Nature of Acidity in Soils of West Bengal

Eighteen acid soils of West Bengal representing Inceptisol, Alfisol and Entisol order s were studied to characterize their nature of acidity in relation to physicochemical properties. Total potential acidity, total acidity, pH-dependent acidity, hydrolytic acidity and exchange acidity ranged from 1.50 to 11.25, 0.93 to 4.75, 1.41 to 10.35, 0.89 to 3.85, and 0.04 to 1.03 cmol (p⁺ kg⁻¹, respectively. Excepting hydrolytic acidity, all other forms of acidity were highest in Inceptisols followed by Entisols and Alfisols. pH-dependent and hydrolytic acidities contributed 86.9 to 99.2 and 77.4 to 97.6 per cent of the total potential acidity and tota! acidity, respectively, with little (0.8 to 22.6%) contribution of exchange acidity. The contribution of electrostatically bound hydrogen to exchange acidity was highest for Entisols (58.1%) followed by Alfisols (43.6%) and Inceptisols (34.1%); opposite was true for electrostatically bound aluminium. All these ferms of acidity showed significant positive correlations with organic C and forms of Al in soils but negative correlations with soil pH. They also showed significant correlations with each other. Among the soil properties, pH, organic C and exchangeable Al caused most of the variations in different forms of soil acidity.