Biochar improves soil organic carbon sequestration potential in the topsoil and subsoil of a paddy field

We investigated the carbon sequestration potential and underlying mechanisms of a paddy soil amended with biochar for 4 years. By adding maize straw and incubating the soil for 60 days in the laboratory at depths of 0–15 cm, 15–30 cm, and 30–50 cm, we found that biochar reduced soil organic carbon mineralization by 13.5 %, 27.8 % and 16.5 %, respectively. It also decreased cumulative net carbon mineralization and metabolic quotient values induced by fresh substrates at all depths. In addition, biochar and straw increased topsoil hydrolase activity and enhanced the competitiveness of fungi and gram-positive bacteria in the subsoil.