شكل هاي مختلف فسفر در برخي خاك هاي آهكي استان فارس و رابطه آنها با ويژگي هاي فيزيكوشيميايي خاك

Knowledge of forms of phosphorus (P) is important in the evaluation of soil P status and also in understanding soil genesis and fertility. Amounts and distribution of P in different organic and inorganic fractions were examined in 39soil samples of Fars province. Soils were sequentially extracted to determine organic P and inorganic P fractions. Total P with an average of 597 mg/kg soil was lower in the light soils (482 mg/kg) as compared with the heavy soils(690 mg/kg). Organic P constituted considerable portions of TP (27%). Calcium phosphates with an average of 424 mg/kg soil and being comprised of 71% inorganic P was the dominant form of soil phosphorus. Simple regression analysis indicated that there were significant positive relationships between organic P, Ca phosphates and AI-Fe phosphate values with CEC and clay content. Stepwise multiple regression analysis showed that a combination of soil properties such as clay content and equivalent calcium carbonate (CCE) increased correlation coefficients (R). Alghough multiple regression model was significant (at P<0.05), the relative contribution of each soil property in Al-Fe-P fraction was not considerable.