The study investigates the effects of biochar on soil organic carbon (SOC) mineralization and microbial carbon use efficiency (CUE) in a fine-textured agricultural soil. Using a 13C-glucose labeling technique, the researchers found that biochar addition reduced the mineralization of both native SOC and added glucose, indicating negative priming. Higher biochar application rates (30 Mg ha\(^{-1}\)) resulted in lower mineralization rates. Biochar also increased soil microbial biomass carbon (MBC) and CUE, suggesting enhanced microbial activity and efficiency in utilizing added glucose. The study further revealed that most of the added biochar particles were recovered in the free particulate organic matter (POM) fraction, and the retention of 13C in this fraction indicated that added 13C-glucose was preserved within the biochar particles. Additionally, biochar increased the formation of stable microbial residues (necromass) from added glucose, and the proportion of occluded POM, indicating reduced SOC mineralization. Overall, the findings demonstrate that biochar can enhance soil C sequestration by preserving SOC and increasing CUE, leading to the formation and stabilization of microbial necromass.The study investigates the effects of biochar on soil organic carbon (SOC) mineralization and microbial carbon use efficiency (CUE) in a fine-textured agricultural soil. Using a 13C-glucose labeling technique, the researchers found that biochar addition reduced the mineralization of both native SOC and added glucose, indicating negative priming. Higher biochar application rates (30 Mg ha\(^{-1}\)) resulted in lower mineralization rates. Biochar also increased soil microbial biomass carbon (MBC) and CUE, suggesting enhanced microbial activity and efficiency in utilizing added glucose. The study further revealed that most of the added biochar particles were recovered in the free particulate organic matter (POM) fraction, and the retention of 13C in this fraction indicated that added 13C-glucose was preserved within the biochar particles. Additionally, biochar increased the formation of stable microbial residues (necromass) from added glucose, and the proportion of occluded POM, indicating reduced SOC mineralization. Overall, the findings demonstrate that biochar can enhance soil C sequestration by preserving SOC and increasing CUE, leading to the formation and stabilization of microbial necromass.