Shelf life of phosphate-solubilizing inoculants as influenced by type of carrier, high temperature, and low moisture

Abstract

A charcoal–soil mixture, paddy straw compost, and wheat bran were tested to explore their possible use as carriers for phosphate-solubilizing bacteria and fungi. The charcoal–soil mixture was found to be the best carrier for phosphate-solubilizing bacteria, and wheat bran, for phosphate-solubilizing fungi. Higher temperatures during storage markedly influenced the shelf life of phosphate-solubilizing microorganisms. Thermotolerant strains, such as Bacillus subtilis, Bacillus circulans, and Aspergillus niger, were found to survive not only at high storage temperatures (40 and 45 °C), but also at low moisture status in the carrier. Key words: inoculum carriers, thermotolerant strains, shelf life.