Phosphate Adsorption By Some Rhodic' Ferralsols (Ultic Haplustox) From Tanga, Tanzania.

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Date
1991
Authors
Aaup R. H.
Mrema J. P.
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Abstract
The amounts of phosphate adsorbed by seven soils (Rhodic ferralsols) increased with increasing levels of added phosphate. In the range 0-400 ILg P/g soil added phosphate, more than 88 % of the phosphate was adsorbed by the soils indicating the availability of phosphate adsorption sites on the soil colloids. Above 400 ILg PIg soil added phosphate, the amounts of phosphate adsorbed increased at a gradual decreasing rate to about 50% at 2000 ILg PIg soil added phosphate indicating the gradual saturation of the phosphate adsorption sites on the soil colloids. The similarities in the trends of the amounts of the phosphate adsorbed by the soils were attributed to the close similarities in the properties of the soils. The plots of the phosphate adsorption data according to the Langmuir, Freundlich and Temkins equations were not linear indicating that phosphate adsorption by the soils is a combination of true adsorption and other mechanisms like specific anion and ligand exchange and precipitation reactions. At very narrow concentration ranges, the isotherms were linear, suggesting conformity of the phosphate adsorption data within these restricted concentration ranges
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East African Agricultural And Forestry Journal, 57 (no1), p. 1-14