Bioabfallkompost im biologischen Landbau – Auswirkungen auf die Gehalte von bioverfügbaren Schwermetallen im Boden

Summary

The accumulation of heavy metals in soils is a potential risk that may keep organic
farmers from using biowaste compost. As the ecological effects of metals are related
to mobile fractions rather than to total contents in the soil, we measured the total
(aqua regia extractable) heavy metal contents, the readily available water soluble and
the potentially bioavailable LiCl-extractable fraction of soil heavy metals in a field
experiment after ten years with total applications of 95, 175 and 255 t ha-1 biowaste
compost (fresh matter). Total soil contents of Cd, Cr, Cu, Ni and Pb in the compost
treatments were not significantly higher than in the unfertilized control. Total Zn
contents increased in the treatment with the highest application rate. In the mobile
fractions Cd and Pb were not detectable. Cr, Ni and Zn contents were in the range
published for unpolluted soils in other studies and did not show any differences
according to treatment. Easily exchangeable Cu (in LiCl extract) was increased with
compost fertilization. In several crops, lower Cd contents were measured with
compost fertilization than without fertilization. Potatoes which had received mineral
fertilizer had significantly higher Cd contents. Crop Zn contents were increased in the
compost treatments. In conclusion, fertilization with high quality biowaste compost at
such rates and after ten years of application gives no cause for concern with regard to
both total heavy metal contents and available heavy metal fractions.