Some Factors Affecting the Adsorption of Sulfate by Alabama Soils
1954
Ensminger, L. E.
The sulfate content of a number of Alabama Soils was determined by extracting with various solutions. The sulfate extracted was measured turbidimetrically. Some factors affecting the adsorption of sulfate by soils were studied. About the same amount of sulfate was extracted by neutral sodium acetate solution, sodium acetate buffered at pH 4.8, KH₂PO₄ solution containing 100 ppm. phosphorus, and KH₂PO₄ solution containing 500 ppm. phosphorus. However, 0.1 N HCl solution extracted little or no sulfate. The samples contained only small quantities of water-soluble sulfate except where sulfate had been recently applied. The results show that sulfate is retained to a certain extent by most soils. The subsurface layers usually contain more sulfate and are capable of adsorbing more sulfate than the surface layers. The surface layers of most of the light textured soils did not contain sulfate or show a capacity to adsorb sulfate from solution. The capacity of soils to adsorb sulfate is affected by certain soil treatments. Increasing amounts of superphosphate applied to a Cecil sandy clay loam resulted in decreasing amounts of soluble sulfate. The data show that superphosphate decreased the capacity of this soil to adsorb sulfate from a CaSO₄ solution. Liming also resulted in a decrease in the retention of sulfate. The sulfate adsorption capacity of a number of materials was determined in an attempt to show what fractions of soils may be responsible for the retention of sulfate. The data show that dehydrated Al₂O₃ adsorbed much more sulfate than any of the other materials. The iron minerals adsorbed rather small amounts of the sulfate while the Davidson colloid, kaolinite, and bauxite were intermediate.
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