Contrasted phosphorus mobilization strategies between upland and paddy soils: insights from phosphorus biologically factions and functional gene profiling

Soil phosphorus (P) availability and microbial community are typically affected by agricultural land use. This study aimed to explore the link of soil available P and P-cycling-related bacteria and to distinguish P mobilization strategies between upland and paddy cropping systems.

A total of 120 soil samples were collected from 60 sites with adjacent upland and paddy soils in subtropical China. we analyzed soil P fractions and investigated bacteria-mediated P cycling by quantifying the abundance of genes involved in organic P (Po) mineralization (phoD, phoX, phoC), inorganic P (Pi) solubilization (pqqC, gltA), and P transport (pitA, pstS).

The abundance of P-cycling-related bacteria genes was significantly higher in paddy soils compared to upland soils. CaCl₂-P, and enzyme-P levels were notably higher in upland soil. In upland soil, microbes harboring Po-mineralizing and Pi-solubilizing genes contributed indirectly to P availability by mobilizing enzyme-P. In paddy soil, citrate-P was strongly correlated with available P, suggesting that P availability is mainly controlled by organic acids released from root exudation and microbial activity.

The microbes mainly affected P availability via Po mineralizing in upland soil. In contrast, microbes tend to secrete organic acids to mobilize Pi in paddy soil.