Studies on the Contribution of Fertilizers to Heavy Metal Levels in Soils and Cocoa from some Cocoa Farms in the Western Region of Ghana

摘要

Continuous applications of fertilizers to soils are known to increase heavy metal concentrations to levels that may eventually exceed natural levels in soils. In this study, the levels of heavy metals comprising, Cu, Pb, Mn, Zn, Ni, Cd, Cr, and Fe in five major fertilizers namely, Cocoa Asaasewura; Sidalco Balanced; Sidalco Potassium Rich; Cocofeed; and Nitrabor usually supplied by Ghana Cocoa Board (COCOBOD) to cocoa farmers, were determined. In order to assess the possible contributions of these fertilizers to the background levels in the soil and cocoa beans, the levels of the heavy metals were also determined in farm soils and cocoa bean samples from farms that have been fertilized for at least three years. Results from the analyses indicated that in general, Sidalco Balanced and Sidalco Potassium Rich had relatively very high levels of Mn, Cu and Zn but low levels of Pb, Ni and Cd. Cocofeed and Asaase-wura also had very high levels of Fe, Ni, Pb and Cd. Nitrabor generally had the least levels for almost all the metals. Fe occurred as the highest metal in all cases while Zn was the least recorded metal in the fertilizers. In general, contributions from the fertilizers to the metal levels in the soil and in the cocoa beans have been found to be minimal and fall within acceptable limits in the cocoa beans. .