Shrinkage Characteristics of Soils under Varying Geological Formations in a Humid Tropical Environment of Southeastern Nigeria

Abstract

This study evaluated the shrinkage characteristics and shrink–swell susceptibility of soils developed from different geological parent materials in a humid tropical environment of southeastern Nigeria. Soil samples were collected from three parent materials: Coastal Plain Sand at Eziobodo, Imo Clay Shale at Amuro, and False Bedded Sandstone at Uturu. Samples were obtained from two depths, 0–30 cm and 30–60 cm, with four replicates per depth, giving a total of 24 soil samples. The samples were analysed for selected physical, chemical, and shrinkage-related properties, including particle size distribution, volumetric moisture content, bulk density, soil pH, soil organic matter, effective cation exchange capacity, liquid limit, plastic limit, plasticity index, coefficient of linear extensibility, volumetric shrinkage, and clay activity. Data were subjected to analysis of variance, and treatment means were separated using the least significant difference test at the 5% probability level. The results showed clear differences in soil properties among the parent materials. Coastal Plain Sand soils had the highest sand content of 853 g kg⁻¹, while False Bedded Sandstone soils recorded the highest silt and clay contents of 602 g kg⁻¹ and 260 g kg⁻¹, respectively. Volumetric moisture content ranged from 88.40 to 342.61 g kg⁻¹, while bulk density ranged from 1.51 to 1.66 g cm⁻³. Shrinkage indices were higher in soils derived from False Bedded Sandstone and Imo Clay Shale than in Coastal Plain Sand soils. False Bedded Sandstone recorded the highest liquid limit, plasticity index, coefficient of linear extensibility, and volumetric shrinkage values, while Coastal Plain Sand showed little or no measurable shrinkage response. The findings indicate that geological parent material strongly influences soil shrinkage behaviour in the study area.