Soil N2O production and the δ15N–N2O value: Their relationship with nitrifying/denitrifying bacteria and archaea during a growing season of soybean in northeast China

•Soil N2O fluxes and production processes were mainly affected by soil WFPS.•Soil AOB amoA abundance was significantly correlated with δ15N values of emitted N2O.•AOB rather than AOA played a more important role in nitrification of the tested soil.

Nitrous oxide, one of the principal greenhouse gases that can cause global warming, is mainly produced in soil via a series of microbial enzymatic processes. However, source identification of N2O in soil has been a great challenge. In this study, a laboratory incubation experiment was conducted with soils sampled from a soybean field on six sampling dates to evaluate a new approach for identifying soil N2O production processes. The isotopic signatures of soil-emitted N2O, the copy numbers of nitrification- and denitrification-related genes, and some soil properties were monitored simultaneously. Results showed that the soil N2O flux was related to water-filled pore space (WFPS) during the sampling period (r = 0.73, p < 0.01). The δ15N values of soil-emitted N2O on the six sampling dates ranged from −11.3‰ to +1.6‰, and significant differences among these values were found. The δ15N–N2O values were significantly correlated with the copy numbers of AOB amoA (r = 0.80, p < 0.01) but not with those of AOA amoA. These results suggested that soil WFPS was a determinative factor of N2O production processes, and AOB played a more important role in N2O production in the tested soil. Therefore, the combination of a stable isotopic signature with abundance of the soil microbial community should be a more effective approach to identify soil microbial processes of N2O production.