Abstract
<p>A cold-tolerant phosphate solubilizing bacterium (PSB) was isolated from roots of ryegrass (<em>Lolium perenne</em> L.). Studies involving phosphate solubilization in liquid culture and survival of the PSB in non-sterile 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 <sup>o</sup>C 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 10<sup>9</sup> cfu g<sup>-1</sup>, and stayed in the range of 10<sup>8</sup> to 10<sup>9</sup> cfu g<sup>-1</sup> in zeolite and rock phosphate after 13-weeks of storage at +4 <sup>o</sup>C. The contaminant microorganisms also grew in the carriers, with population densities ranging between 10<sup>8</sup> to 10<sup>9</sup> cfu g<sup>-1</sup> 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.</p>
Highlights
Phosphorus (P) is an essential plant nutrient.most of the soil-P is in hardly available forms to plant, water soluble P-fertilizers are commonly used in agriculture
Most of the soil-P is in hardly available forms to plant, water soluble P-fertilizers are commonly used in agriculture
The initial increase in available-P coincided with the decrease in pH, suggesting presence of organic acid(s) produced by the phosphate solubilizing bacterium (PSB)
Summary
Phosphorus (P) is an essential plant nutrient.most of the soil-P is in hardly available forms to plant, water soluble P-fertilizers are commonly used in agriculture. Undergoes a serious of reaction, precipitating as Ca- and Mg-phosphates in alkaline soils; and Feand Al-phosphates in acid soils. These ions are adsorbed to surfaces of soil constituents, another way within which the availability of additional-P is reduced. The mechanism, by which the microorganisms solubilize the hardly soluble-P has generally been recognized as therelease of organic acids and subsequent dissolution of tri-calcium phosphates (Babu-Khan et al 1995; Gyaneshwar et al 1999; Krishnaraj et al 2001; Liu et al 1992; Rodriguez et al 2004)
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