【Objective】 To study the growth-promoting characteristics of a strain of Bacillus amyloliquefaciens SQ-2 isolated and screened in the laboratory, and to determine the concentration range, mechanism of action, and changes in soil microbiota induced by this strain to promote rice growth.【Method】 The phosphorus solubility and nitrogenase activity of strain SQ-2 were detected using the molybdenum blue colorimetric method and ELISA nitrogenase kit. Inoculating102, 104, 106, 108, and 3×108 CFU/mL bacterial suspension into hydroponic and soil cultured rice, the dry and fresh weight, length, and thickness of the roots and stems of hydroponic and soil cultured rice were measured, respectively after 14 and 20 d of cultivation. Meanwhile, the activities of urease, protease, and sucrase in soil cultured rice were determined using the phenol sodium hypochlorite colorimetric method, the ninhydrin detection method, and the 3,5-dinitrosalicylic acid colorimetric method. Besides, the soil pH value was determined using the pH meter potential method and the content of nitrogen, phosphorus, and potassium available in soil and the activity of acid phosphatase were detected by utilizing the corresponding reagent kit. Analysis of rhizosphere bacterial community structure in soil cultured rice soil was inoculated with 3×108 CFU/mL components.【Result】 The dissolution of tricalcium phosphate by strain SQ-2 was 229.63 mg/L, and the nitrogenase activity was 55.07 U/L. Compared with the control, the dry and fresh weight of hydroponic rice roots showed the most significant increase at an inoculum suspension concentration of 104 CFU/mL. At a vaccination concentration of 3×108 CFU/mL, the dry and fresh weight of soil cultivated rice rhizomes increased most significantly. As the concentration of the inoculum suspension increased, the activities of various enzymes and the concentration of available nitrogen, phosphorus, and potassium in the soil increased to varying degrees, the soil pH value while inoculating strain 3×108 CFU/mL decreased from 7.83 to 7.26. The inoculant strain SQ-2 changed the colony composition in the rice rhizosphere soil and significantly increased Ace, Chao, Sobs and Shannon indices of soil α-diversity.【Conclusion】 B. amyloliquefaciens SQ-2 had different growth promotion effects on soil culture and hydroculture rice. In soil culture experiments, the growth-promoting effect is notably pronounced through the augmentation of soil enzyme activity, rapid increases in available nitrogen, phosphorus, and potassium levels, and alterations in the soil microbial community structure. Overall, these experimental findings offer valuable insights into new strain resources for the development of bacterial fertilizer.
