Biochar promotes the dissolution of inorganic inactive phosphorus by mediating the bacterial community during corn stover and cattle manure composting.

Phosphorus (P) is a macroelement primarily found in insoluble forms in nature. Enhancing the effectiveness of P is crucial for sustainable agricultural development and ecosystems. The research employed a combination of sequential extraction methods, high-throughput sequencing techniques, microbial culturing, and ecological network analysis of bacterial communities, along with module comparison, to explore the dynamics of different P fractions in calcareous soils. The objective of incorporating biochar into the composting of maize stover and cattle dung was to uncover potential microbial processes that could facilitate the activation of inorganic non-labile P. Findings revealed that during the composting process with biochar, bacterial populations played three distinct roles in the transformation of inorganic non-labile P compounds (such as occluded P and Ca10-P). Primarily, the introduction of biochar significantly increased both the diversity and abundance of bacterial communities. Additionally, it enhanced the ability of phosphate-solubilizing bacteria to maintain the structure of bacterial ecological networks by boosting their complexity, interconnectedness, and stability. Moreover, the incorporation of biochar stimulated the P-related metabolic activities within the bacterial community, significantly enriching key metabolic pathways such as the citrate (TCA) cycle, glycolysis/gluconeogenesis, the pentose phosphate pathway, galactose metabolism, starch, and sucrose metabolism, as well as the metabolism of amino and nucleotide sugars. Moreover, biochar addition intensified the connections between key operational taxonomic units (OTUs) and non-labile P while simultaneously increasing the total organic carbon concentration and enhancing alkaline phosphatase activity. This study provides valuable insights for enhancing P effectiveness in calcareous soils.