Sulfate Movement, Adsorption, and Desorption in Three Costa Rican Soils
- E. Bornemisza and
- R. Llanos2
The movement, adsorption, and desorption of sulfate was studied, using samples from the A and B horizons of three soils from Costa Rica. Water, equivalent to 509 mm, was applied to small lysimeters and the distribution of radiosulfate in the columns was determined for untreated soils and samples previously incubated with one of the following substances: (NH4)2SO4, K2SO4, simple, or triple superphosphate. Little sulfate movement was observed. This was enhanced slightly by phosphates.
Sulfate adsorption from solutions containing 100 to 1,000 ppm sulfate fit Freundlich isotherms. Very concentration-dependent adsorption was indicated for alluvial soils but little concentration-dependent adsorption was noted for latosols. Sulfate desorption by water depended greatly on soil type but was less variable when phosphate solutions were used as desorbants. Higher phosphate concentration increased desorption but the latosols retained appreciable sulfate amounts even against extraction by a 1,000-ppm phosphate solution. Some hydroxyl displacement on sulfate adsorption occurs as shown by higher pH values for K2SO4, soil suspensions in comparison with soil suspensions in KCl of equal normality.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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