Plant Uptake of Heavy Metals in Zinc Fertilizers Made From Industrial By-Products
1985
Mortvedt, J. J. (John J.)
Many industrial by-products are being marketed as micronutrient fertilizers because of regulations which restrict indiscriminate disposal of wastes. Some of these materials contain other heavy metals which might be absorbed by crops and thus possibly enter the human food chain. Two greenhouse pot experiments were conducted to determine if corn (Zea mays L.) and Swiss chard (Beta vulgaris L.) absorbed significant quantities of Cd, Ni, and Pb from Zn fertilizers prepared from industrial by-products. Corn forage yields increased with Zn applications on alkaline (pH 7.4) but not on acid (pH 5.8) Mountview silt loam (Typic Paleudults). Concentrations of Cd in immature corn forage were not affected by applications of Zn fertilizers containing from 1 to 2165 mg kg⁻¹ of Cd. Dry matter yields of several harvests of Swiss chard were not affected by Zn applications at either soil pH level. Zinc concentrations in plant tissue increased with Zn applications but were lower in both crops grown on alkaline soil than in those grown on acid soil. Plant uptake of Cd generally increased with increasing levels of Cd in the Zn fertilizers on the acid soil only, with some concentrations > 2 mg kg⁻¹ in chard tissue grown on acid soil. Uptake of Ni and Pb by both crops generally was not affected, even with Ni and Pb levels in some by-products as high as 8950 mg kg⁻¹ and 52 000 mg kg⁻¹, respectively. These results suggest that plant uptake of heavy metal contaminants in Zn fertilizers made from some industrial by-products is minimal, except for Cd in some leafy vegetables grown on acid soils. Since corn and most vegetable crops usually are not fertilized with Zn if grown on acid soils, plant uptake of heavy metal contaminants in by-product Zn fertilizers should not be a significant problem.
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