Soils on Different Physiographic Units in Lower Brahmaputra Valley Zone of Assam: I. Characterization and Classification

Soils developed on different physiographic units viz. piedmont plain (P₁), alluvial fan plain (P₂), alluvial plain (P₃), flood plain (P₄) and monadnock (P₅) in the lower Brahmaputra valley zone of Assam were studied for their characterization and classification. The soils of alluvial and flood plains have colour with low chroma which is characteristic of seasonal wetness. Soils developed on piedmont and monadnock were finer in texture as compared to other soils. The amount and depth distribution of clay and sesquioxides indicated that the soils on piedmont plain and monadnock are fairly well developed. The soils were classified as Ruptic-Ultic Dystrochrept (P₁), Aquic Udipsamment (P₂), Umbric Dystrochrept (P₃), Oxyaquic Udifluvent (P₄) and Typic Hapludult (P₅). On the basis of Storie index rating the soils were rated as poor (P₂), fair (P₃, p₄, P₅) and good (P₁) classes.