Summary

Summing up data of numerous researches on the dominant earthworm species
in agricultural lands in Scandinavia, Central Europe and Eastern Europe, it has to be
concluded that the most common species is Aporrectodea caliginosa. Whereas in
acidic soils increases proportion of Dendrobaena octaedra and Lumbricus rubellus.
1.1. Earthworm impact on soil properties and microorganisms
Even in insignificant density earthworms may have great impact on soil aeration and
water infiltration. Earthworm presence may reduce soil compaction which has
occured due to agrotechnical activities. Earthworms have great impact on soil horizon
mixing, and dragging of the the upper layer, which is rich in organic matter, into the
deepest horizons (Lee, 1985; Curry, 1988).
Earthworms may have a significant impact on the chemical properties of the
soil. They drag down into the soil plenty of partly dispersed plant remains. In the
digestive tracts the remains are being macerated, mixed up with mineral particles of
the soil, enriched with Ca 2+ ions from calcium glands and returned to the soil as casts
(Stewart et al., 1980). Casts presence in the soil significantly improves its fertility.
The casts have a positive impact on aeration, water infiltration, quantity of water.
Increases soil active surface area, development of pore and channel system, which
allows the roots of plants to penetrate into the soil. In casts is being observed bacteria
and soil microscopic fungus activity increase. As well as the activity of
microorganisms is being stimulated in earthworm digestive tracts (Lee, 1985;
Schrader, Seibel, 2001). Increased activity of microbiological and digestive enzymes
is being observed in the central intestine of earthworms (Curry, Schmidt, 2007).
Researches indicate not only on symbiotic relations of earthworms and
microogranisms, but also on active use of microorgranisms as nutrition- especially
the species Aporrectodea caliginosa, which feeds on well decomposed detritus with
high concentration of microorganisms (Kristufek et al., 1994; Kristufek et al., 1995).
Other products of earthworm metabolism also descend into the soil (Lee, 1985).
Earthworms induce total oxygen mineralization in agricultural ecosystems. The
earthworm feeding activity increases content of oxygen available to plants in the soil,
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