Morphology and Characteristics of Some Acid Sulphate Soils in Kerala State

Acid sulphate soils, confined to the Malabar coast in south-western part of India, have developed under humid and tropical climate on the alluvium derived mainly from laterite and lateritic soils and occupy lagoons and similar lowlying geomorphic situations. The soils are generally rich in organic matter. Prolonged submergence from May to December due to heavy discharge from numerous rivers and streams is followed by sea water inundation during the subsequent lean months as a result of tidal cycles.

A great deal of heterogeneity exists with regard to soil characteristics such as colour of soil matrix and mottles (indicating varying degrees of gleying, reduction and bleaching), salt concentration (ECe ranging from 2.9 to 44.4 and 1.5 to 74.6 mmhos/cm in the epipedon and substratum, respectively), pH (3.4 to 7.5) and organic matter content (0.5 to 40.5%). Differences observed with regard to acidity can be mainly ascribed to the heterogeneity in the distribution of pyritous clays in the alluvium. Soil reaction, organic matter status and associated factors facilitate their classification as Tropaquents (saline slightly acid, pedon I), Sulfohemists (saline acid sulphate, pedon II), Hemistic Aquents (saline neutral, pedon III) and Sulfoaquents (non-saline acid soil, pedon IV).