LAUSR

The aim of this study was to identify the effects of ammonia-oxidizing bacteria (AOB) inoculation on humus formation. Both nitrogen conversion and humus formation were considered as the main processes, because NH4+-N-like compounds not only substrates of nitrification, but also precursors of humus. During composting, the inoculation of AOB indeed increased humus concentration by fixing NH3 emission as NH4+-N, but it has also promoted nitrogen transformation. While the main reason was the changed bacteria community structure caused by inoculating AOB. Moreover, the relationship between bacteria and nitrogen transformation and humus formation has become closer. And bacteria were more likely to synthesize humus. Therefore, it is conjectured that AOB inoculation could not only provide NH4+-N for humus formation, but also enhance the anabolism of microorganisms. This suppose has been confirmed by structural equation model in this study. Therefore, AOB inoculation has a driving effect on promoting humus formation.