Meta-analysis of the effect of nitrification inhibitors on the abundance and community structure of N2O-related functional genes in agricultural soils

Application of nitrification inhibitors (NIs) in agricultural systems is an important strategy to enhance fertilizer nitrogen use efficiency and mitigate soil nitrous oxide (N2O) emissions. Here, we conducted a global meta-analysis of 88 published studies to assess the response of N2O-related functional gene and transcript abundances, and community structure to NIs application. Application of NIs significantly reduced the abundance of ammonia-oxidizing bacteria ammonia monooxygenase (AOB amoA) genes, AOB amoA transcript and nitrite reductase (nirS and nirK) genes. The effectiveness of NIs on reducing the AOB amoA abundance was influenced by N form, soil texture, soil pH and the experimental type (field vs. laboratory). Specifically, NIs were more effective when a mixed inorganic and organic N source was applied to a medium-textured soils. The NIs effectiveness increased with increasing soil pH. The response of AOB amoA abundance to NIs application was not affected by NI type, N rate, soil moisture, soil temperature and soil organic carbon (SOC). The inhibitory effect of NIs on nirS abundance increased with increasing soil temperature. NIs decreased soil nitrifying enzyme activity (NEA) and denitrifying enzyme activity (DEA) by 34.5 % and 27.0%, respectively, leading to an overall 63.6 % reduction of N2O emissions. Soil NEA correlated positively with the abundance and community structure of AOB amoA but not with AOA amoA. Decrease in DEA with NIs application coincided with the decreasing nirS and nirK abundances. This global-scale assessment demonstrates that the effectiveness of NIs in reducing N2O emissions was attributed to the inhibiting effects on AOB amoA, nirS and nirK genes. Our findings highlight that NIs' inhibition effects on bacterial ammonia-oxidizing community and the encode enzymes in transformation of nitrite to nitric oxide are the main mechanisms for mitigation of N fertilizer-induced N2O emissions.

Automated summary

The application of nitrification inhibitors (NIs) in agricultural systems plays a crucial role in improving fertilizer nitrogen use efficiency and reducing soil nitrous oxide (N2O) emissions. A global meta-analysis of 88 published studies revealed that NIs significantly decreased the abundance of ammonia-oxidizing bacteria ammonia monooxygenase (AOB amoA) genes, AOB amoA transcript, and nitrite reductase (nirS and nirK) genes. The effectiveness of NIs in reducing AOB amoA abundance was influenced by factors such as N form, soil texture, soil pH, and experimental type. Overall, NIs led to a considerable reduction in N2O emissions through inhibiting AOB amoA, nirS, and nirK genes.