Effects of the nitrification inhibitor dicyandiamide (DCD) on N2Oemissions and the abundance of nitrifiers and denitrifiers in two contrasting agricultural soils

Abstract

Nitrous oxide (N2O) is a trace gas and is mainly produced through the microbial-mediated nitrification and denitrification processes in agricultural soils. Dicyandiamide (DCD) is a powerful nitrification inhibitor (NI) which can mitigate N2O production from soil. However, it remains poorly understood how N2O emission and associated microbes are affected by DCD application across different agricultural soils. Here, we carried out a 21-day laboratory microcosm incubation experiment to examine the impact of ammonium sulfate and DCD applications on N2O production and the abundance of nitrifiers and denitrifiers in two contrasting agricultural soils. The abundance of the functional genes was quantified by quantitative PCR to investigate the population changes in response to ammonium sulfate and DCD addition. Higher N2O production emitted followed the application of ammonium sulfate (287.9 ng N2O–N g−1 soil) in the alluvial soil was obtained compared to that (84.9 ng N2O–N g−1 soil) in the red soil. The average N2O emission rate in the NH4 + treatment from the alluvial soil was significantly higher than that from the red soil, and DCD addition remarkably reduced N2O emission rates in both soils during the 21-day incubation. We also observed that the abundance of ammonia-oxidizing bacteria (AOB) amoA gene and the nirK gene was positively correlated with total N2O emissions in the alluvial soil, but only AOB amoA gene abundance was significantly related to the total N2O emissions in the red soil. These results suggested that DCD was more effective in inhibiting N2O production in the alluvial soil than in the red soil. DCD could effectively reduce N2O emission by suppressing the growth of microorganisms containing AOB amoA gene and the nirK gene in the alluvial soil.