Fertility gain and heavy metal accumulation in plants and soil, studied by means of a compost amended cultivation of Taraxacum officinale

Abstract

A pot study was conducted to evaluate the effect of compost, as an organic amendment, on biomass production and on total and available Cu, Zn, Pb, Cd and Cr concentrations in agricultural soils. The available fraction of metals in the soil was measured, both using the DTPA‐TEA extraction procedure and determining metal accumulation in the indicator plant Taraxacum officinale (the common dandelion). The results indicate a strong effect of the compost on biomass production: a 58% and 100% increase in epigenous biomass per unit area was achieved in treatments using 36 g and 55 g compost per kg of soil, respectively. While the total and DTPA‐extractable Cu, Zn and Pb did increase in amended soils as compared to the control, the leaf concentration of Zn and Cu slightly decreased after increasing compost additions. No significant relation was found between the amount of compost addition and the Cr and Cd concentration in the soils, but the Cd uptake by the dandelion decreased with increasing compost applications. These results suggest that metals introduced in soils treated with compost are only available to plants to a small extent, but can significantly increase the total concentration in soils after repeated treatments. Considering that soils have a limited resilience to contain and transform metals, any increase in their total concentration is of concern, since the metals can become mobile and bioavailable to organisms when the soil buffering capacity is lost.