Objective This study aims to clarify the effects of different fertilization regimes on the carbon sequestration potential of dryland black soil and the microbial community structure and function under exogenous carbon addition. The findings are of great significance for improving soil fertility and fertilization management in agricultural black soils.

Methods A 36-year field experiment was conducted at the Black Soil Ecological Environment Key Field Science Observation Station, involving different fertilization treatments, including no fertilization (CK), chemical fertilization (NPK), and organic fertilization (OM). Exogenous carbon was added to simulate carbon sequestration, and high-throughput sequencing was used to analyze the microbial community structure and functional response to exogenous carbon addition under long-term fertilization regimes.

Results Glucose addition significantly increased soil organic carbon content across all fertilization treatments, with the highest carbon sequestration potential observed in OM soil (16.7%), followed by CK (13.9%) and NPK (9.5%). The trend in microbial abundance was consistent with SOC accumulation, with the magnitude of increase following the order CK < NPK < OM. High-throughput sequencing further revealed pronounced differences in microbial responses among fertilization treatments. At the phylum level, the Proteobacteria phylum showed the most significant response to carbon addition, with increases of up to 35.8%, 26.5%, and 27.2% in CK, NPK, and OM soils, respectively. At the genus level, the Luteimonas genus exhibited the most significant response to carbon addition, with increases of 0.10%, 2.90%, and 9.50% in CK, NPK, and OM soils, respectively. Under exogenous carbon addition, the soil microbial functions under different long-term fertilization patterns also showed significant differences. Among them, the dominant aerobic respiration heterotrophic function in OM soil showed a significantly higher increase than in CK and NPK soils. The random forest model further analysis indicated that the key microbial groups and microbial functions of the soil were important factors causing the differences in the carbon sequestration potential of different fertilization treatments, with a cumulative contribution rate of up to 69.6% to 78.9%.

Conclusion Long-term application of organic fertilizers exhibited the strong carbon sequestration capacity, achieved by altering the soil microbial community and enhancing microbial abundance and carbon sequestration functions. Therefore, rational application of organic fertilizers is of great significance for improving the fertility of black soil in farmlands.