EARTHWORM POPULATIONS AND SURFACE-ACTIVITY IN RELATION WITH SEWAGE-SLUDGE AND OTHER FERTILIZERS

This study, that belongs to a more general one dealing mainly with Macroarthropods, aims to better the knowledge of sewage sludge's influence on earthworm populations. In the experimental conditions, the spreading of sewage sludge associated with farmyard manure appears to have a positive effect on earthworm populations. Particularly, Allolobophora chlorotica seems to thrive with the sewage sludge. In agreement with other studies, organic fertilizers favor more earthworms than mineral ones. Other land use practices (ploughing, crops rotation, etc.) have also an influence on the populations. On the other hand, surface activity of earthworms was studied with Barber pit falls. All the present species are active at the surface of the soil with the highest activity recorded with the epigeic earthworms and the lowest with the endogeic ones. Rainfall and temperature determine earthworms' surface activity which may be qualified as "hygrophilous" and "thermophobe".