HEAVY-METALS IN CROPS AS AFFECTED BY SOIL TYPES AND SEWAGE-SLUDGE RATES

A municipal sewage sludge was applied at three application rates to th ree soils in field lysimeters to study the effects of soil and sludge application rate on cadmium (Cd), copper (Cu), nickel (Ni), and zinc ( Zn) absorbed by 'Larker' barley (Hordeum vulgare L.) and by Swiss char d (Beta vulgaris L. 'Cicla'). Sludge applied at 20, 40, and 100 Mg/ha oven-dry equivalent were mixed into the top 0.15 m of soil in each lys imeter. In addition, a nil sludge rate (control) received 125 kg N/ha. Metal contents were relatively low in barley grain, higher in barley straw, and highest in Swiss chard. Metal contents in plants increased with increasing sludge loading. Most plants grown on soil amended with the higher sludge rates were too high in Cd (greater than 0.5 mg/kg o f dry feed material) to be suitable for animal consumption. No plant m aterials tested exceeded the suggested maximum Zn, Cu, or Ni levels.