Contemporary Research Analysis Journal

Hydraulic conductivity (K) is one of the most important hydraulic properties of the soil matrix and often considered as one of the most difficult hydraulic properties to obtain. The study is situated within the broader framework of Agricultural & Bioresources Engineering, a field concerned with optimizing natural resources for sustainable Agriculture using Engineering principles. The research aims to evaluate how soil texture, physical structure, and chemical composition interact across various soil types—Ferralitic, Hydromorphic, and Alluvial and how these interactions influence hydraulic conductivity at different depths (1–15 cm, 16–25 cm, and 26–35 cm). These properties are critical for irrigation planning, fertilizer scheduling, erosion control, and the design of soil-water conservation structures. Field sampling was carried out systematically across selected Agricultural zones in Abia State. A total of 27 composite soil samples were collected and analyzed for both physical properties—sand, silt, clay, bulk density, porosity, particle density, and hydraulic conductivity—and chemical properties—nitrogen (N₂), organic carbon (OC), calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), and phosphorus (P). Laboratory analysis followed standardized protocols, and data were subjected to statistical modeling, using Response Surface Methodology (RSM) to investigate multi-variable interactions and predictive capabilities. The results revealed significant spatial and vertical variability in all soil parameters. Texture analysis showed that sand dominates the topsoil (average 61.24%), while clay increases with depth, particularly in Ferralitic soils of Abia South, where values exceed 38%. Silt content remained relatively consistent but played a secondary role in determining hydraulic behavior. Bulk density ranged from 1.12 to 1.82 g/cm³, increasing with depth, while porosity showed a converse trend, reflecting classical compaction profiles. Particle density was stable (~2.34 g/cm³), suggesting mineral-dominant soils with moderate organic input. Hydraulic conductivity values were highly variable (0.02896–0.8211 cm/s), with higher values in sandy topsoils and reduced permeability in clay-rich subsoils. Alluvial and Hydromorphic soils showed moderate to high K values at surface layers, while Ferralitic subsoils in Abia Central and South recorded significantly lower K, likely due to clay accumulation and poor structure. Chemical properties also demonstrated depth-dependent variation. Organic carbon and nitrogen showed steep gradients, declining from surface to subsoil due to leaching and microbial decomposition. Calcium and magnesium were more stable but still declined with depth. Potassium, being highly mobile, showed the steepest drop, especially in sandy or coarser-textured profiles. Phosphorus levels were generally adequate but immobilized in Ferralitic soils due to fixation by aluminum and iron oxides. Sodium levels remained within acceptable limits, except in some alluvial soils where values approached thresholds that could risk structural dispersion. Response surface models were developed using second-order polynomial equations to predict hydraulic conductivity (K) as a function of texture (sand, clay), bulk density, organic carbon, and cation concentrations (Ca, Mg, Na). By integrating physical and chemical properties into a predictive framework, the study empowers stakeholders—farmers, engineers, agronomists, and policy-makers—with data-driven tools for sustainable land management in Abia State and similar agro-ecological zones. The research highlights not only the variability and complexity of tropical soils but also the opportunity to optimize productivity through informed soil management and bioresource engineering interventions.

Response surface, analysis, physicochemical, properties, hydraulic, conductivity, soil

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