The role of modified biochar in enhancing phosphorus (P) availability is gaining attention as an environmentally friendly approach to address soil P deficiency, a global agricultural challenge. Traditional phosphatic fertilizers, while essential for crop yield, are costly and environmentally detrimental owing to P fixation and leaching. Modified biochar presents a promising alternative with improved properties such as increased porosity, surface area, and cation exchange capacity. This review delves into the variability of biochar properties based on source and production methods and how these can be optimized for effective P adsorption. By adjusting properties such as pH levels and functional groups to align with the phosphate’s zero point of charge, we enhance biochar’s ability to adsorb and retain P, thereby increasing its bioavailability to plants. The integration of nanotechnology and advanced characterization techniques aids in understanding the structural nuances of biochar and its interactions with phosphorus. This approach offers multiple benefits: it enables farmers to use phosphorus more efficiently, reducing the need for traditional fertilizers and thereby minimizing environmental impacts, such as greenhouse gas emissions and P leaching. This review also identifies existing research gaps and future opportunities for further biochar modifications. These findings emphasize the significant potential of modified biochar in sustainable agriculture.

The application of slow-release fertilizer is an effective way to satisfy the demand for nutrients of crops. The objective of present study was to investigate the microbial community characteristics in rice rhizosphere soil under different fertilization modes of slow-release fertilizer. Three fertilization modes of slow-release fertilizer, i.e., (CK) manually broadcasted on the soil surface at 300 kg·ha⁻¹ before transplanting and then same fertilizer rate was applied at the same way one week after transplanting; (SF) 10 cm depth mechanized placement at 600 kg·ha⁻¹ during the transplanting; (DSF) 10 cm depth mechanized placement at 480 kg·ha⁻¹ during the transplanting, were adopt in the field experiment. The results showed that SF and DSF treatments promoted richness (ACE and Chao1 values) and diversity (Shannon value) of rice rhizosphere microorganisms compared with CK treatment. Compared with CK, SF treatment increased relative abundances of Planctomycetes and decreased relative abundance of Nitrospirae, DSF treatments increased relative abundances of Deltaproteobacteria. Moreover, higher relative abundances of Paenibacillus and Sphingomonas were recorded in DSF treatment than CK. In addition, the partial factor productivity (PFP) deep placement of slow-release fertilizer treatment was significantly higher than that of CK treatment. DSF treatment increased the yield by 16.61% compared with CK treatment while reducing fertilizer input by 20%. In conclusion, compared with broadcasting, deep placement of slow-release fertilizer could improve the structure, distribution, and diversity of the microbial community in rice rhizosphere soil, and increase the utilization rate of fertilizers, and increase rice yield.

Sulfur deficiency severely limits soybean growth, inhibiting the rhizobia nitrogenase and soybean protein synthesis. This study assessed the impact of sulfur fertilization and rhizobia inoculation on soybean growth and nitrogen fixation through bacterial culture and hydroponic experiments. We selected three rhizobia strains for bacterial cultures and used six sulfur levels. The test demonstrated severe inhibition of Rhizobium USDA110 growth without sulfur. In hydroponic experiment, we employed five sulfur levels with USDA110 as the inoculum strain. Soybean growth, nitrogen fixation, yield, and root morphology-related parameters, and root nodule growth, were significantly inhibited without sulfur. Following Rhizobium inoculation, low sulfur concentrations (0.15–0.60 mM) stimulated early-stage (V9) root growth and increased shoot nitrogen accumulation, but inhibited root growth at R5 stage. Furthermore, Rhizobium inoculation notably enhanced soybean growth, nitrogen fixation, and yield, especially within the recommended low sulfur concentration range (0.15–0.30 mM). The maximum nodule nitrogenase activity at R5 stage and highest yield was recorded at a 0.3 mM sulfur concentration with Rhizobium inoculation, which was 9.51–1222.07% higher than other treatments. These findings highlight that low sulfur concentration and rhizobia inoculation enhance soybean growth, nitrogen fixation, and yield but reduce soybean root efficacy, increasing reliance on root nodules.

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.