POTENTIAL OF DISCARIA AMERICANA FOR METAL STABILIZATION ON SOILS AMENDED WITH BIOSOLIDS AND ASH-SPIKED BIOSOLIDS

Biosolids (B) may contain various types of environmental pollutants, which can exert phytotoxic effects in plants. The effect of aqueous extracts on seed germination and the primary root growth of discaria (Discaria americana) obtained from different soil-application rates of B and a mixture of B and incinerated B were investigated. The objective was to evaluate the potential use of discaria for the stabilization of B-amended soils. Ryegrass (Lolium perenne L.) was used for comparison. Compared to ryegrass, relative seed germination (RSG) was significantly lower for discaria. RSG of discaria and rye grass was inversely correlated to the electrical conductivity of extracts, although a significant adverse effect was only observed for ryegrass with the highest dose of the mixture of B and incinerated B. This dose also produced a reduction in the germination index of discaria, which could not be correlated with the parameters studied. The B extracts did not exert any significant adverse effect on the relative root growth of both species. An increase in relative root growth and germination index was observed for discaria with a field application rate equivalent of 156 t DW ha^-1 of B, suggesting a stimulating effect of the amendment. The results obtained in this study suggest that germinated seedlings of discaria might be used for the stabilization of B-amended soils. However, further greenhouse and field experiments should be performed to confirm these findings.