Impact of soil quality on elemental uptake by, and distribution in, Colocasia esculenta (Amadumbe), an edible root

Abstract

In this study the elemental distribution of selected essential (Ca, Mg, Al, Mn, Cu, Fe, Co, Cr, Zn, Ni and Se) and the non-essential (Pb, Hg and As) elements were determined in the bulb and peel of Amadumbe (Colocasia esculenta) samples from eight different sites in KwaZulu-Natal, South Africa. The concentration of Se and As in the soil and in the Amadumbe bulbs were below the detection limit of 0.09 μg g⁻¹. The total and bioavailable concentrations of the elements in conjunction with pH, soil organic matter (SOM) and cation exchange capacity (CEC) were determined in the soil samples from the eight sites. Statistical analysis was done to evaluate the impact of soil quality parameters on the chemical composition of the Amadumbe root. The results show accumulation or exclusion of certain elements by the bulb as evidenced by the noticeable increase or decrease of the concentrations of elements, respectively. Ca and Mg were found to be major elements in the range (2000–12000 μg g⁻¹), whilst Mn, Zn, Fe and Al were found to be minor elements in the range (20–400 μg g⁻¹). A general trend observed was that the plant favours the absorption of Zn over Cu. A positive correlation between Mg & Ca, Cu & Fe and Co & Ni was also observed. Statistical analysis revealed that the plant tended to accumulate Mg, Ca, Co, Cr and Pb whilst it excluded Hg and Fe, to a lesser extent.

Keywords:

• Colocasia esculenta
• Amadumbe
• cocoyam
• taro
• elemental distribution
• Zn and Cu accumulation
• Hg exclusion
• bioavailability
• nutrient uptake

Acknowledgments

Authors thank the technical team in the School of Chemistry at UKZN (Westville) for their assistance. Ms. Reddy acknowledges the help she received from R. Govender, J. Govender, N. Madlala, G. Reddy, S. Lushaba, Mr. Jagannath, D. Ramsamy and M. Moodley in collecting the Amadumbe and soil samples from the different KZN locations.