Nitrous Oxide Emissions In Response To Long-Term Application Of The Nitrification Inhibitor Dmpp In An Acidic Luvisol

One of the options recommended by the Intergovernmental Panel on Climate Change (IPCC) to reduce N2O emissions from agricultural soils is the application of nitrification inhibitors (NIs). However, the effects of longterm in situ application of 3,4-dimethylpyrazole phosphate (DMPP), one of the important NIs, on N2O emissions from agricultural soils are not well documented. In this study, a field trial was conducted to determine N2O emissions in response to DMPP application for six consecutive years (2010-2015) on a rainfed acidic luvisol planted with maize in Northeast China, as well as the effects on the soil microbial communities after six years. Three treatments were used, i.e., no urea (CK), urea (SU), and urea plus DMPP (DMPP). The results showed large intra- and interannual variations in the N2O fluxes for all treatments. The N2O mitigation efficiency of DMPP varied from 18.4 to 50.3% across the six cycles, which was mainly attributed to the amount of precipitation and its annual distribution. The annual N2O emissions and N2O emissions factor during the six years were significantly mitigated by DMPP applications, with mean reductions of 29.9 and 47.9%, respectively. The abundances of bacterial 16S rRNA genes, ammonia oxidizer genes, and denitrifier functional genes in the soils collected 10 days after fertilization in May 2015 and again in September were determined. In May 2015, DMPP application significantly decreased the ammonia-oxidizing bacteria (AOB) amoA gene copy number by 77.7% and increased the nosZ gene copy number by 116.8%. However, in September 2015, even after the six-year application period assessed in May, there was no significant effect on gene abundance due to DMPP. Overall, the repeated annual application of DMPP in the spring effectively reduced N2O emissions from acidic luvisol soil, yielding no significant long-term shifts in soil bacterial communities.