Phosphate Adsorption Characteristics in Five Major Soils Groups

Abstract

Phosphate adsorption was investigated over the pH range 3 - 9 and at various equilibrium phosphate concentrations in five major soils groups; Brackish Water Alluvial soils (BMA) (Acid Sulphate), fresh Water alluvial soils (FWA), Reddish Brown Lateritic Soil (RBL), Grumusols and , Noncalcie Brown soils (NCB).
Phosphate adsorption in teh BWA reached a maximum at about pH5 and was associated with the formation of a surface chelating compound with hyxroxy-aluminium, with increased phosphate concentration there was a marked increase in adsorption. In the Grumusols which have a high level of calcium carbonate, the phosphate precipitated out as calcium phosphate; increased phosphate levels resulted in an increasel level of precipitation. In teh FWA soil group phosphate adsorption was at a maximum at about pH4 and decreased with increasing pH. In the ramaining two soils groups, RBL and NCB, the level of phosphate adsorption was generally low and reached a maximum at about pH 4.