The utilization of different types of wastes as a source of nutrients for crop production is considered with increasing interest particularly, where a decrease of humic materials in soils is due to practices of intensive agriculture. However, the presence of heavy metals in wastes can contaminate the food chain with dangerous consequences for the health of animals and men. Concentration of heavy metals in wastes is very variable A better understanding of the effect of heavy metals in soil after waste application could be achieved only from knowledge of the chemical form of these elements which determines their mobility and hence a possible crop contamination.