Enhanced Rock Weathering Promotes Soil Organic Carbon Accumulation: A Global Meta-Analysis Based on Experimental Evidence.

Enhanced rock weathering (ERW) has emerged as a promising carbon dioxide removal (CDR) strategy with the potential to modulate soil carbon sequestration, yet empirical assessments of its impacts remain limited. Here, we address this knowledge gap through a global meta-analysis synthesizing 74 publications. Synthesized results from field experiments showed that crushed rock amendment increased soil organic carbon (SOC), mineral-associated organic carbon, and particulate organic carbon by an average of up to 3.8%, 6.1%, and 7.5%, respectively, with no significant impact on dissolved organic carbon and soil inorganic carbon. SOC accrual was driven by elevated soil exchangeable Ca, increased microbial biomass, and improved soil structure, with local climate regulating these responses. Machine learning simulations of global croplands revealed pronounced site dependency in ERW impacts on SOC, which was positive in low-latitude (warm and humid) regions (40° N-30° S) but negative in high-latitude (cold and dry) regions. Additionally, the effects of ERW on SOC are dose- and duration-dependent. Our simulations indicated that application amounts of 50-500 g m-2 are optimal for maximizing SOC sequestration, with positive effects diminishing and negative impacts intensifying beyond this range. This empirical synthesis confirms the efficacy of ERW-particularly when Ca-rich silicate rocks in-promoting SOC sequestration and long-term CO2 sequestration. Maximizing the CDR potential of ERW requires integrating site-specific climatic and edaphic characteristics with optimized application amounts and duration. Our findings provide insights critical for balancing the costs and benefits of rock weathering for CDR and highlight the importance of ERW as a sustainable strategy for soil carbon management and climate change mitigation.