Edaphic Factors and Fertilization Practices Jointly Regulate Microbial Necromass Contribution to Soil Organic Carbon in Global Croplands

Effectively managing soil organic carbon (SOC) for soil quality and climate mitigation requires a mechanistic understanding of its stabilization pathways. Microbial necromass carbon (MNC), a major source of persistent SOC, is influenced by climate, soil properties, and agricultural management. However, how these factors jointly shape the contribution of MNC to SOC (MNC/SOC) at a global scale remains largely unknown. Here, we synthesized a global dataset comprising 636 observations from 60 peer‐reviewed articles on cropland topsoils to identify the dominant drivers of MNC/SOC and provide actionable insights for its management. The average MNC/SOC in global croplands was 0.47 ± 0.19. Our analysis indicated that soil clay content and the C/N ratio were the primary regulators of MNC/SOC; specifically, clay content showed a positive correlation, while the C/N ratio exhibited a negative correlation. Furthermore, we found that fertilizer type, rather than application rate, emerged as the key lever controlling the MNC/SOC. Compared to mineral fertilization, organic fertilization significantly increased 27% of MNC/SOC, mainly resulting from the amplified positive effect of clay and reduced negative impact of soil C/N ratio. Global modeling further indicated that organic fertilization was the superior strategy for enhancing MNC/SOC across the majority of global croplands, particularly in clay‐rich regions, whereas mineral fertilizers may be more effective in a few arid regions. Collectively, these findings demonstrate that prioritizing organic fertilization can effectively leverage positive clay interactions and mitigate C/N stoichiometric constraints, offering a globally effective strategy to strengthen the microbial pathway of soil carbon stabilization and combat land degradation.