CADMIUM AND ZINC AVAILABILITY TO CORN FOLLOWING TERMINATION OF SEWAGE-SLUDGE APPLICATIONS

Corn and soil were sampled for 6 yr following termination of three annual applications of sewage sludge. Sludge treatments consistently resulted in greater Cd and Zn accumulation in stover than did the control treatment for each of the 6 yr following the final sludge application. Cadmium and Zn concentration in stover increased linearly within treatment levels for all years. Zinc uptake declined slightly over time, although not to the same degree or with the same predictability as Cd uptake. Soil Cd and Zn extractable with DTPA and 1 M HNO//3 were highly correlated with plant metal uptake within years. However, metal uptake diminished with consecutive croppings for constant levels of extractable Cd and Zn.