3. Results and discussion
The results showed no significant differences in the metal content of the soils between the studied
treatments and all organic pollutants were under the detection limits. Previous studies from the same field
experiment after 4 years of organic waste application indicated similar trends (Odlare et al., 2008). The
compost contained large concentrations of heavy metals, especially Zn and Pb. Sewage sludge contained
large amounts of Cu. Plots amended with compost as the sole fertilizer exceeded the Swedish
Environmental Protection Agency’s threshold values for all heavy metals, whereas plots amended with
sewage sludge exceeded the threshold value for Cu. In Odlare et al. (2013) the metal content in soil prior
to the experiment was presented as well as mean metal levels in the harvest during the first four years. In
general, treatments with compost and sewage sludge received the highest mean amounts of metals, with
sewage sludge receiving higher rates of Cu and Zn, and treatment compost higher rates of Ni, Pb and Cr.