increasing potassium (k) release from k-containing minerals in the presence of insoluble phosphate by bacteria

Introduction: phosphorus and potassium are major essential macronutrients for biological growth and development. application of soil microorganisms is one approach to enhance crop growth. some bacteria are efficient in releasing k and solubilizing p from mineral sources but their behavior was not studied more in presence together.materials and methods: in this study the ability of seven bacterial strains, including pseudomonas putida p13, p. putida tabriz, p. fluorescens tabriz, p. fluorescens chao, pantoea agglomerans p5, azotobacter sp. and bacillus megaterium jk3 to release mineral k from muscovite and biotite with application of insoluble (ca3(po4)2) or soluble (na2hpo4) psources was investigated. nutrient broth was used to prepare an overnight culture of bacteria to inoculate in aleksandrov medium, which was used to study the dissolution of silicate minerals. it should be mentioned that aleksandrov medium was used to determine the amount of released p from tricalcium phosphate (tcp) while muscovite was added to the medium as a sole source of potassium. concentration of p was determined spectrophotometrically by ammoniumvanadatemolybdate method and k was determined by flame photometry.results: the insoluble psource led to a significantly increased released k into assay medium (66%), and the net release of k from the biotite was significantly enhanced. among bacterial strains, the highest mean of released k was observed with p. putida p13 which released more k (27%) than the control. the amounts of released k from micas in the presence of insoluble and soluble phosphate by p. putida p13 were 8.25 and 4.87 mg/g, respectively.discussion and conclusion: application of insoluble phosphate could increase k release from mica minerals. the enhanced releasing of mineral k might be attributed to the release of organic acids from the bacteria, a mechanism which plays a pivotal role in solubilizing phosphate from inorganic source of phosphate.