Low-temperature biochar for improving composting process via regulation of enzymatic stoichiometry and microbial community succession

This study investigated the effects of low-temperature and high-temperature biochar on carbon (C), nitrogen (N), and phosphorus (P) conversion and microbial succession during the co-composting of cow manure and corn stover. Enzymatic stoichiometry was examined to effectively estimate the changes in the process of composting. The addition of low-temperature biochar raised the composting temperature. Moreover, the humic acid content in the compost product increased by 10.77 % and 64.49 %, compared to the high-temperature biochar and the control, respectively. In addition, the germination index (GI) and total solids (TS) content in compost also increased by 11.21 %, 6.06 %, and 25.50 %, 5.01 %. Low-temperature biochar application significantly increased the activities of β-D-glucosidase (BG), β-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and alkaline phosphatase (AKP) activities. On the other hand, the potential C/P and N/P acquisition activities represented by lnBG/ lnAKP and ln (LAP + NAG)/lnAKP, respectively, decreased significantly. Owing to the unique physicochemical properties, low-temperature biochar altered the abundance of bacterial taxa, such as Proteobacteria, Firmicutes and Luteimonas, Stenotrophomonas, which play specific roles in the composting process. Redundancy analyses showed that low-temperature biochar added during the composting process regulated the microbial community succession, improved enzyme activity, and lifted the limitation of C, N, and P availability during microbial nutrient conversion, thereby improving the compost quality.