A Study of the Effect of Biochar Additive on the Manure–Compost–Soil Process and Its Bacterial Succession

The manure–compost–soil process is the main avenue for using agricultural livestock waste. Biochar not only impacts the composting process but also enhances the soil’s organic matter and nitrogen content when applied with compost. This paper explores the profound impact of biochar as an additive on the manure–compost–soil process, uncovering novel mechanisms driving enhanced soil health and bacterial succession. The basic physicochemical properties (organic matter, total nitrogen, etc.) and microbial structure of the composting and soil samples were analyzed. Biochar additive increased the C/N ratio and the total carbon content of the compost. Biochar, compost, and biochar-based compost improved the total carbon and organic matter of the soil. After high-temperature composting, Saccharomonospora (from 2.68% to 0.80%), Atopostipes (from 5.71% to 0.13%), and Lactobacillus (from 5.27% to 0.04%) were almost eliminated. Lysobacter, Glutamicibacter, and Streptomyces were the dominant genera in the soil samples, promoting plant growth. Nocardiopsis, Saccharomonospora, Bacillus, and Oceanobacillus dominated the genera in the whole manure–compost–soil process. Thus, composting could eliminate the toxic or negative bacteria directly deposited into soil by manure. Those genera arising from compost or biochar-based compost in the soil could contribute to organic matter’s cycle.