Evaluation of the Status of P Fractions and their Relationships with Selected Soil Properties in Some Calcareous Soils

Effective soil phosphorus (p) management requires the understanding of p forms and its availability. the amount and distribution of p in different fractions of 15 soil samples of fars province, iran were determined by sequential extraction methods. the relationships of the p distribution among each other and with soil characteristics were investigated. total p of different soils ranged from 349 to 994.3 cmol.kg^-1. the clay contents of different samples ranged from 18% to 53%, cec from 8.5 to 24.9 (cmol(+)kg^-1) and the cce from 20.6% to 64%. the amount of different p forms ca2-p (dicalcium phosphates), ca8-p (octacalcium phosphates), al-p (alphosphates), fe-p (fe-phosphates) and p as ca10-p (apatite) were determined. the relative abundance of other inorganic p forms was in the order of ca10 – p > ca8- p > al –p> fe-p>ca2-p > occl-p. simple correlation coefficients showed that olsen-p had a significant correlation with total-p, ca2-p, ca8-p and al-p. a significant correlation was also observed between the p forms, which is presumably a reflection of the existence of a dynamic relation between the chemical forms of phosphorus in soil. clay with total-p and apatite; total p with olsen, al-p and organic-p; cec with total-p and organic-p have positive significant correlation. sand with ca10-p and al-p; organic-p and al-p with ph have negative significant correlation.