This was more pronounced in the V2 and NV1 soils (p b 0.05) and may be due to compounds in the applied amendments (Ross, 1994) than to a vegetation effect, since this response was observed in both vegetated and non-vegetated sites. In general, COWand POULTRY treatments were more effective reducing Pb bioavailability in non-vegetated sites, while, in vegetated sites, COW-treated plots showed the highest decrease in metal bioavailability at 6 months (Fig. 4). The input of organic matter under COW treatment might have contributed to metal immobilization in soil through sorption processes.