Abstract

Vernonia amygdalina Del was grown in soil treated with a mixture of cadmium and zinc in different concentrations (25, 50, 75 and 100 mg/kg) to investigate the effect of the treatments on the growth of V. amygdalina. Identical stem cuttings were collected and sown in buckets filled with 5 kg dry soil. These were allowed to grow for a month before the soil samples were treated with the mixture of metals. The experiment included control and four concentrations in three replicates. Data were collected monthly for 12 months. Results on plant height, number of leaves, number of branches and girth showed adverse effect of treatment unlike leaf area which was enhanced. There was significant difference between height values recorded for control and the various treatments – the heights for control, the 25 mg/kg, 50 mg/kg, 75 mg/kg and the 100 mg/ kg treatments at 12 MAT were 77.43±1.03, 59.23±2.80, 55.83±1.57, 35.13± 0.86 and 31.47±2.08 cm respectively. There was decreased soil pH, microbial load and nutrients. There was however an increase in soil carbon. The presence of zinc reduced the uptake of cadmium in the plant. The increased presence of heavy metals affected the cell division process of the plant, lowered the soil pH – causing an increase in bioavailable heavy metals for uptake, decreased the available nutrients for plant growth due to competition and disrupted the soil’s natural microbial flora. Though the accumulation of heavy metals in the plant were below tolerable limits, prolonged consumption may result in poisoning.

Key Words: Mixture, Treatment, Cadmium, Zinc, Vernonia amygdalina

DOI: https://ejesm.org/doi/v12i3.6