Enhancing Soil Colloidal Phosphorus Bioavailability by a Plant-Derived Synergist

As a critical replenishment source for depleted phosphate in the rhizosphere soil, colloidal phosphorus (P_coll) of varied sizes has attracted more research interest; however, how to convert P_coll among subfractions to enhance soil P bioavailability remains unclear. In this study, we combined the variation of the microbial community, the distribution of diffusive gradient in thin films (DGT)-labile P and acid phosphatase, and the changes of four subfractions of P_coll to reveal the mechanism of the P synergist derived from plants, improving the soil P bioavailability. Results showed that the P bioavailability could be enhanced via (1) transformation from the coarse-sized colloidal P (CC, 450–1000 nm) and medium-sized colloidal P (MC, 220–450 nm) to fine-sized colloidal P (FC, 20–220 nm) and nanosized colloidal P (NC, 1–20 nm) in soil and interstitial water through reductive dissolution by microorganisms and release of highly bioavailable phosphate themselves and (2) hydrolyzation from organic P to inorganic P by microorganisms. The rice cultivation experiment showed that soil treated with a P synergist positively affected crop growth. All the above-suggested plant-derived P synergist provide a reliable and promising solution for enhancing soil P_coll bioavailability.