Microbial Bioinoculation as an Effective Strategy to Enhance Plant Potassium Uptake for Sustainable Agriculture

The present investigation was conducted to isolate and characterize potassium-solubilizing bacteria and to determine their potassium mobilization potential using in vitro assays and pot experiments. Among the soil-derived isolates, strain AOB28 showed a high K-solubilizing potential, reaching 50.09 mg L⁻¹ K relative to the uninoculated treatment. The K-solubilization capacity of the strain was further evaluated under varying environmental conditions, revealing maximum K release at 40°C, pH 6, and a mica concentration of 9 g L⁻¹. The enzymatic profile of strain AOB28 revealed notable amylase and protease activities, along with detectable CMCase activity, and the strain displayed considerable tolerance to both salt and heavy metals, supporting its suitability for biotechnological applications. Pot experiments demonstrated that bacterial inoculation significantly enhanced plant growth relative to the uninoculated control, as evidenced by a 62% increase in dry matter accumulation. In parallel with enhanced biomass production, bacterial treatment substantially modified mineral nutrient uptake. Notably, AOB28 B. subtilis enhanced K uptake in arugula plant grown under pot conditions (+ 63.5%), markedly decreased Ca uptake (-29%), and moderately increased Mg and P uptake (+ 19% and + 27%, respectively). For micronutrient accumulation, Mn and Zn increased significantly by 37.9% and 42.6%, respectively, in AOB28-treated plants, whereas Fe and Cu uptake were not statistically significant. Among the evaluated nutrients, potassium exhibited the most pronounced response, indicating that improved K acquisition was a key contributor to the observed growth stimulation and corroborating the results obtained from the in vitro solubilization assays. These findings suggest that such bacterial strains could be used in balanced fertilization strategies for arugula, but their application should be carefully managed, and further research is needed to understand their mechanisms and broader potential in agriculture.