Soil texture and lithological discontinuity mapping for sustainable land use planning: An application of digital soil mapping in a part of Eastern Himalayan Foothills, India

Abstract

Soil texture and lithological discontinuity (LD) mapping, when integrated with digital soil mapping (DSM) techniques, provides a critical framework for understanding soil variability and its impact on land suitability, offering valuable insights for informed and sustainable land use planning. The present study aimed to produce spatial variability map of particle size content-based soil texture classes and LD in a part of fragile Himalayan foothills of Jalpaiguri district, India at 30 m resolution upto 200 cm depth. Total 470-soil profile samples were collected from 141 geo-referenced sites based on cLHS model. The Equal-area Quadratic Spline method was implemented for soil depth harmonization prior to applying Quantile Regression Forest (QRF) algorithm to predict soil particle size contents at six standard depths, as per Global Soil Map standards. The 141-datasets were divided into calibration and validation sets to evaluate model performance. Additionally, the Uniformity value index was employed to characterize LD in the region. The study revealed notable variability in soil texture across depth intervals, with clay content gradually decreasing with depth. Satellite imagery, terrain, and climate variables were important in predicting surface clay content, whereas only climate and terrain variables influenced clay distribution down the profile. The predicted textural classes indicated loam and sandy loam in northern elevated foothills and silt loam across southern flat surface, favouring tea cultivation in the north, while rice, jute, and potato in southern areas. A widespread LD was found at 60–100 cm depth, stemming from gravity-driven colluvial material deposition from higher slopes of Himalaya, surface erosion–deposition processes, and neo-tectonic activity. The higher accuracy of predicted soil particle size contents and LD maps demonstrated capability of QRF model. These insights into soil texture and LD driven site-specific land use decisions, crop selections, and management practices in colluvial soils of similar physiographical setup might promote the operational applicability of DSM studies globally.