The E4/E6 value of humic substance of Entisol, Alfisol and Vertisol was less than 5.0, but it was highest for Vertisol. The acidity of humic substance of Entisol obtained by potentiometric titration was more than the humic substances of Alfisol and Vertisol. The nature of complexation of HA (Humic acid) substance, with soil Ca-clay showed that the ability of the humic substances to complex soil varied in the order: Alfisol < Vertisol < Entisol. The infrared bands of HA-substances of the three different soils were somewhat distinguishable.
Humic acid, Entisol, Alflsol and Vertisol, E4/E6 ratio, exchangeable acidity, IR-study, the soil-Ca-clay
