Isolation and identification of potassium‐releasing bacteria in soil and assessment of their ability to release potassium for plants

Summary The application of potassium (K)‐releasing microorganisms is a promising approach for increasing K availability in soil. The objectives of this study were to isolate and characterize the K‐releasing bacteria (KRB) and to evaluate their contribution to the solubilization of K from muscovite and biotite, and to the assimilation of released K by tomato in a pot culture experiment. Soil samples were screened in both solid and liquid Aleksandrov media to isolate bacteria with the potential to release K from biotite and muscovite. Our results from in‐vitro experiments revealed that more K was released in treatments with KRB than in the uninoculated media (control). Under the best conditions an increase of 188 and 127% was obtained for biotite and muscovite, respectively; among the isolates with the largest releasing ability it was 49 mg l−1. The most efficient bacteria were identified as the Pseudomonas genus. Results of the pot culture experiment showed that the concentration and content of K in plant tissue were considerably more than those in any of the controls with no living organisms present. Results revealed that significantly more biomass was accumulated and K acquired in most pots treated with bacterial strains than in the control, especially for Pseudomonas sp. strain S10‐3. This treatment increased K concentation and content by more than 50 and 70%, respectively, in tomato aerial tissue. Further research is necessary to examine the effects of these bacterial strains on the mobilization of K‐bearing minerals under field conditions. Highlights The aim was to determine if bacterial isolates can accelerate K release from micas for plants. We investigated the potential of some isolated bacteria to solubilize K from muscovite and biotite. Identification of efficient isolates showed that KRB belonged to the Pseudomonas genus. Pseudomonas sp. strain S10‐3 increased K concentration in tomato aerial tissue by more than 50%.