Compost use in viticulture: Effect on heavy metal levels in soil and plants

The purpose of this study was to examine the long-term effect of compost application on the heavy metal content in soil, leaves, and fruit of grape (Vitis vinifera). Two types of compost were tested in a vineyard. One was compost with a low heavy metal content, which was derived from sewage sludge and bark (SB compost). The other type was compost with a higher concentration of metals, which was derived from municipal solid waste (MSW compost). For 6 years, the levels of zinc (Zn), copper (Cu), nickel (Ni), lead (Pb), cadmium (Cd), and chromium (Cr) in their total (aqua regia digestion), EDTA-extractable, and DTPA-extractable forms were monitored in soil, leaves, musts, and wines. The resulting data clearly demonstrate that SE compost did not cause any significant increase in heavy metal levels in the soil and the plants. Thus, this type of compost can be used for soil fertilization with no danger either to the environment or to crops. In contrast, the use of MSW compost caused a significant accumulation of Ni, Pb, Cd, and Or in the soil, in vegetation, and in musts. Skin-contact fermentation dramatically decreased the heavy metal content of the wines. The concentration of heavy metals in plant tissues was found to be positively correlated with the DTPA-extractable form of the metals in the soil, but not correlated with the total or the EDTA-extractable forms.