Wollastonite addition stimulates soil organic carbon mineralization: Evidences from 12 land-use types in subtropical China

Enhanced rock weathering through adding silicate rock powder to soil has been increasingly considered as an effective means of removing CO₂ from the atmosphere. However, the potential impact of silicate rock powder addition on the stability of soil organic carbon remains largely unknown, which adds an uncertainty to its effectiveness in mitigating atmospheric CO₂. In this study, the response of soil CO₂ efflux to wollastonite addition was evaluated for 12 land-use types in a subtropical region of China through an incubation experiment. Results showed that wollastonite addition significantly (P < 0.05) increased soil CO₂ efflux over the control by an average of 330.97 ± 29.25% during the incubation period. Approximately 90% of the variance in soil CO₂ efflux was explained by soil properties in this study. Increased soil pH, dissolved organic carbon and available silicon induced by wollastonite addition were the main reasons responsible for the increase in soil CO₂ emission. Soils having lower pH values responded to wollastonite addition with a higher increase in CO₂ emissions. Based on numerous land-use types, our study showed that wollastonite application will cause substantial increase in the mineralization of soil organic carbon in acidic soil, which may weaken the effectiveness of enhanced rock weathering strategies as a tool for CO₂ sequestration.