Excessive application of phosphate fertilizers exacerbates water pollution, while the low phosphorus availability in acidic soils results in diminished phosphorus utilization efficiency of crops. This study conducted a maize pot experiment to investigate the effects of soybean fermentation broth value-added phosphorus fertilizer (SFB-VAPF) on soil phosphorus availability and microbial communities in acidic lateritic red soils during the 31-day seedling stage to determine its growth promotion efficacy. Conducted in Guangzhou, China, under greenhouse conditions, the experimental design comprised 11 treatments: CK (no fertilizer), treatments with P alone at two levels (0.05 and 0.15 g·kg⁻¹), and eight SFB-VAPF treatments combining each P level with four dilutions of soybean fermentation broth (SFB; 100-, 300-, 500-, and 700-fold dilutions). Each treatment had five replications. Application of SFB-VAPF significantly improved the soil chemical attributes, enzyme activities, and promoted maize growth and nutrient accumulation. Compared to the high-P treatments (0.15 g·kg⁻¹ P), low-P SFB-VAPF demonstrated superior enhancement of the soil organic matter (SOM), available nutrients, maize biomass, and nutrient accumulation. The treatment combining 0.05 g·kg⁻¹ P and 100-fold diluted SFB significantly increased the acid phosphatase activity (ACP) by 28.01% and the AP content by 69.63%, while achieving the highest maize biomass. Although SFB-VAPF application reduced the microbial species richness, the combinations of low P with high SFB and high P with low SFB enhanced both the community structural diversity and distribution evenness. SFB-VAPF application reduced the abundance of Alphaproteobacteria, while the Gammaproteobacteria abundance significantly increased in the low-P SFB-VAPF groups. The microbial beta diversity analysis demonstrated that combining 0.05 g·kg⁻¹ P with SFB significantly altered the microbial community structure. The key driving factors included soil EC and SOM, AP, Al-P, and Fe-P contents, with AP content exerting an extremely significant influence on the bacterial community composition and structure (p ≤ 0.001). This study demonstrates that SFB-VAPF enhances soil phosphorus availability, and improves the structural diversity and distribution evenness of microbial communities, thereby promoting crop growth. Critically, SFB synergistically enhances the efficiency of low-concentration phosphorus fertilizers.

Soil acidification severely restricts agricultural productivity in red soil regions, and microbial remediation represents an eco-friendly restoration strategy. A pot experiment was conducted to investigate the dose-dependent effects of Pseudomonas fluorescens on acidified latosol, maize seedling growth, and rhizosphere bacterial communities. Five inoculation rates were applied (5.5 × 10⁹–3.3 × 10¹⁰ CFU pot⁻¹), together with a non-inoculated control. Pseudomonas fluorescens inoculation significantly increased soil pH and base cation contents, reduced exchangeable and hydrolytic acidity, and enhanced soil acid–base buffering capacity. Low to moderate inoculation rates promoted maize photosynthesis, root development, and nitrogen, phosphorus, and potassium accumulation, whereas the highest rate (3.3 × 10¹⁰ CFU pot⁻¹) significantly inhibited seedling growth. Bacterial sequencing showed that inoculation reshaped rhizosphere community structure and enriched taxa, including Proteobacteria, Bacillota, Bacillus, and Pseudomonas. Overall, inoculation rates of 1.1 × 10¹⁰ and 2.2 × 10¹⁰ CFU pot⁻¹ showed the most favorable responses across soil amelioration and maize growth-related traits, suggesting a suitable application range for acidified soil remediation. These results provide preliminary evidence that appropriate application of Pseudomonas fluorescens may contribute to the biological amelioration of acidified soils, although its field-scale effectiveness requires further validation.