Earthworms play an important role in the soil. They contribute to litter degradation, soil blend, formation of stable crumbs, soil aeration and drainage. However, with increasing soil acidifcation the earthworm population decreases. Below a soil pH of 4 only sporadic earthworms can be found. In 33 of the plots less than 10 earthworms per m2 and in 15 none were observed.
