Effect of Organic Amendments on the Adsorption and Desorption of Sulphate Sulphur in a Typic Ustochrept Soil

The effect of continuous application of organic manures to soils on the adsorption and desorption of sulphate-sulphur was studied in a Typic Ustochrept soil. Soil samples were collected from permanent research experiment where FYM and Sesbania green manure have been applied continuously as treatment to every kharif crop. The amount of sulphate adsorbed by the soil in the presence and absence of organic manures increased with the rise in sulphate concentration in equilibrium solution, the magnitude of increase varied between the treatments. The organic amendments appreciably increased the adsorption of added sulphate and the increase was higher in Sesbania green manure than farmyard manure treatments. Sulphate adsorption conformed very well to Freundlich and Langmuir adsorption isotherms as well as extended Freundlich and Temkin equations. More than 90% of adsorbed sulphate was desorbed with 0.15% CaCI₂.