Sewage sludge application on soil:: Effects on two earthworm species

Some biological effects of soil fertilisation with sewage sludge were investigated after soil reclamation in an opencast mining area. Two earthworm species (Allolobophora chlorotica chlorotica and Nicodrilus caliginosus meridionalis) inhabiting the reclaimed soil were tested for their response to two high doses of sludge (75 and 150 g kg(-)1 of dry sludge in dry sieved soil). The metal concentrations in the sludge amended soils were below that which worm mortality would be expected. Mean annual density of the earthworms was higher in the plots where the sludge was applied (435 and 335 ind. m(-2)) than in control (115 ind. m(-2)). We verified the accumulation of Cd and Zn by the two earthworm species at any dose of sludge, and metal accumulation was higher in N. caliginosus than in A. chlorotica. Zn, Pb, Cr, Cu and Ni were more concentrated in the earthworm egesta than in the bulk soil.