Effect of three rhizobacteria on lettuce growth and soil N2O emission and their impact on the rhizosphere bacterial community in acidic field experiments

Abstract Aims Acidic soils have a high potential for nitrous oxide (N2O) emission. Plant growth-promoting rhizobacteria (PGPR) may mitigate N2O emissions in acidic soils; however, the reduction capacity and their microbiological mechanisms are poorly understood. We investigated the effects of three PGPR strains (Bacillus subtilis subsp. subtilis NRCB002, Stutzerimonas stutzeri NRCB010, and B. velezensis NRCB026) on crop growth and N2O emissions in acidic soils, and explored their microbial mechanisms. Methods and results A field experiment was conducted to assess the effects of inoculation with NRCB002, NRCB010, and NRCB026 on lettuce growth and N2O emissions from acidic soil and to study the associated microbiological mechanisms. The results indicated that inoculation with NRCB002, NRCB010, and NRCB026 significantly promoted lettuce growth and decreased N2O emissions from soil by 16.3%, 36.2%, and 45.8%, respectively. Furthermore, inoculation with these three strains altered the microbial community composition and nitrogen cycle functional gene abundance in acidic soils. Structural equation models indicated that inoculation with these three strains affected N2O emissions from the soil by modulating soil pH, relative abundance of Proteobacteria, and nosZ gene copy numbers. N2O emissions from soil inoculated with NRCB002 were negatively correlated with nosZI gene copy number, while NRCB010 and NRCB026 were negatively correlated with nosZII gene copy number. Conclusions PGPR strains enhanced lettuce growth and decreased acidic soil N2O emissions under field conditions. Among the three strains, NRCB026 significantly decreased N2O emission from acidic soil.