Sustained use of DMPP reduces its mitigation potential for N2O emissions: Field evidence and global implications

Nitrogen fertilization is a major driver of nitrous oxide (N2O) emissions, and nitrification inhibitors such as 3,4-dimethylpyrazole phosphate (DMPP) are widely used to mitigate them. However, the long-term effectiveness of DMPP remains uncertain. Here, in a three-year field trial in acidic tea plantation soils under fertilized conditions, we demonstrate that the N2O mitigation efficacy of DMPP progressively declines. This decline was mechanistically linked to treatment-induced microbial community adaptations: DMPP initially suppressed ammonia-oxidizing bacteria (AOB) but over time prompted a compensatory increase in ammonia-oxidizing archaea (AOA) and a compositional shift within the AOB community from Nitrosospira to Nitrosomonas. In our co-occurrence network analysis, the application of DMPP intensified niche competition and increased modularity, indicating enhanced microbial resilience. To contextualize these findings globally, we conducted a meta-analysis of 88 field studies, which confirmed that DMPP application reduced N2O emissions by an average of 49 %, but its effectiveness declined significantly with prolonged use. Using a random forest model trained on global datasets, we predicted a 12 % reduction in mitigation potential after five years of consecutive DMPP application. These results demonstrate that sustained DMPP application under nitrogen-fertilized regimes triggers ecological feedbacks that diminish its practical benefits. We therefore conclude that adaptive management strategies, such as rotating different nitrification inhibitors, are imperative to counter microbial adaptation and sustain mitigation efforts in the long term.