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• <br />• <br />I• <br />Nickel. This is anon-essential (to plant and animal life) heavy metal that could induce plant toxicity <br />symptoms if present in excess quantities. Nickel toxicity problems are restricted to poorly drained, <br />very acid soils, soils derived from serpentine parent materials or soils that have been contaminated <br />near smelters (Traynor, 1980; Munshower, 1983; and Barth et al., 1981). Normal plant available <br />nickel concentrations in soil are slightly less than 2 ppm (Barth et al., 1981). <br />Zinc. Zinc is a necessary component of several enryme systems which regulate various metabolic <br />activities within plants. Adequate zinc levels are essential for normal cell division, root growth, seed <br />production, protein metabolism, and auxin formation (Tiedemann and Lopez, 1982). For normal <br />growth, most plants generally require a minimum zinc concentration of 1 ppm while zinc related <br />toxicity occurs at about 70 ppm. The potential for zinc deficiency is increased by many factors <br />including but not limited to high pH, high lime rates, high phosphorous levels, and high <br />concentrations of other metallic nutrients (Cu, Fe, and Mn). Zinc toxicity is more of a concern on <br />acid soils because of the higher solubility of zinc on acid soils. The antidote for zinc toxicity is the <br />application of lime (Traynor, 1980). <br />Cadmium. Cadmium is anon-essential metallic element that is used in industry. Plant toxicities <br />due to elevated levels of cadmium under natural conditions or in reclamation are unlikely (Barth et <br />al., 1981 and Munshower, 1983). <br />Mercury. Mercury predominantly exists in an inorganic form which is not absorbed readily by <br />plants. There have been no documented cases of mercury toxicity to plants or to animals under <br />normal conditions. Mercury toxicity is limited to industrial or agricultural situations where mercuric <br />fungicides or other contaminants are used. <br />Lead. This is anon-essential (to plant and animal life) heavy metal that could induce plant toxicity <br />symptoms if present in excess quantities. As the pH decreases, the solubility and the potential for <br />lead toxicity increases. Inmost soils of the Great Plains, lead is complexed and not readily leached <br />to ground water nor available for plant uptake (Barth et al., 1981 and Munshower, 1983). <br />Arsenic. Munshower (1983) states that toxic concentrations of arsenic in natural soils and <br />overburden have never been reported. Barrett and others (1980) stipulate that toxicity is confined <br />REVISED Auguat 2006 2.4.6-23 <br />