RESUMO
AIM: Potassium (K) is one of the three major nutrients required of plant growth and muriate of potash (MoP) is the only recognized chemical fertilizer used in agriculture. In many countries, 100% of the applied MoP is imported costing huge revenue. Application of suitable potassium-solubilizing bacteria (KSB) as biofertilizer could be an integral part of K management in arable soil. The object of this study was to evaluate K-solubilizing ability of a ubiquitous micro-organism as KSB to supplement K in soil. METHODS AND RESULTS: Strain (O-5) was isolated from tea-growing soil and identified as Bacillus pseudomycoides. Phylogenetic analysis revealed that the nearest neighbours of B. pseudomycoides strain O-5 were Bacillus cereus, Bacillus thuringiensis and Bacillus toyonensis. Though the species was first identified in 1998 and is ubiquitous in soil, the role of this group of micro-organisms in nutrient cycling in soil has not been studied before. Strain solubilized 33·32 ± 2·40 µg K ml-1 in mica waste (MW; muscovite type mineral)-amended broth after 7 days incubation at 30 ± 1°C. In a soil microcosm study under laboratory condition, B. pseudomycoides strain O-5 increased K availability by 47·0 ± 7·1 mg kg-1 after 105 days incubation, while the strain released 104·9 ± 15·3 mg K kg-1 in MW-treated soil. In this study, application of isolated B. pseudomycoides with MW significantly increased K availability in soil, and that in turn facilitated K uptake by tea plants. CONCLUSION: Based on the data, it could be inferred that B. pseudomycoides could mobilize K from bound form in soil and can be utilized as K-solubilizing biofertilizer especially in combination with MW for supplementing K in soil. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacillus pseudomycoides strain O-5 has potential to be used as K-solubilizing biofertilizer in agriculture.
