Physicochemical Properties and Metal Contents of Soils of Selected Farmlands in Oromia Regional State, Ethiopia: Implications to Soil Management

Abstract

In this study, the physicochemical properties and the constituents of selected metallic substances from the farmland soils that were collected from four agricultural sites; namely, Boji, Gedo, Hirna and Kubsa Kidame of the Oromia Regional State of Ethiopia, have been investigated.  The surface soil samples, collected from 0-20 cm depth and from identical slopes at each site, were pretreated following the standard methods to obtain composite samples. The selected physicochemical properties of the processed samples; specifically, moisture contents, pH, organic matter, electrical conductivity and soil texture, were also analyzed following the standard procedure. For determination of the metal contents, soil samples were digested and analyzed using Flame Atomic Absorption Spectrometry. The analyzed soil samples were found to contain organic matter of 3.24 to 3.96 (medium class); electrical conductivity in the range of 0.13 to 0.21 mScm^-1, indicating that the soil samples are not salt-affected;  pH in the range of slightly acidic to neutral (5.75–6.94); and textural class dominated by clay, constituting 41.4–56.2%. Variations in the metal concentrations (mg kg^-1) were: Calcium (9330–18900), Cadmium (3.88–4.45), Chromium (30.7–99.5), Cupper (12.6–42.3), Iron (654–875), Manganese (133–255), Lead (14.9–30.2), and Zinc (217–289). Based on percent recovery, the accuracy of the results were within the acceptable range of 91.2–103 %. The experimental results fairly suggests that the farmland soils could safely be utilized for cultivating different agricultural products. There are possibilities of further extending the works at other farmlands.