Characterization and Classification of the Soils of Dorika Watershed of Assam using GIS and Remote Sensing Techniques

Abstract

A study was conducted for characterization and classification of the soils of Dorika watershed in Assam. The watershed was delineated into four distinct physiographic units viz., piedmont plain, hill slopes, alluvial plain and recent flood plain based on Survey of India toposheet (1:50,000 scale) in conjunction with Resourcesat- 2, L4 FX data. Out of total 273 km2 geographical area, alluvial plain occupied 193 km2, recent flood plain 44 km2, piedmont plain 31 km2 and hill occupied 4.9 km2 area. In general, the soils varied considerably in morphological, physical and chemical properties. The dominant hue was 10YR, value ranging from 2.5 to 7 and chroma of 1 to 6 in the study area. The soils were found to be strongly acidic in reaction. Sand, silt and clay content ranged from 7.3 to 71.5%, 12.9 to 50.4% and 12.5 to 53.3%, respectively. The organic carbon ranged from 6.1 to 24.0 g kg-1 in surface and 4.6 to 15.6 g kg-1 in subsurface horizon, cation exchange capacity from 4.7 to 11.8 cmol(p+)kg-1 in surface and 4.8 to 12.2 cmol(p+)kg-1 in sub-surface horizon and texture varied from sandy loam to clay throughout the horizons. The soils were low to medium in available N and P and medium to high in available K. Soils were classified as Fluvaquentic Dystrudepts (P1 and P9), Typic Dystrudepts (P2 and P3), Oxiaquic Dystrudepts (P4 and P6), Aquic Dystrudepts (P5 and P7) and Typic Endoaquents (P8) at subgroup level.