Sustainable Land Management Practices Enhance Soil Microbial Biomass Carbon in Global Croplands.

Soil microbial biomass carbon (SMBC) is an essential indicator of microbial activity and soil health, reflecting ecosystem functioning and sustainability. We synthesized data from 221 peer-reviewed studies from 1988 to 2024 to evaluate the global effects of six sustainable land management (SLM) practices-organic amendment, inorganic fertilization, integrated fertilization, conservation tillage, crop diversification, and crop residue management-on SMBC in global croplands. Except for inorganic fertilization, which had a slight negative effect, all practices were associated with higher SMBC concentration values, with treatment plots exhibiting, on average, 23.5% higher SMBC concentration than control plots across the compiled global database. The degree of these effects varied on the basis of environmental factors, especially aridity and soil texture. Based on the compiled dataset and extrapolation approach, SLM practices were associated with an estimated 27% increase in global SMBC stocks, corresponding to approximately 322 million tonnes of microbial carbon across global croplands although this estimate should be interpreted with caution due to spatial heterogeneity in data coverage and uncertainties associated with generalized assumptions in bulk density and soil depth. Integrated fertilization and crop diversification were particularly effective across all aridity classes. Subgroup analyses confirmed that soil texture, aridity, and management practices each significantly affected SMBC. However, we observed notable combined effects on SMBC only when two environmental factors changed at the same time. This suggests that although SLM practices may help to reduce the harms of single stressors, the combined effects of multiple stressors can greatly change microbial carbon dynamics. These findings highlight the importance of developing context-specific SLM strategies to enhance microbial carbon pools and improve soil health, thereby providing guidance for land managers, policymakers, and farmers to promote more resilient and sustainable agricultural systems worldwide.