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zinc concentration of 1 ppm while zinc related toxicity occurs et about 70 ppm. The potential for zinc <br />deficiency is increased by many factors including but not limitetl to high pH, high lime rates, high <br />phosphorous levels, and high concentrations of other metallic nutrients ICu, Fe, and Mn). Zinc toxicity is <br />more of a concern on acid soils because of the higher solubility of zinc on acid soils. The antidote for <br />zinc toxicity is the application of lime (Traynor, 19801. <br />Cadmium. Cadmium is anon-essential metallic element that is used in industry. Plant toxicities due to <br />elevated levels of cadmium under natural conditions or in reclamation are unlikely (Barth et al., 1981 and <br />Munshower, 19831. <br />Mercury. Mercury predominantly exists in an inorganic form which is not absorbed readily by plants. <br />There have been no documented cases of mercury toxicity to plants or to animals under normal <br />conditions. Mercury toxicity is limited to industrial or agricultural situations where mercuric fungicides or <br />other contaminants are used (Barth et al., 1981 and Munshower, 19831. <br />Lead. This is a non-essential Ito 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 lead <br />toxicity increases. In most soils of the Great Plains, lead is complexed and not readily leached to <br />ground water nor available for plant uptake (Barth et al., 1981 and Munshower, 19831. <br />• Arsenic. Munshower (19831 states that toxic concentrations of arsenic in natural soils and overburden <br />have never been reported. Barrett and others (19801 stipulate that toxicity is confined to soils which <br />have accumulated arsenic through foliar spray compounds. The arsenates are fixed by soils in a relatively <br />insoluble state and are not lost by leaching. The critical water-soluble arsenic concentration in soils is 2 <br />ppm (USDA, 19571. <br />Aluminum. Aluminum is anon-essential metallic element that could induce plant toxicity symptoms if <br />present in excess quantities. Although aluminum is the third most abundant element in the earth's crust, <br />it is typically available for plant uptake in only trace amounts in alkaline soil (Traynor, 19801. Like other <br />heavy metals, the aluminum concentration in the soil solution increases as the soil becomes more acid. In <br />extremely <br />• <br />15 Revised 9198 <br />