Influence of inorganic fertilizers and cattle manure on copper solubility and uptake by Phaseolus vulgaris

Abstract

Long term use of Cu-based fungicides has considerably polluted soils under coffee plantations in Kilimanjaro, Tanzania. High concentrations of copper in soils may lead to enhanced uptake by plants and contaminate the food web. This study explores the effects of inorganic fertilizers, cattle manure and their interaction effects on Cu availability to bean (Phaseolus vulgaris) grown on Cu contaminated soils with the purpose of assessing risks of contamination of the food web associated with growing bean plants on such soils. A pot experiment was carried out in a glass house using long-term Cu contaminated soils collected from Moshi Rural and Mwanga districts in Kilimanjaro, Tanzania. Air dried cattle manure was applied at two rates and applied both with and without inorganic fertilization. Cattle manure significantly increased soil pH, EC and water extractable organic carbon (WEOC) in both soil types. Fifteen percent of cattle manure application rate in Moshi soils decreased the Ethylenediaminetetraacetic acid (EDTA)-extractable Cu. The highest concentration of Cu in bean shoots was observed in the soils treated with inorganic fertilizers but without cattle manure in Moshi soils. Cattle manure in Moshi soils reduced the concentrations of Cu in bean. Bean shoots did not take up excessive quantities of Cu and therefore risks of growing beans on the soils studied appear to be low.

Key words: Bioavailability, pH, contamination, food web, soil