The global positive effect of phosphorus addition on soil microbial biomass

Soil microorganisms play key roles in maintaining terrestrial biodiversity and ecosystem processes. While phosphorus (P) input into soils has been elevated due to anthropogenic activities in the past decades, how soil microorganisms respond to P addition remains unclear with diverse experimental results. By conducting a global meta-analysis with paired observations of soil microbial attributes from 119 studies, we showed that P addition globally increased microbial biomass by 7.3%. Fungal biomass and microbial P also significantly increased while microbial C:P and N:P ratios decreased with P addition. We highlighted the enhanced plant belowground biomass by P addition as a key mechanism for the positive response of soil microbial biomass. The P addition effect on microbial biomass was consistent among different ecosystem types and climates while being more positive in P-limiting soils. Our results underline that P addition may be an important approach for improving soil microbes and associated functions.