Effect of lime and gypsum application on soil acidity and aluminum toxicity in laterite soils

Abstract:

Soil acidity is defined as the condition where hydrogen and aluminum ions dominate the exchange complex, and it affects roughly 49 million hectares of arable land in India. This research investigated the individual and combined effects of lime (CaCO₃) and gypsum (CaSO₄.2H₂O) on soil pH, exchangeable aluminum, base saturation, and root growth of groundnut in acid laterite soils at Professor Jayashankar Telangana Agricultural University, Hyderabad. Five treatments were tested in a randomised complete block design with four replications during kharif 2022: control, lime at 2 and 4 t/ha, gypsum at 2 t/ha, and lime 2 t/ha combined with gypsum 2 t/ha. After six months, lime at 4 t/ha raised soil pH from 4.82 to 6.31 and reduced exchangeable Al from 3.41 to 0.74 cmol/kg. The combined lime-gypsum treatment raised pH to 5.87, reduced Al to 1.12 cmol/kg, and improved root length by 102% over the control. Gypsum alone had a modest effect on surface pH but reduced subsoil Al more effectively than lime alone. These results suggest that combining lime with gypsum addresses both surface acidity and subsoil aluminum toxicity in laterite soils.