Sulfate desorption from representative soils of the Sao Paulo State, Brazil

We determined the sulfate desorption in representative soils of the Sao Paulo State, Brazil, and related it to the soil affinity for sulfate ions as estimated by the parameters k(L) and n(F) of the Langmuir and Freundlich equations, respectively. Although the parameters k(L) and n(F) were well correlated, the nonlinear decay of the sulfate desorption with the increase in the soil affinity by sulfate was better defined when the affinity was estimated by the parameter k(L). Despite this, results of multiple regression linear analyses carried out for both k(L) and n(F) were quite similar and allowed us to verify that sulfate desorption tends to increase in subsurface soil layers as they become less acidic and/or have their phosphate-extractable sulfur contents increased trough successive fertilisations and/or amendments with S-containing products. At the same time, sulfate desorption in these soils tends to be restrained by the advance of weathering.