Potential of biochar integrated manganese sulfate for promoting pig manure compost humification and its biological mechanism.

This study aimed to clarify the effect of the integrated addition of different proportions of biochar (0 and 5%) and MnSO (0, 0.25%, and 0.50%) to pig manure compost. The results indicated the integrated use of biochar (BC) and Mn advanced the compost humification. In particular, the integrated use of 0.50% Mn and 5% BC showed higher total organic carbon degradation (20.67%) and humic acid production (81.26 g kg) than other treatments. Microbial community analysis showed the integrated use of BC and Mn regulated the diversity and community structure of organic matter-mineralizing microbes by maintaining the relative abundance of bacteria Firmicutes (54.62%) and Proteobacteria (38.05%) at high levels during the thermophilic period and boosting those of the fungi of Ascomycota (58.91%) and Actinobacteria (15.60%) during the maturity period of composting. This study illustrated the potential and biological mechanisms of integrating BC and Mn as additives in compost humification.