<Article>Paddy Soils in Tropical Asia : Part 2. Description of Material Characteristics

Abstract

The material characteristics of 410 sample soils from tropical Asian countries have been described in terms of texture, clay mineralogy, and total chemical composition. Paddy soils of Indonesia, Malaysia, and the Philippines are generally heavy-textured, while those of Sri Lanka are sandy and poor in silt. Bangladesh soils are characterized by a high content of silt. Soils from Burma, Cambodia, India, and Thailand are more heterogeneous with respect to textural composition. There seems to be a general parallelism between clay mineral composition and total chemical composition and in terms of these two material characteristics the following three groups may be set up : 7Å mineral dominant, high silica and low bases-Cambodia, Malaysia, Sri Lanka and Thailand, 14Å mineral dominant, low silica and high bases-Indonesia and the Philippines, 7-10-14Å minerals evenly contained, medium chemical composition-Bangladesh, Burma, and India. As the material characteristics are correlated with each other, separate discussions on individual items seem to be insufficient. In one of the papers to follow we will deal with these material characteristics collectively in order to set up a system for classification of paddy soil materials in tropical Asia.