Application of Biochar-Immobilized for Enhancing Phosphorus Uptake and Growth in Rice.

Phosphorus (P) is an essential nutrient for rice growth, and the presence of phosphate-solubilizing bacteria (PSB) is an effective means to increase soil P content. However, the direct application of PSB may have minimal significance due to their low survival in soil. Biochar serves as a carrier that enhances microbial survival, and its porous structure and surface characteristics ensure the adsorption of . Inoculating rice husk biochar-immobilized with (BMB) resulted in dissolved inorganic and organic P levels of 39.55 and 31.97 mL L, respectively. Subsequently, rice pot experiments were conducted to investigate the response of soil microbial P mobilization and P uptake in rice to fertilizer inputs. The organic fertilizer (OF) combined with BMB treatment (MOF) showed the highest soil available phosphorus (AP) at 38 days, with a value of 7.83 mg kg, as well as increased the abundance while decreasing the abundance of bacterial communities compared with the control. Furthermore, the bioavailable P reservoir (HO-Pi and NaHCO-Pi) in soil was greatly increased through the fertilizer input and microbial turnover, with the highest HO-Pi (3.66 mg kg) in OF treatment and the highest NaHCO-Pi (52.65 mg kg) in MOF treatment. Additionally, carbon utilization analysis was applied using the commercial Biolog system, revealing that the MOF treatment significantly increased the utilization of carbohydrates, polymers, and amino acid carbon sources. Moreover, compared to the control, MOF treatment significantly increased the shoot (0.469%) and root P (0.516%) content while promoting root development and thereby supporting rice growth. Our study demonstrates that the MOF treatment displayed higher P levels in both soil and rice plants, providing a theoretical basis for further understanding the role of biochar-based bacterial agents in rice P management.