Effects of microbial agents on nitrogen conversion and bacterial succession during pig manure composting

Aerobic composting can recycle nutrients from animal manure. Adding microorganism inoculants is an effective way to accelerate composting process. The study aimed to evaluate effects of inoculating with microbial agents on nitrogen conversion and bacterial community succession in pig manure composting. 3 composting treatments were conducted including no microbial inoculant (CK), inoculating thermophilic degrading bacteria (T1), and compound commercial microbial agents (T2). The results showed that T1 advanced the time for entering the thermophilic stage (>50 ℃), and accelerated organic matter degradation. T1 produced more NH3 than other treatments. TN in group T1 and T2 was significantly greater than CK in composting maturity stage (after 14–15 d, T ≤ 40 ℃). (Final C/N)/(Initial C/N) of group T1 and T2 was 0.66, 0.65, and GI was 90.7 and 87.6, respectively. T1 improved the relative abundance of Actinobacteria, Firmicutes, Proteobacteria at the phylum level and increased Bacillus genera at genus level during the composting process. In conclusion, we demonstrated that pig manure composting added to thermophilic degrading bacteria effectively improved the quality of compost.