The Availability of Sludge-Borne Metals to Various Vegetable Crops
1975
The uptake of metals by seven vegetable crops was studied after 0, 112, 225, and 450 tonnes/ha (110C basis) of sewage sludge was applied to a coarse, sandy soil. Sewage sludge additions did not adversely affect either potato yields or specific gravity. Generally, metal contents of the vegetative tissue were higher than those of the fruiting, root, and tuber tissue. In most edible tissue heavy metal accumulations did not increase more than two- or threefold as a result of amending the soil with 450 tonnes/ha sludge. Lettuce tissue was an exception, with increases from 21 to 225 ppm, 1.6 to 11.9 ppm, and 0.61 to 2.67 ppm for Zn, Cu, and Cd, respectively. Lettuce is an accumulator of metals, whereas potatoes and carrots are excellent nonaccumulators and may be very desirable crops for utilizing sludge-amended soils. Approximately three times as much Zn accumulated in pea vine tissue as in the edible fruit. The increased accumulation was linear over the sludge application range studied. The Cd/Zn ratios for edible portions of radishes, potatoes, peas, and corn grown on sludge-amended soil did not exceed that of the applied sludge (0.007).
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