Ecological risks of the use of sewage sludge as fertilizer in soil restoration: effects on the soil microarthropod populations

Abstract

Experimental plots were laid out in a limestone quarry in Girona (Catalonia, Spain) to test the effects of sewage sludge on the soil microarthropod populations. Two different doses of sludge (7·5 per cent and 15 per cent) were applied to fertilize soil that was used to restore a quarry after opencast mining. Mean annual arthropod density increased when sludge was applied, but the 15 per cent dose caused an impoverishment of the community structure and a decrease of the soil oribatid diversity. Julidae (Diplopoda) and large predators of the mite family Parasitidae (Mesostigmata) were the most depressed taxa, whereas some groups depending on the availability or quality of organic matter (such as the immature Coleoptera or the Uropodidae), or on water availability (such as Collembola) were stimulated. Among the oribatids, Punctoribates sp. was the most depressed, whereas the more common little Oppias were significantly favoured. The application of sludge at a dose of 15 per cent must be avoided in order to preserve the soil biodiversity. Copyright © 1999 John Wiley & Sons, Ltd.