Linking soil taxonomic characterization with GIS–AHP modelling for groundnut land suitability assessment in southern India

Groundnut cultivation in seasonally dry tropical landscapes is strongly influenced by soil heterogeneity, landscape position and management constraints, requiring crop-specific land evaluation for sustainable production. In this study, detailed field pedology and USDA Soil Taxonomy were used to characterize and interpret soil variability, while GIS–Analytical Hierarchy Process (GIS–AHP) modelling was used separately to weight and combine crop-suitability criteria for the Puttur division of Tirupati district, Andhra Pradesh, India. Twenty representative pedons spanning major geomorphic positions were described and 85 horizon-wise samples were analysed. The soils were classified as Alfisols, Inceptisols and Entisols under ustic moisture and isohyperthermic temperature regimes. The AHP matrix assigned the greatest weights to drainage (21.03%), exchangeable Ca (16.08%), texture (15.88%) and effective rooting depth (11.76%); λmax = 11.3782, CI = 0.0378 and CR = 0.0250 indicated acceptable internal consistency of the pairwise judgements. Suitability patterns were governed mainly by drainage, Ca status, texture, rooting depth and slope, with low organic carbon and suboptimal soil reaction acting as additional local constraints. Soil Taxonomy was not used as an AHP criterion; rather, taxonomic and pedogenic information was used to interpret why constraints differed among pedons. The GIS–AHP output is therefore presented as a relative spatial screening framework, and independent yield validation is identified as a requirement for further model testing.