Studies on the Tungabhadra Catchment Soils I. Environmental Characteristics and Soil Morphology

Red, black and alluvial soils constitute the major soil groups of the Tungabhadra catchment area. A genetic study of nine soil profiles, three each pertaining to each one of the above mentioned groups and taxonomically representing established soil series reveal that they owe their origin to widely varying geologic parent materials, associated with micro-climatic changes conditioned by topographic variations of low magnitude. The two non-black alluvial soils usually occupied low physiographic positions and the presence of pyroxene and amphibole in them revealed that they have undergone less severe weathering. The presence of orthoclase and plagioclase feldspars indicated their mixed parentage with a predominantly gneissic makeup. The black soils occupied mid-land situations and the preponderance of plagioclase feldspar reflected their origin from base rich schistic rocks. The red soils occupied higher physiographic positions and except one soil of colluvial origin, have developed from granite-gneiss rock, and have undergone prolonged weathering as evidenced by the presence of resistant minerals like garnet aud zircon in significant amounts. The climatic conditions favoured almost negligible amount of illuviation to take place.