Paenibacillus polymyxa biofertilizer application in a tea plantation reduces soil N2O by changing denitrifier communities

Increasing the use of nitrogen fertilizers in tea orchards has led to intense nitrous oxide (N2O) emissions. Foliar application of Paenibacillus polymyxa biofertilizer has been proven to be beneficial for organic tea production. In this study, tea yield and quality were significantly improved after application of P. polymyxa biofertilizer compared with the control but were not significantly different from chemical fertilizer treatments. However, the average N2O fluxes in tea fields treated with chemical fertilizers and biofertilizers (225 kg N·ha−1·year−1 for both) were 50.6–973.7 and 0.6–29.1 times higher than those in the control treatment, respectively. Pot experiments conducted to explore the mechanism of N2O reduction induced by P. polymyxa biofertilizer showed that applying P. polymyxa in addition to urea could reduce N2O fluxes by 36.5%–73.1%. Quantitative PCR analysis suggested that a significant increase in the quantity of nirK and nosZ genes was linked to the reduction of N2O, and high-throughput sequencing of nosZ revealed active and potentially efficient denitrifiers in different treatments. Our findings suggest that P. polymyxa biofertilizer is in line with the requirements of modern agriculture, which aims to increase product yield and quality while reducing negative environmental impacts.