تلخیص
Phosphorus management in agriculture involves acquirin8 exact and comprehensive information about the fate of added phosphate ta the soil. A great part of a phasphate (P) fertiliser is retained on the surface of variable- charge minerals through specific adsorption,- the precipitation process takes place in the limited space around the fertiliser grains where its concentration is high. We tested the ability of three Pseudomonas strains ta release P from iron (III) hydroxide. Iron hydroxide precipitated on filter paper, was used as a variable-charge mineral and P was loaded on it. The siderophore and M production, acid and alkaline phosphatases activity were assayed in vitro. All three isolates released P as compared to controls with killed bacteria or without bacteria. The amount of released P from iron hydroxide were 50.5, 29.2 and 61.6Wo for P. putida, P. fluorescens Chao and P. fluorescens Tabriz, respectively. The amount of P in solution phase was highest (0.74 mg P/50mL) with P. putida and lowest (0.32 ITI8 %50 mL) with P. fltiorescens Tabriz. The highest P assimilation from total P released was in P. fluorescens Tabriz. In vitro tests revealed that the P. fluorescens Chao with significantly higher sideraphare production and phosphatases activity, had the least effect on P release from iron hydroxide, while two other isolates had significantly higher M production. It seems that the M production is the main mechanism of P released from variable charge minerals and P. putida was the most efficient bacterium.
A. Ghaderi ,, N. Aliasgharzad", , S. Oustan', P.A. Olsson’. (2008) Efficiency of three Pseudomonas isolates in releasing phosphate from an artificial variable-charge mineral (iron III hydroxide), The Journal Soil & Environment , Volume 27, Issue 1.
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