Characterization and classification of soils in the Bettadapura micro-watershed of lower Tungabhadra catchment using a geospatial approach

Abstract

Detailed soil resource information is crucial for effective land use planning, especially at the micro-watershed level. This study aimed to characterize and classify the soils of the Bettadapura micro-watershed (690.69 ha), part of the Harisamudra sub-watershed in Kadur taluk, Chikkamagaluru district, Karnataka, India, using field studies and geospatial techniques. Soil profiles were examined along transects, and seven representative master pedons were selected from detailed morphological, physico-chemical analysis. Soils were classified according to USDA Soil Taxonomy. Geospatial tools (Remote Sensing and GIS) were employed using high-resolution QuickBird satellite imagery and cadastral maps (1:7920 scale) as a base for mapping soil variations. Morphological studies revealed soil depths ranging from moderately shallow (50-75 cm) to very deep (>150 cm). Soil colours varied from dark red (2.5YR 3/4) to reddish yellow (10YR 6/6). Soil texture varied from sandy loam in surface horizons to sandy clay or clay in subsurface horizons, exhibiting subangular blocky structure. Physico-chemical analysis indicated slightly acidic to moderately alkaline reaction (pH 6.17-8.51), non-saline nature (EC 0.05-0.44 dS m-1), low to high soil organic carbon (3.6-9.6 g kg-1), and variable calcium carbonate content (4.00-12.50%). Cation exchange capacity ranged from 8.40 to 30.85 cmol (p+) kg-1, generally increasing with clay content and depth. The soils were classified under two orders: Inceptisols (Typic Haplustepts - Loamy, isohyperthermic; Chikkathur series) and Alfisols (Typic Haplustalfs - Fine, isohyperthermic or Clayey-skeletal, isohyperthermic; Vittalapura, Duglapura, Gijikatte, Sappinahalli, Madhugundi, and Giriyapura series). A total of 33 soil phases were delineated and mapped, providing a detailed soil resource inventory crucial for site-specific management and sustainable land use planning in the watershed.