Enhanced Fe-bound phosphate availability by the combined use of Mg-modified biochar and phosphate-solubilizing bacteria

The formation of insoluble phosphate in soils and resulting overfertilization causes a large environmental risk. Although phosphate-solubilizing bacteria (PSB) can solubilize Ca-bound phosphate well by acidification, they often have a low capacity to solubilize Fe-bound phosphate (Fe-P). In this study, a novel Mg-modified lignin biochar (MB) was prepared via the chemical impregnation method to improve the ability of PSB to dissolve FePO4. The results show that dissolved phosphate rapidly increased to approximately 0.9 mM over 3 days in the FePO4 + PSB + MB system. The system with MB was more effective to increase FePO4 dissolution by 17 times and increase the amount of organic acids production by 2 times than that without the MB. The characterization results indicated that the polymerization and rearrangement of FePO4 occurred when the FePO4 particles attached to the surface of the MB, resulting in the formation of Fe(III)(2)Fe(II)(P2O7)(2) crystals on the surface of the MB. The Mg on the surface of the MB can induce the preferential orientation of the [210] crystal plane of the Fe(III)(2)Fe(II)(P(2)O7)(2), which can be preferentially dissolved by PSB, causing an increase in Fe-P solubility. This study provides a new method for the development of insoluble phosphate solubilization technology to limit the overfertilization of soil and offers a clear understanding of the interactions among biochar, Fe-P, and PSB.

Automated summary

In this study, a novel Mg-modified lignin biochar (MB) was prepared to improve the ability of phosphate-solubilizing bacteria (PSB) to dissolve FePO4. The results showed that the system with MB was more effective in increasing FePO4 dissolution and organic acid production. Characterization results revealed the formation of Fe(III)(2)Fe(II)(P2O7)(2) crystals on the surface of MB, which increased the solubility of Fe-P. This study provides a new method for the development of insoluble phosphate solubilization technology.