Nature of Acid Soils of Sundarbans Delta and Suitability of Classifying Them as Acid Sulphate or Potential Acid Sulphate Soils

The high acidity in some saline soils of Sundarbans delta was due to oxidation of pyrites or sulphidic materials accumulqted in soil in the past when these soils were under tidal mangrove vegetation. Small amounts of oxidizable sulphidic materials still exist in subhorizons of many soils, but these acidic soils could not be classified as acid sulphate soils according to Soil Survey Staff (1975) nor as potential acid sulphate soils. However, using broader terminologies of Dent (1986) rather-than of Soil Survey Staff(l975) some of those soils (occupying about 4 per cent of the study area of about 43000 ha) could be classified as acid sulphate soils. The present state of drainage condition in many of these soils was not favourable for existence of potential acid sulphate soils.