29 / 2023-04-29 14:03:29

Study on interaction between biochar-based phosphate fertilizer and phosphorus-dissolving bacteria and its effect on soil phosphorus transformation

biochar-based phosphate fertilizer; phosphorus-dissolving microorganism; microwave co-pyrolysis; phosphorus availability.

The amount of fertilizer application is increasing year by year in the world, but the problems of soil compaction, soil degradation and micro-ecological destruction caused by improper fertilization are becoming more and more serious. Biochar-based phosphate fertilizers (BPFs) are prepared by pyrolysis of biomass and phosphorus containing minerals. They have broad application prospects because of their strong sustainability and high nutrient utilization. However, the traditional pyrolysis method has high energy consumption and cannot control the nutrient content in BPFs. In addition, the prepared BPFs contain high ineffective phosphorus, such as precipitated phosphorus and organic phosphorus. In this study, BPFs with controllable nutrient structure were prepared by using cotton stalk (CS), K3PO4 and MgO as pyrolysis raw materials and microwave radiation as pyrolysis mode. Then, biochar-based insoluble-phosphate fertilizer (NBPF) was prepared by regulating the proportion of cotton stalk, K3PO4 and MgO, and combined with phosphorus-dissolving bacterium Enterobacter hormaechei RS-198 to explore the mechanism of RS-198 absorption and transformation to phosphorus in NBPF and enhance the effectiveness of precipitated phosphorus and organic phosphorus in NBPF.

NBPF prepared with the mass ratio of CS, K3PO4 and MgO of 1: 0.5: 0.5 has a high proportion of precipitated phosphorus (65.9%) and organic phosphorus (24.3%). Precipitated phosphorus is attached to the surface of NBPF to make it rough, and micro-level macropores in NBPF provide sites for the attachment of RS-198. In addition, the low content of free radicals in NBPF had no toxic effect on RS-198, and its high content of liable carbon accelerated the colonization rate of RS-198. RS-198 is well attached to the surface of NBPF and activates the precipitated phosphorus and organic phosphorus in NBPF. Then, RS-198 stored activated P in the form of PolyP and released under the condition of external phosphorus starvation, which transform and release the phosphorus in NBPF.