Liming promotes soil nitrite accumulation but reduces subsequent abiotic nitrous oxide emissions

Abstract Aims The mechanisms underlying nitrous oxide (N2O) production in limed soils with N fertilizer application are not well understood. This study aimed to investigate the effects of liming on nitrite (NO2-) accumulation and its contribution to subsequent N2O production in soils with varying concentrations of ammonium (NH4+) additions (50, 100, and 250 mg NH4+-N kg-1 soil). Methods Soil microcosm incubation was designed to investigate NO2- accumulation and N2O production in the acidic and limed vegetable soil after different levels of N inputs. Sterilization of samples was used to distinguish the biotic and abiotic N2O productions. DNA extraction and relative functional gene detection provided molecular evidence. Results Elevating soil pH to alkaline (pH 8.5) through liming caused a shift in the soil microbial community, with an increase in the abundance of ammonia oxidizing bacteria (AOB) and a decrease in nitrite oxidizing bacteria (NOB). This resulted in the conversion of half of the added NH4+ to NO2-, with higher NH4+ concentrations leading to more cumulative NO2-. However, the N2O production resulting from NO2- accumulation was relatively modest (max. 0.89 μg N kg-1 soil per hour). Further experiments demonstrated that 81.9-93.6% of N2O production associated with NO2- accumulation was driven by abiotic processes under aerobic conditions, while abiotic processes drove 42.4-54.8% of N2O production under anaerobic conditions. Additionally, liming reduced 92% of the abiotic N2O production compared to that observed in acidic soil. Conclusion Liming promotes soil nitrite accumulation but reduces subsequent abiotic nitrous oxide emissions.