LONG-TERM EFFECTS OF BIOLOGICAL AND CONVENTIONAL FARMING ON EARTHWORM POPULATIONS

In a long-term trial the earthworm populations of two biological farming systems, two conventional systems and one control treatment were compared. The experimental site contained a Luvisol from loess under arable land. The earthworms were investigated by handsorting three times in 1990 and 1991 after beetroot and winterwheat. The main differences within the treatments were fertilization and plant-protection management. All treatments received the same crop-rotation and a similar soil cultivation. The input of organic matter was similar in the three organically manured treatments. Significantly higher earthworm biomass, earthworm densities and presence of anecic species were found in the biological plots than in the conventional and control plots in spring and autumn of 1991. The control plot (no fertilizer during 12 years) had a similar earthworm-population as the conventional treatments. Apparently, plant protection seems to be the main factor responsible for the differences between the treatments. Nicodrilus longus, N. nocturnus, N. caliginosus and Allolobophora rosea were the dominant earthworm species in all treatments.