Geoderma (Apr 2025)
Nitrification inhibitors reduce N2O emissions from Mollisols by potentially targeting Nitrosospira cluster 3a and denitrifiers
Abstract
Nitrification inhibitors (NIs) are widely used to mitigate nitrous oxide (N2O) emissions from agricultural soils. However, its efficiency is highly uncertain owing to varying environmental conditions and still-debated inhibition mechanisms, especially the responses of the nitrifiers and denitrifiers responsible for N2O production. Here, we conducted microcosm incubations to investigate the comparative effectiveness of three NIs (DCD, DMPP, and nitrapyrin) on N2O emissions from cultivated Mollisols under contrasting moisture levels (60 % and 90 % water-filled pore space, WFPS). The soil nitrification rate, N2O-related gene abundance, and community composition of ammonia-oxidizing bacteria (AOB) were determined. The results showed that all NIs effectively inhibited nitrification, with DCD and DMPP having higher efficacy than nitrapyrin, regardless of soil moisture conditions. Interestingly, a greater decrease in N2O emissions was observed under 90 % WFPS than 60 % WFPS (39.0–47.6 % vs. 26.8–31.9 %). NIs selectively decreased the amoA gene abundance in AOB rather than in ammonia-oxidizing archaea. The most abundant AOB (> 90 %) belonged to Nitrosospira. RDA analysis revealed that the AOB Nitrosospira cluster 3a had the greatest relationship with N2O emissions, and its abundance was significantly decreased with NI amendments. Moreover, non-target denitrifying genes (nirS and nirK) were suppressed, particularly at high moisture levels, which further contributed to reduced N2O emissions. Overall, our findings highlight the significant role of environmental conditions, keystone species of AOB, and non-targeted effects on denitrifiers on the efficacy of NIs. Additionally, these results imply that NIs are a potent option for fertilizer management to mitigate N2O emissions and that DCD and DMPP have promising prospects for the cultivated Mollisols agro-system under climate change with intensifying extreme rainfall events.
