Phosphorus fractionation in some soils of Saudi Arabia

Abstract

Total amounts of phosphorus and quantities in the organic form and in various fractions of the inorganic form were determined in samples of surface layers of nine soils from five major agricultural areas of Saudi Arabia (Al-Hasa, Qassim, Wadi Dawasir, Al-Kharj and Taif). Total phosphorus ranged from 182 to 1088 ppm and organic phosphorus from 0 to 90 ppm. Among the fractions of inorganic phosphorus Ca-P was much the largest portion, ranging from 182 to 902 ppm. Al-P and occluded P were so low as to be negligible, whereas Fe-P and residual P were present in slightly larger amounts. Amounts of phosphorus extracted by NaHCO 3 were below critical levels, according to observations elsewhere. Amounts of total P in four soil samples were lower than values reported for the soils of the western United States and Lebanon. Generally low amounts of organic phosphorus appear to be closely related to the organic matter contents of the samples.