Phosphate-solubilizing microorganisms regulate the release and transformation of phosphorus in biochar-based slow-release fertilizer

Coupling phosphate-solubilizing microorganisms (PSM) can improve the availability of phosphorous (P) in biochar-based slow-release P fertilizers (BPF). However, the mechanism in release and transformation of P in BPF regulated by PSM is still unclear. Herein, the biocompatibility and the adhesion behaviors of BPF and PSM (Enterobacter hormaechei Rs-198) in soil were firstly studied, and a 90 days' laboratory-scale soil incubation experiment of BPF and Rs-198 was performed to study the transformation of P of BPF. The results show that BPF has a good biocompat-ibility for Rs-198 due to its low aromaticity, graphitization and free radicals' content (0.084 mg/g). Rs-198 are adhered to the surface of BPF in soil due to the high negative secondary energy minimum and low total interaction energy be-tween Rs-198 and BPF. Available P in the incubation of BPF and Rs-198 (BR treatment) is significantly higher than that of the incubation of BPF (BF treatment) at initial 60 days. However, the content of available Pin BR treatment is much lower compared with that in BF treatment on day 90, which is attributed to the entrapment of released P from BPF by Rs-198 and the formation of polyphosphate (polyP) rather than bound with soil mineral. Overall, this study presents new insights into the transformation of P in BPF regulated by PSM.

Automated summary

Coupling phosphate-solubilizing microorganisms (PSM) with biochar-based slow-release P fertilizers (BPF) can enhance the availability of phosphorous (P). However, the mechanism of P release and transformation in BPF regulated by PSM is still unclear. In this study, the biocompatibility and adhesion behaviors of BPF and PSM (Enterobacter hormaechei Rs-198) in soil were investigated. A 90-day incubation experiment was conducted to study the transformation of P in BPF. Results showed that BPF had good biocompatibility with Rs-198 and Rs-198 adhered to the surface of BPF in soil. The available P in the incubation of BPF and Rs-198 was significantly higher than that of BPF alone until day 60, but decreased on day 90 due to entrapment by Rs-198 and the formation of polyphosphate.