Effects of Long-Term Material Amendments on Phosphorus Fractions and Associated Microbial Changes in Greenhouse Tomato Soil

Background and Aims: High phosphorus (P) fertilizer application is common in facility vegetable production, often leading to P fixation. Organic-inorganic materials may im-prove soil P availability, but their long-term effects and microbial mechanisms in con-tinuous cropping soils are not well understood.Methods: We analyzed the effects of different materials on the chemical properties of facility vegetable soils, phosphorus fractions, phosphorus-related enzyme activities, and microbial communities, particu-larly the phoD and pqqC genes.Results: Biochar (BCa) and biochar combined with cal-cium (BRCa) treatments significantly increased soil pH, while the BRCa treatment also enhanced soil organic matter (SOM) content. All treatments improved available P (AP), total P (TP), alkali-extractable N (AN), microbial biomass P (MBP), and labile P, while reducing medium-labile and residual P. Activities of alkaline phosphatase (ALP), py-rophosphatase, and phytase were also elevated. BRCa treatment caused significant shifts in the phoD and pqqC microbial communities. SEM models showed that these materials positively impacted labile P (LP) and facilitated the conversion of medi-um-labile P (MLP) to LP.Conclusion: Adding materials like straw, biochar, and calcium enhances soil P availability by altering both soil properties and microbial communities, with optimized material combinations offering an effective strategy for efficient P management in facility agriculture.