Effects of Cadmium, Copper and Zinc Interactions in Soil on their Phytoavailability in Pumpkin (Cucurbita moschata)

Experiments were conducted on pumpkin planted and grown in pots under glasshouse conditions to study the interactions between cadmium, copper, and zinc in soil and the effects on their uptake by pumpkin. Known amounts of Cd, Cu and Zn were added to the soil both in single and combined forms before planting, and the possible synergistic or antagonistic interactive effects viz-a-viz their uptake by pumpkin evaluated. The concentrations of the heavy metals both in soil and pumpkins leaves were determined using atomic absorption spectrophotometer (AAS). The results showed various types of interactions among the metals. Generally, it was observed that the addition of Cd to the soil lowers the concentrations of Cu and Zn, while the application of Cu to the soil raises the concentration of Cd and lowers the concentration of Zn. On the other hand, the application of Zn to the soil led to an increase in the concentration of Cd and a decrease in the concentration of Cu.  Cu suffers more antagonistic effects in the presence of Cd and Zn. The Transfer Factors for the treated soils were generally lower than that of the untreated soils, this implies that high concentrations of one metal could lower the uptake of another. The generally high Transfer Factor revealed that pumpkin leaves have the ability to accumulate the metals. This calls for concern especially in the case of Cd, which is highly toxic and of no known biochemical importance. Keywords: cadmium, copper, zinc, interactions, uptake, pumpkin