Impact of farming practices on soil microbial biomass: An international synthesis

International audience

English. Agricultural intensification during the 20th century has profoundly altered soil ecosystems, underscoring the urgent need for sustainable practices enhancing soil quality. Soil microbial biomass is a key indicator of soil quality, reflecting both biological and ecosystem resilience. However, existing studies often focus on specific practices or regions, limiting their applicability to diverse farming systems. This study synthesizes data from 280 scientific publications selected through the Web of Science database, covering a wide geographical range, to evaluate the effects of the main agronomic levers, i.e. tillage, fertilization, crop rotation diversity including inter-cropping, and pesticide use on soil microbial biomass. Statistical analyses revealed that soil microbial biomass is generally promoted by organic fertilization (+64 % to +76 %), reduced tillage (+32 % to +41 %) and increased crop diversity (+10 % to +47 %), while mineral fertilization shows more modest effects (+7 % to +35 %). These results comply with the “carrying capacity” and “ecological habitat” concepts for soil microorganisms: farming practices affect soil microbial biomass either directly through resources availability or survival, and indirectly by changing the soil physical and chemical properties, i.e. habitat properties and growth conditions. By integrating findings from this extensive dataset, this work significantly expands the current understandings of how agricultural practices influence soil microbial biomass. It emphasizes the operational potential of soil microbial biomass as a practical, unifying indicator for assessing the impact of farming strategies on soil quality. Moreover, this study provides actionable insights to support sustainable land management and aligns international soil monitoring initiatives, including the European Directive on soil monitoring and resilience and its national implementations.