Isolation And Identification Of Phosphate Solubilizing Bacteria In Subtropical Paddy Soil And Their Phosphorus Solubiling Effects And Mechanism

Phosphorus is one of the three essential nutrient elements for plant growth.Its effective supply determines the yield and quality of crops,and it is a basic resource for ensuring national food security.Phosphorus resources are typically non-renewable.As phosphate rock resources decrease year by year,the production and supply of chemical phosphate fertilizers are severely restricted.Therefore,phosphorus deficiency has become an important issue that threatens the sustainable development of agriculture and food security.Phosphate-dissolving microorganisms(biological fertilizers)have the potential to alleviate or even replace agricultural production's dependence on chemical phosphate fertilizers.The acquisition of high-efficiency phosphate-dissolving microorganisms and the discovery,enhancement and wide application of their phosphate-dissolving mechanism are the foundations,which have become the current research hotspots in this field.In this paper,paddy soil,a representative farming soil in the subtropical zone,is used as the material,starting from the isolation and screening of high-efficiency phosphate solubilizing bacteria,the phosphate solubilizing effect of the obtained phosphate solubilizing bacteria is explored,and the mechanism of phosphorus solubilization is revealed.The results of the study are as follows,which could provide some theoretical basis and guidance for effective use of P fertilizers:(1)Eight strains of phosphate-dissolving bacteria,namely Bacillus,Streptomyces,Rhodococcus and Methylorubrum;and 14 strains of phosphate-dissolving fungi,namely Penicillium and Talaromyces,Cladosporium,Sarocladium implicatum and Beauveria,were obtained and charaterized;among which,C7 and C26,2 strains belonging to bacteria Streptomyces and fungus Penicillium,respectively,were identified,and showed high phosphate-dissolving efficiency,In the pure culture system,the soluble phosphorus concentration increased to 317.86 mg/l and 1128.69mg/l,respectively.(2)Phosphorus solubilizing bacteria significantly increase the available phosphorus content of the soil.Phosphorus solubilizing bacteria in low-phosphorus,high-phosphorus and sterilized and unsterilized soils all promote the activation of soil phosphorus.Phosphate solubilizing bacteria affect the relative phosphorus content of the soil according to Hedley phosphorus system,reduce HCl-P and residual phosphorus,and increase available phosphorus(H₂O-P and Na HCO₃-Pi).In this paper,the dominant phosphate solubilizing bacteria C7 and C26 are characterized as facultative microorganisms,which have a strong ability to dissolve phosphorus in an aerobic pure culture system of calcium phosphate,and also exert a good ability to activate phosphorus in paddy soil cultivated in flooded water.Phosphorus solubilizing bacteria promote the conversion of soil phosphorus components,the stable state of phosphorus is transformed into intermediate and active state of phosphorus,and the intermediately active state of phosphorus is transformed into active state of phosphorus.(3)Phosphate solubilizing bacteria affect the physical and chemical properties of soil,phosphorus solubilizing bacteria have a time dependant effect on the promotion of soil phosphatase activity.RDA analysis and correlation analysis show that soil p H and DOC are the main factors that affect the activation of soil phosphorus by phosphorus solubilizing bacteria.The effective phosphorus concentration of the soil and the sterilization treatment affect the phosphorus solubilization effect of the phosphorus solubilizing bacteria in the soil,and the low phosphorus stress stimulates the phosphorus activation function of the soil phosphorus solubilizing bacteria.In the presence of indigenous microorganisms,phosphate solubilizing bacteria also exert a good phosphate solubilizing effect.(4)Phosphate solubilizing bacteria dissolve phosphorus by producing organic acids,releasing protons and phosphatase.At the same time,it is found that the cell wall of phosphate solubilizing bacteria has an erosion and adsorption effect on calcium phosphate.There is a significant negative correlation between H⁺and soluble phosphorus concentration in the pure culture system.Phosphorus-dissolving bacteria produce acid and dissolve phosphorus under low-phosphorus induction conditions.