Linking changes in soil microbial community with nitrous oxide gas emissions

VEA MURGIA, DANIELA; FIGUEROLA, EVA; FRASIER, ILEANA; GRASSO, DANIEL; VARGAS GIL, SILVINA

Quilmes

Congreso; 3er. Congreso Latinoamericano de Ecología Microbiana, ISME-Lat 2023; 2023

Internationa Society of Microbial Ecology

Understanding the role ofbacterial diversity in the mechanisms of biological regulation involved inthenitrogen (N) cycle is mandatory in order to comprehend the impact of soilmanagementstrategies promoted to mitigate greenhouse gas (GEI) emissions inagricultural soils. Theobjective of this study was to assess the response ofthe soil microbial community to changes innitrous oxide (N2O) emission ratesunder different soil management practices. The study wascarried out on a farmlocated at Anguil, La Pampa (S 36° 36 ́ 37.95 ́ ́; W 63° 58 ́ 48.22 ́ ́), inthesemiarid pampa region of Argentina. The treatments were soybean with rye ascover crop(CS), and soybean without cover crop (SS) belonged to a long-termtrial established in 2009 in astrip design (50 x 10 m) with 4 replicates underno-till. The third treatment was a naturalgrassland (R) used as a referencecondition. Soil samples at 0-0.01 m depth corresponding topreviouslyidentified N2O emission peaks measured during 2019 to 2021 were selected.Thus,three moments were defined: before, during the N2O peak, and after it. DNA wasextractedfrom those soil samples, and the V4 region of 16S rDNA was sequencedusing Illumina. Bacterialcommunity structures were analyzed through NMDS,revealing treatment-based sampleclustering. The presence and abundance ofenzymes involved in the N metabolism were inferredwith PICRUST. Mixed linearmodels were used to find differences in enzyme abundances. Theresults showedthat soil bacteria communities were similar before and during the N2O peakforthe R treatment, and also differed from the communities after the N2O peak. Forboth CS andSS treatments, bacterial communities’ before-peak were differentfrom those observed duringand after-peak. Also, NO reductase increases at the time of the N2O emission peak. Correlationsamong soil physicochemicalvariables and denitrification enzymes indicated positive correlationswith thepercentage of water-filled pore space and root-C/N ratio, while negativecorrelations weredetected with root-C, soil microbial biomass, residues, andsoluble C, as well as with root-N.These results provide a detailed insightinto the role of bacterial diversity and biological regulationon N2O emissionsin agricultural soils.