Efficiency and mechanism of reducing ammonia volatilization in alkaline farmland soil using Bacillus amyloliquefaciens biofertilizer

Ammonia volatilization from the farmland caused by the application of synthetic nitrogen fertilizer is the most important source of anthropogenic ammonia emissions. Biofertilizer application has been considered as an alternative option for agriculture sustainability and soil improvement. In this study, field trials were carried out to investigate the efficiency of Bacillus amyloliquefaciens (BA) biofertilizer on alleviating ammonia volatilization in alkaline farmland soil and increasing crop yield and nitrogen utilization. Potential response mechanisms were investigated from soil enzyme, nitrogen cycle function genes and microbial community levels. Compared with conventional fertilization, BA biofertilizer application reduced the ammonia volatilization by 68%, increased the crop yield and nitrogen recovery by 19% and 19%, respectively. Soil enzyme activity analysis showed that BA biofertilizer inhibited the urease activity and enhanced the potential ammonia oxidation (PAO). In addition, BA biofertilizer application also increased the bacterial amoA gene abundance, while decreased the ureC gene abundance. BA biofertilizer also significantly altered the community structure and composition, and especially raised the abundance of ammonia oxidation bacteria (AOB), while no changes were observed in abundance of nitrite oxidation bacteria (NOB). Briefly, BA biofertilizer was approved to reduce the transformation of fertilizer nitrogen to NH4+-N, simultaneously accelerating NH4+-N into the nitrification process, thus decreasing the NH4+-N content remained in alkaline soil and consequently alleviating the ammonia volatilization. Thus, these results suggested that the application of BA biofertilizer is a feasible strategy to improve crop yields and reduce agricultural ammonia emissions.