Effects of Long-Term Cultivation on Soil Physicochemical Properties and Heavy Metal Accumulation

Abstract

This study evaluated the effects of long-term cultivation on the physicochemical properties of soil, including pH, organic matter (OM), electrical conductivity (EC), cation exchange capacity (CEC), and concentrations of some heavy metals (HMs) such as Cr, Cu, Cd, Mn, Zn, Ni, Fe, and Pb of Open Farm (OF) soils. A total of 210 soil samples were collected from six depths (0-60 cm). The findings revealed slight alterations in physicochemical properties resulting from cultivation and chemical fertilizers. Heavy metal concentrations in OF soils were below maximum permissible limits, but Cu, Cd, Mn, and Zn accumulated compared to uncultivated soils. The heavy metals pollution index (HPI) indicated low pollution for Fe in OF soils (PI ≤ 1), with HPI values decreasing with increasing soil depth. The Geoaccumulation index (Igeo) indicated that Open-farm soils were uncontaminated or moderately contaminated with Mn. A strong positive correlation between physicochemical characteristics and heavy metals in OF soils suggests a common pollution source, whereas negative correlations indicate different pollution sources. Principal component analysis (PCA) identified three major components in soil, each associated with specific heavy metals. The study indicated that Cd, Cu, and Zn originated from agricultural activities, while Cr, Ni, Fe, and Mn were derived from natural soil-forming processes.