Integrated Spatial Evaluation of Soil Quality Using Analytic Hierarchy Process (AHP) –Weighted Sum Method (WSM) Modelling and Multivariate Statistical Analysis

Soil degradation is a major constraint to ecosystem sustainability and agricultural productivity, particularly in erosion-prone mountainous microcatchments where spatial heterogeneity complicates soil management. This study presents an integrated spatial framework for assessing soil quality in the Çapakçur Microcatchment (Eastern Türkiye) by combining geostatistical interpolation with multi-criteria decision analysis. Eighteen soil indicators representing physical, chemical, and nutrient properties were spatially modelled through Inverse Distance Weighting (IDW) and weighted using the Analytic Hierarchy Process (AHP). The Weighted Sum Method (WSM) was then applied to derive a composite Soil Quality Index (SQI) that integrates multidimensional soil attributes into a single decision-support layer. Results indicate that physical attributes exert the greatest influence on overall soil quality, while chemical and nutrient parameters display strong local variability. Approximately 85% of the study area falls within moderate-to-low soil quality classes, highlighting widespread fertility limitations associated with organic matter depletion, phosphorus fixation, and salinity. Principal Component Analysis (PCA) confirmed the statistical robustness of the AHP–WSM weighting, explaining 84.1% of the total variance, while Spearman correlation analysis revealed that elevation and erosion intensity are key determinants of soil functionality (rₛ = 0.67 and − 0.61, respectively). The proposed AHP–WSM–GIS framework provides a reproducible model for identifying soil degradation hotspots, prioritizing rehabilitation zones, and guiding precision land management strategies in heterogeneous mountain ecosystems. Beyond its regional application, the methodology contributes a transferable decision-support tool for sustainable land use and the achievement of global soil-related Sustainable Development Goals (SDG 13 and SDG 15).