Impact of soil quality on elemental uptake by Zingiber officinal (ginger rhizome)

The elemental distribution in ginger rhizome and the impact of the soil quality on the elemental uptake by the rhizome were investigated. The focus of the study was on eight elements, i.e. Cu, Zn, Mn, Fe, Ni, Pb, Cr and Mg. Ginger and soil samples from four different farms of KwaZulu-Natal (South Africa) were collected and after microwave digestion, the elemental concentrations were estimated using ICP-OES. The method for the ginger analysis was validated by the analysis of a certified reference material (leaves of Poplar). The accumulation of the elements in the ginger rhizome was investigated as well as the metal-metal interactions that exist based on the total and the bioavailable concentrations of the elements were determined. It was found that the soil quality influences the elemental distribution within the ginger rhizome; however, the plant has the inherent ability to control the amount of each element entering the rhizome. The levels of Cd and As in the soil and ginger samples from all four sites were below the lower detection limits. The ginger 'flesh' tends to accumulate Mn and Mg. A synergistic relationship between Cr and Mn; and an antagonistic relationship between Fe and Cu; and Fe and Cr were noticed. The concentration of none of the elements exceeded the threshold upper intake levels, and thus does not pose toxicity issues.