Forms and Distribution of Soil Acidity in at Surface and Sub-surface Soils under Different Landforms and Land Uses, Tropical Humid Region, India

Background: In soils of the humid tropics, acidity is a major natural threat. To know the forms and distribution of soil acidity on surface and sub-surface soil depths in different landforms and land uses, a study was conducted in the Elamdesam block, Idukki district, Kerala. Methods: Soil samples from 28 profiles across various landforms and land uses were analysed for water extractable acidity, KCl extractable H and Al and BaCl2 acidity. Six profiles from uplands and lowlands from different land uses were taken and aluminium saturation was determined. Result: Soils are extremely acidic to moderately and strongly acidic. KCl exchangeable H ranged from 0.17 to 2.45 at the surface and up to 3.19 meq/100 g in the subsoil. KCl exchangeable Al ranged from 0.22 to 0.96 at the surface and up to 1.73 meq/100 g in the subsoil. BaCl2 acidity ranged from 1.65 to 23.27 at the surface and up to 26.60 meq/100 g in the subsoil. KCl exchangeable (H+Al) ranged from 0.66 to 2.89 at the surface and 0.07 to 3.55 meq/100 g in the subsoil. Al saturation ranged from 13.80 to 43.52 at the surface and up to 70.92 per cent in the subsoil. Soils of uplands had more exch. H, exch. Al, exch. (H+Al) and BaCl2 acidity than lowlands. Among land uses, rubber plantation has more exch. H, exch. Al, exch. (H+Al) and BaCl2 acidity and aluminium saturation. To ameliorate soil acidity effectively, the application of burnt lime to the soil surface and gypsum to the subsoil has been recommended as part of sustainable land management practice.