EARTHWORM CHANNELS IN CULTIVATED CLAYEY AND LOAMY NORWEGIAN SOILS

Studies of earthworm species and their activity, expressed as channels , on cultivated loamy (Humic Cryaquept) and clayey soils (Typic Endoaq ualf and Typic Cryaquept) were conducted in southern and central Norwa y before conversion from conventional to organic cropping systems. At all the three study areas: Landvik (Grimstad), Voll (As) and Kvithamar (Stjordal), the earthworm species Aporrectodea caliginosa, Aporrectod ea rosea, Allolobophora chlorotica and Lumbricus rubellus were found. At Landvik, where the deep-burrowing species Aporrectodea longa, A. ca liginosa and Lumbricus terrestris dominated, medium (4-6 mm) and coars e (>6 mm) earthworm channels were most numerous below the plough layer . Almost no coarse pores were found at Voll and Kvithamar. The volume of earthworm channels below the plough layer was 0.6-0.8% of total soi l volume at Landvik and Voll and 0.3-0.4% at Kvithamar. Earthworm chan nels > 6 mm below the plough layer were useful to identify present and previous activity of deep-burrowing earthworms such as L. terrestris. Below the plough layer, roots were almost entirely restricted to eart hworm channels and interaggregate spaces. (C) 1997 Elsevier Science B. V.