A Multi-Indicator Assessment of Soil Degradation Under Contrasting Land Use Systems in Coastal Plain Sands of Imo State Southeastern Nigeria

Soil degradation remains a major constraint to sustainable land management in tropical ecosystems, particularly in regions undergoing rapid land use transformation. This study applied a multi-indicator approach to evaluate soil degradation under four contrasting land use systems—oil palm plantation, secondary forest, industrial layout, and residential areas—within the Coastal Plain Sands of Imo State, Southeastern Nigeria. Eight profile pits were excavated, and thirty-seven soil samples were collected across genetic horizons for the analysis of selected physicochemical properties and degradation indices, including dispersion ratio (DR), clay dispersion ratio (CDR), clay flocculation index (CFI), clay dispersion index (CDI), structural stability index (S), exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR).Results revealed significant variation in soil quality across land uses. Industrial and residential soils exhibited higher bulk density (1.64–1.73 Mg m⁻³), lower total porosity (35.16–38.16%), and reduced soil organic carbon (0.34–0.54 g kg⁻¹) compared to secondary forest soils. Dispersion indices were consistently above critical thresholds (DR: 0.46–0.85), indicating widespread susceptibility to structural breakdown, while structural stability values remained very low (S: 0.22–0.72), reflecting severe physical degradation. In contrast, secondary forest soils showed relatively improved aggregation and soil condition. Although ESP (2.11–4.33%) and SAR (0.11–0.24) were below sodicity thresholds, elevated dispersion and low structural stability indicate increasing vulnerability to degradation.In conclusion, soil degradation followed the gradient: secondary forest < oil palm plantation < residential layout < industrial layout. The findings demonstrate that degradation is primarily driven by compaction and organic matter depletion rather than sodicity. The multi-indicator framework proved effective in capturing the complexity of soil degradation and provides a robust basis for sustainable soil management in fragile tropical soils.