Phosphorus Fractions in some Calcareous Soils of Egypt as Affected by Aging and their Properties

doi:10.21608/ejss.2013.191

Phosphorus Fractions in some Calcareous Soils of Egypt as Affected by Aging and their Properties

Document Type : Original Article

10.21608/ejss.2013.191

Abstract

IDENTIFYING the predominate individual forms of inorganic P in soils is helpful in the determined potential availability of P in calcareous soils. Therefore, the current investigation was conducted to study the distribution of P amongst the different fractions of some calcareous soils as affected by the period of soil cultivation and also the extent to which some soil properties affect such a distribution. Fulfilling such objectives was executed by carrying out a P fractionation experiment whose results showed that AB-DTPA extractable fraction (available) was highly and significantly affected by Fe,Al-P fraction. Ca-P fraction was very much greater than the other P-fractions in all the investigated soils. Within all the investigated soils, the Fe-Al-bound fraction contained P in concentrations far lower than the Ca-bound fraction. Occluded- P was found in the lowest concentrations. The residual P fraction was found in quantities almost equal to or even exceeding the other total extractable fractions. Fe, Al-P fraction correlated at a high level of significance with each of the occluded-P and residual-P fraction as well as the total-P content. This means that Fe, Al-P fraction can be under certain circumstances converted to either of both of occluded and residual fractions. Occluded-P fraction showed highly significant correlations with each of Fe, Al-P and residual-P fractions and at the same time, it correlated but only at a significance level of 5% with total-P. Non- of the investigated P-fractions was affected by either of the studied properties solely but more than of these properties contributed together to affect the different soil P fractions. For example, Fe, Al-P correlated significantly with sand, silt, CaCO₃ and EC while each of the occluded-P, residual-P and total-P content showed significant correlation with CaCO₃, EC and CEC together. Ca-P fraction was affected by sand, clay and EC. The relationships between AB-DTPA extractable fraction (the available P fraction) and the different soil properties indicate that both silt and CaCO₃ contents significantly and negatively affected the AB-DTPA extractable P. It can be deduced that the different soil properties, although varied in their contribution to determine the amount of AB-DTPA extractable P, yet the role of either of these properties cannot be neglected.

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