Abstract
The effect of copper and zinc, at concentrations of 200 and 2000 mu g/g, on soil microbial populations and on the activities of three soil enzymes was investigated. Both clay and sandy soils were used, and results are presented in terms of the effects on glucophilic fungi, cellulose-decomposing fungi, thermophilic and thermotolerant fungi, bacteria, and actinomycetes. Overall, both doses of each heavy metal in either soil type caused a noticeable decrease in counts of soil microorganisms. Urease activity was affected most by both metals, with significant and complete inhibition at the low and high concentrations, respectively. A similar effect was observed for nitrate reductase activity, but to a lesser extent, while amidase activity was only marginally inhibited.