Effects of nitrification and urease inhibitors on ammonia-oxidizing microorganisms, denitrifying bacteria, and greenhouse gas emissions in greenhouse vegetable fields

Soil microorganisms and N cycling are important components of biogeochemical cycling processes. In addition, the study of the effects of nitrification and urease inhibitors on N and microorganisms in greenhouse vegetable fields is essential to reducing N loss and greenhouse gas emissions. The effects of nitrification inhibitors [2-chloro-6-(trichloromethyl) pyridine (CP), dicyandiamide (DCD)], and urease inhibitor [N-(n-butyl) thiophosphoric triamide (NBPT)] on soil inorganic N (NH4+-N, NO2−-N and NO3−-N) concentrations and the production rates of greenhouse gases (N2O, CH4, and CO2) in greenhouse vegetable fields were investigated via indoor incubation experiments. Polymerase chain reaction amplification and high-throughput sequencing technology (Illumina Miseq) were used to explore the community structure and abundance changes of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and denitrifying bacteria (nirK and nirS). The results showed that CP and DCD obviously inhibited NH4+-N conversion, and NO2−-N, and NO3−-N accumulation, NBPT slowed down urea hydrolysis and NH4+-N production, and the apparent nitrification rates of soil were in the following order: NBPT > DCD > DCD + NBPT > CP + NBPT > CP. Compared with urea treatment, the peak N2O production rate of inhibitor treatment decreased by 73.30–99.30%, and the production rate of CH4 and CO2 decreased by more than 66.16%. DCD and CP reduced the abundance of AOA and AOB, respectively. Furthermore, NBPT hindered the growth of ammonia-oxidizing microorganisms and nirS-type denitrifying bacteria, and urea and nitrification inhibitors were detrimental to the growth of Ensifer and Sinorhizobium in the nirK community. Nitrification and urease inhibitors can effectively slow down nitrification and greenhouse gas emissions, reduce N loss and improve soil quality by inhibiting the growth of ammonia-oxidizing microorganisms and denitrifying bacteria.