INNOVATIVE MODELLING OF SOIL PHYSICOCHEMICAL PROPERTIES FOR PREDICTING HYDRAULIC CONDUCTIVITY IN ABIA STATE

Abstract

Understanding the relationship between soil physicochemical properties and water movement is essential for optimizing agricultural productivity, resource management, and environmental sustainability. This study models the physicochemical properties and hydraulic conductivity (K) of soils in Abia State, Nigeria, using Response Surface Methodology (RSM). Focusing on three senatorial districts: Abia North, Abia Central, and Abia South; the research examines how soil texture, physical structure, and chemical composition influence hydraulic conductivity at varying depths (1-15 cm, 16-25 cm, and 26-35 cm). The study covers different soil types, including Ferralitic, Hydromorphic, and Alluvial soils, with a focus on improving irrigation, fertilizer application, and erosion control. Field sampling was conducted systematically across selected agricultural zones, resulting in 27 composite soil samples. These samples were analyzed for physical properties such as sand, silt, clay, bulk density, porosity, particle density, and hydraulic conductivity. Chemical properties examined included nitrogen (N₂), organic carbon (OC), calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), and phosphorus (P). Laboratory analyses adhered to standardized methods, and data were processed using RSM to understand variable interactions and predict hydraulic conductivity. The results revealed significant spatial and vertical variations in soil characteristics. Sand was dominant in the topsoil, averaging 61.24%, while clay content increased with depth, particularly in Ferralitic soils of Abia South. Silt content remained relatively constant. Bulk density increased with depth, ranging from 1.12 to 1.82 g/cm³, while porosity decreased, indicating soil compaction. The models demonstrated high predictive accuracy (R²>0.85), confirming that soil texture, structure, and organic content significantly influence hydraulic conductivity. High organic carbon improved K in sandy soils but was less effective in clay-rich layers unless supplemented by calcium or porosity.