EN
Earthworms are keystone species in the process of soil formation. The present paper reports on comparative studies of earthworm activity at a semi-natural park site and a typical farmland in Northern Poland. Of the six species found, Aporrectodea caliginosa, A. rosea, Allolobophora chlorotica, and Lumbricus terrestris occurred at all sites. The epigeic species L. casteneus and D. octaedra were missing at the farmland sites. Least species rich was the farmland site with the most condensed soil where only A. caliginosa, A. chlorotica, and L. terrestris were present. The farmlands showed reduced earthworm activities as measured by cast production and macropore density with respect to the natural park site. Cast production in the farmlands appeared to be independent of soil compactness and relative humidity. Soil compactness above 1.7 Mg · m-2 hampered earthworm activity. The total cast weight was inversely correlated with soil pH. The two most alkalic sites had significantly lower total cast weights per m2 than the park site.