Meta-Analysis of the Effect of Nitrification Inhibitors on the Abundance of N2o-Related Functional Genes in Agricultural Soils

Abstract

The application of nitrification inhibitors (NIs) in agricultural systems is an important strategy to enhance fertilizer nitrogen use efficiency and mitigate soil nitrous oxide (N2 O) emissions. Here, we conducted a global meta-analysis of 81 published studies to assess the response of N2 O-related functional gene abundances to NIs application. Application of NIs significantly reduced the abundance of ammonia-oxidizing bacteria (AOB), and nitrite reductase (nirS and nirK ) genes by 53.4%, 21.2% and 20.2%, respectively. Instead, NIs did not affect the abundances of ammonia-oxidizing archaea (AOA), nitrate reductase (narG ), and nitrous oxide reductase (nosZ ). The effectiveness of NIs on reducing the AOB abundance was influenced by N form, soil texture and sampling time after NI application. Specifically, NIs were more effective when a mixed inorganic and organic N source was applied, and with medium textured soils. The NIs effectiveness decreased with increasing sampling time. The response of AOB abundance to NIs application was not affected by the experimental condition (field vs. laboratory), NI type, N application rate, soil organic carbon (SOC) content and pH. The inhibitory effect of NI on nirS abundance decreased with increasing SOC. NIs decreased soil nitrifying enzyme activity (NEA) and denitrifying enzyme activity (DEA) by 26.5% and 29.3%, respectively, leading to an overall 64.8% reduction of N2 O emissions. Soil NEA correlated positively with the abundance of AOB but not with AOA. 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 N2 O emissions was attributed to the inhibiting effects on AOB, nirS and nirK genes. Our findings highlight that soil properties including SOC and texture, and management practices such as N input form are important factors that can be used to improve the efficacy of NIs in reducing N2 O emissions from agricultural systems.

Keywords: Meta-analysis, Denitrifier, Nitrifier, Microbial functional genes, Nitrification inhibitors