Biochar Promotes Phosphorus Solubilization by Reconstructing Soil Organic Acid and Microorganism Networks

Biochar has the ability to enhance the solubilization of phosphorus (P) in soil. Nonetheless, the role played by organic acid and microorganism in P solubilization under biochar application conditions remains unclear. In this study, we examined the relationship between soil organic acids and microorganisms, as well as P fractions, following the addition of biochar, utilizing foxtail millet, maize, soybean, and mung bean as materials. The results demonstrated that the addition of biochar increased the availability of P by increasing the content of the resin-P fraction and decreasing the content of the NaOH-Pi, NaOH-Po, and HCl-P fractions in the soil. In addition, resin-P fractions were elevated by 142.78%, 95.27%, 35.99%, and 21.55% in the soils of foxtail millet, maize, soybean, as well as mung bean, respectively. In the microorganisms, the addition of biochar promotes P conversion by increasing the number of labile-P-associated microorganisms and decreasing the number of moderate-labile-P- and non-labile-P-associated microorganisms. In the organic acids, biochar expanded the biological pathways for the solubilization of moderate-labile-P through organic acids. This study illustrates the potential mechanism of biochar to enhance soil P availability.