TRACE-ELEMENT FATE IN SOIL-PROFILE AND CORN PLANT AFTER MASSIVE APPLICATIONS OF URBAN WASTE COMPOST - A 6-YEAR STUDY

A six-year trial was performed to evaluate heavy metal accumulation in soil, the movement of these metals within the soil profile and their availability to corn plants through repeated urban waste compost appli cations. The findings showed that the amendment of a calcareous soil w ith 30 and 90 t ha(-1) yr(-1) of compost does not cause corn plant pol lution, nor presumably groundwater pollution. Indeed, the heavy metals added did not leach below the ploughed layer of the soil. Increased c oncentrations of trace metals in the corn plant were limited to copper , lead and zinc. Only copper reached a higher concentration in the tre ated corn grain than in the control, however this remained within the range normally found in corn. The compost application caused no visibl e phytotoxic effects on corn plants, and lead to a significant increas e in grain yield.