Mohammad Reza Sarikhani - Department of Soil Science, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
Mitra Ebrahimi - Department of Soil Science, Faculty of Agriculture, Bu Ali Sina University, Hamedan, Iran
Shahin Oustan - Department of Soil Science, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
Naser Aliagharzad

Environmental crisis around the world increases the awareness of people regarding the effects of hazardous materials. Chemical fertilizer, for example, is considered potentially harmful to nature and human. But there are alternative options to meet plant growth demand, especially use of soil microorganisms. Potassium is one of the essential nutrients and plays an important role in the growth and development of plants. Biofertilizer is a good platform to deliver this primary macronutrient by assistance of Potassium Solubilizing Bacteria (KSB). On the other hand, KSB are able to solubilize rock potassium minerals through production and excretion of organic. In this study the ability of seven bacterial strains including Pseudomonas putida P13, P. putida Tabriz, P. fluorescence Tabriz, P. fluorescence Chao, Pantoea agglomerans P5, Azotobacter sp. and Bacillus megaterium JK3, were tested to investigate the releasing of mineral K from muscovite and biotite under application of insoluble (Ca3(PO4)2) or soluble (Na2HPO4) P-sources. Our results showed that, insoluble P-source led to a significant increase of released K concentration in assay medium (66%), and the net release of K from the biotite was significantly enhanced. Among bacterial strains highest mean was observed with P. putida P13 and released more potassium (27.24%) in comparison to the control. The amounts of released K from micas in presence of insoluble and soluble phosphate were 8.25 and 4.87 mg/g for P. putida P13, respectively. In this study we showed that application of insoluble phosphate could increase releasing of potassium from micas minerals. The enhanced releasing of mineral K might be attributed to the release of organic acids from the bacteria, the mechanism which plays pivotal role in solubilizing of phosphate from inorganic source of phosphate.

K-solubilizing bacteria, Potassium, K containing minerals, Pseudomonas