Survival of a Phosphate Solubilizing Microorganism in Ion-Sterile Carriers

Abstract

A cold-tolerant phosphate solubilizing bacterium (PSB) was isolated from roots of ryegrass (Lolium perenne L.). Studies involving phosphate solubilization in liquid culture and survival of the PSB in nonsterile zeolite, leonardite, peat, rock phosphate, and an organic fertilizer were performed. The PSB was able to dissolve 163 ppm P with a simultaneous fall in pH (from 7.7 to 5.7) in Pikovskaya’s medium during a ten-day incubation. The number of PSB declined logarithmically in 28 oC incubation regardless of the carrier. The rate of decrease in PSB population was less pronounced in zeolite. However, the PSB’s population density increased up to 109 cfu g-1, and stayed in the range of 108 to 109 cfu g-1 in zeolite and rock phosphate after 13-weeks of storage at +4 oC. The contaminant microorganisms also grew in the carriers, with population densities ranging between 108 to 109 cfu g-1 at week-9. The suppression of the local microorganisms is required to increase the quality of organic fertilizer by the addition of PSB. Zeolite could be a good carrier, due to its large surface area and porosity, which allow high number of microorganisms to occupy.