moisture influenced NO production more than N2O production, decreasing with increased water content. The inhibiting effect of DMPP on cumulative N2O and NO production decreased with temperature at 55% WHC. Conversely, the inhibiting effect of DMPP on cumulative N2O production increased with temperature at 80% WHC. Based on the correlation analyses and automatic linear modeling, net N2O and NO mitigation were attributed to the decrease in AOB-amoA gene abundance and NO2--N concentration. Overall, our study showed that DMPP suppressed both N2O and NO production by regulating the associated AOB-amoA gene abundance and NO2--N concentration. These findings improve our insights regarding the implications of DMPP for N2O and NO mitigation in vegetable soils under various climate scenarios.