Physicochemical Characterization of Agricultural Soils under Chlorpyrifos Contamination

Abstract The intensification of agricultural activities in the Lower Niger River Basin, Ilorin, Nigeria, has led to repeated applications of chlorpyrifos, raising concerns regarding its effect on soil physicochemical properties. This study investigated the influence of chlorpyrifos contamination on pH, temperature, moisture content, water holding capacity, organic matter, and soil texture in agricultural soils. Guided by environmental chemistry principles governing pesticide–soil interactions, the research employed a quantitative, cross-sectional design. Soil samples were systematically and purposively collected from three farms, with composite samples taken at 0–15 cm depth. Physicochemical analyses were conducted using precision-calibrated instruments, validated through triplicate measurements, and data analysed via descriptive statistics and one-way ANOVA with post hoc Tukey’s HSD tests at α = 0.05, with effect size (η²) also calculated to quantify the proportion of variance attributable to site differences. Results revealed significant differences (p < 0.001) and extremely large effect sizes for soil pH and water holding capacity across sites, while temperature, moisture content, and organic matter showed no significant differences (p > 0.05) despite medium to large effect sizes. Soils were predominantly sandy, with low moisture retention and organic content, suggesting limited fertility and vulnerability to environmental stress. The findings suggest potential associations between pesticide exposure and changes in selected soil physicochemical parameters. It is recommended that integrated soil remediation and monitoring strategies be adopted to mitigate pesticide-induced soil degradation in the region.