Metagenomic insights into nitrification and urease inhibitors promote glyphosate degradations and reduce soil nitrous oxide emissions

Organic herbicide pollution and greenhouse gas emission are major concerns in achieving sustainable agriculture and forestry.Nitrification and urease inhibitors have been used to improve fertilizer nitrogen(N)use efficiency,but their interactions with herbicides have rarely been studied.A comprehensive understanding of the impacts of N-cycling inhibitors on pesticide degradation and nitrous oxide(N2O)emission could help minimize the environmental risks of herbicide pollution and global climate change.In this study,we investigated glyphosate residues and N2O emission in camellia plantation soils,as influenced by nitrification inhibitors 3,4-dimethyl pyrazole phosphate(DMPP)and dicyandiamide(DCD)and urease inhibitor thiophosphoric triamide(NBPT),under 60%and 90%water holding capacity(WHC).The soil properties,glyphosate residues,N2O emissions,microbial communities and their comprehensive linkages were also analyzed.Compared with the control treatment,applying DMPP,DCD and NBPT significantly decreased glyphosate residues by 32.9%,60.3%and 35.6%under 90%WHC,respectively.Soil glyphosate residues were negatively correlated to the abundances of Acidobacteria and phnX gene.Contributions of soil moisture to glyphosate degradation were correlated to increases in phnJ,sox A and sox D genes.Relative to the control treatment,NBPT applications decreased cumulative N2O emissions by 56.6%and 91.4%under 60%and 90%WHC,respectively.Soil N2O emissions were regulated by soil water contents partly through affecting changes in soil DOC,DON,NH4+-N and NO3--N contents as well as abundances of functional nos Z,nar G,norB and norH genes.The promotion of glyphosate degradation and suppression of soil N2O emission by the N-cycling inhibitors suggested that applying N-cycling inhibitors might be an effect strategy to simultaneously reduce environmental pollution of pesticides and global climate change.