Effects of the Fertilizer Added with DMPP on Soil Nitrous Oxide Emissions and Microbial Functional Diversity

Agricultural sites contribute extensively to emissions in atmosphere of climate-altering gases such as nitrous oxide. Several strategies have been considered to mitigate the impact of agriculture on climate, among these the utilization of fertilizers added with nitrification inhibitors, such as the DMPP (3,4-dimethylpyrazole phosphate), may represent a suitable solution. DMPP inhibits the growth and activity of ammonia-oxidizing microorganisms, in particular the ammonia-oxidizing bacteria, which are involved in N2O production. At present, little information is available on the effects of DMPP on the catabolic diversity of soil microbial community. In this study, the N2O emission by soil has been performed by using the static chamber technique. The biological determinations of the microbial biomass carbon and the catabolic profile have been assessed by measuring the substrate-induced respiration during the entire growing season of a potato crop under two nitrogen treatments: fertilization with or without DMPP. Our results did not show a clear mitigating N2O emission by DMPP, even if a tendency to lower N2O fluxes in DMPP plots occurred when soil temperatures were lower than 20 °C. Conversely, DMPP deeply affected the microbial biomass and the catabolism of soil microorganisms, exerting a negative effect when it is accumulated in excessive doses in the soil, limiting the growth and the capacity of soil microorganism communities to use different substrates.