Abstract:
Cassava (Manihot esculenta Crantz) and rubber (Hevea brasilienis Muell. Arg.) form the major land uses along the midland region of Kerala where laterite soils predominate. .Thisstudy was conducted to find out the comparative impact of cassava and rubber on soil acidity parameters at Angadippuram in Kerala state, which is considered as the 'type locality' of laterite soils. Pedons were dug to a depth of 2 m from three selected land uses viz., cassava, rubber and uncultivated barren and genetic horizon samples were collected to study various soil acidity parameters. The study showed that all the pedons under study have a negative ApH value indicating a net negative surface charge throughout the profiles. Highest negative ApH value was noted, among surface horizons, in soils under rubber. Amorphous alumino-silicates could be observed in the surface layers of all three pedons as indicated by high pH (NaF) values. The exchange sites and soil solutions were dominated by exchangeable aluminium and the values were very high in textural-B horizons and hard laterite layers. The surface horizon of soils under cassava recorded significantly lower exchangeable Al compared to other two land uses. The base saturation values (sum of cations) for surface horizons were 25.60, 21.57 and 19.14 per cent respectively for pedons under cassava, rubber and uncultivated barren.
