Potassium-Solubilizing Activity of Bacillus aryabhattai SK1-7 and Its Growth-Promoting Effect on Populus alba L.

In the present study, the potassium-solubilizing characteristics of Bacillus aryabhattai SK1-7 and its growth-promoting effect on plants were evaluated to determine the biotechnological potential of this bacterium in alleviating soil potassium deficiency. The potassium-solubilizing activity of SK1-7 was determined by fermentation. Additionally, the fermentation broth was determined by flame spectrophotometry. The aluminum and silicon ion contents in SK1-7 fermentation broth were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) after digestion with nitric acid hydrogen peroxide hydrofluoric acid. Scanning electron microscopy (SEM)-based observations were performed to assess the morphological changes in potassium feldspar surfaces digested by potassium-solubilizing bacteria. In addition, the effects of SK1-7 on plant growth and soil physical and chemical properties were analyzed. After incubation for 7 days in a potassium-solubilizing medium, the concentration of potassium dissolved reached 10.8 mu g/mL and the percentage of potassium released was 32.6%. The pH rapidly decreased from 7.2 to 4.321 within the first day and then further decreased to 3.90 after 7 days. After 7 days, the concentrations of aluminum and silicon in the fermentation broth were 1.01 and 24.19 mu g/mL, respectively. The growth promotion assay results showed that SK1-7 has good growth-promoting effects on poplar and can effectively improve the available potassium content in poplar rhizosphere soil. The SK1-7 strain can effectively dissolve insoluble potassium to release soluble potassium ions and clearly promotes the growth of poplar after being applied to soil. Thus, the SK1-7 strain is a potassium-solubilizing microorganism with good application prospects.