Search

To study the feasibility of earthworm introduction for increasing the macroporosity and permeability of arable heavy clay, deep-burrowing earthworms ( Lumbricus terrestris L.) were inoculated into a tile drained experimental field in Jokioinen, S-W Finland in autumn 1996. Inoculation with the Earthworm Inoculation Unit technique was at the up-slope end of the field, in the field margins under permanent grass, and inside the four 0.46 ha plots of the field. The experiment was monitored on three occasions. In 1998 the L. terrestris population had persisted in low numbers only in field and plot margins. By 2003, when the field had been under set-aside grass for three years, density had grown in the margins and L. terrestris were also found inside the field at a very low density. The third monitoring was in autumn 2009, after a further four years as set-aside and a subsequent division of the field into no-till and ploughing management, and looked at the effects of management (margins, no-till, ploughing), distance from the inoculation and sub-drainage on L. terrestris abundance. The abundance displayed a clear gradient over the field, declining from 14 ind. and 18 g m −2 at 5–9 m from inoculation, to 1 ind. and 2 g m −2 at 56–60 m distance. Margins had the highest abundances (16 ind. and 32 g m −2 ), followed by no-till (4 ind. and 4 g m −2 ) and ploughing (1 ind. and 1 g m −2 ). Abundances were significantly higher above the tiles than between them ( P

Summary The morphology of Lumbricus terrestris L. burrows was investigated in relation to subsurface tile drain position. The aim was to clarify the causes and consequences of higher densities of L. terrestris previously measured above the tiles at the study site. At two pairs of study pits, the plough layer was removed from a 1 m × 2 m area above the tile and at 8 m distance from it. Burrows of L. terrestris were identified at the plough pan, resident worms removed and burrows cast with dyed fibreglass resin. The resin casts were exposed in the profile, depth and length of casts measured and their connections with tiles recorded. In both above-tile pits, two cases were recorded where the cast burrow ended at the tile surface. These contacts indicate the potential importance of burrows in the conduction of water and solutes from the soil surface layers into the tiles. The mean depth of burrows was 1.0 m (se = 0.024, n = 27) above the tiles and 0.83 m (se = 0.036, n = 12) between the tiles. During adverse soil conditions such as droughts, individuals living near the tiles may gain from the shelter provided by their deeper burrows and this could partly explain the higher population densities above the tiles.

Summary Lumbricus terrestris L. is noted for activities on the soil surface and descriptions of feeding, movement and mating have previously been recorded. The aim of this study was to investigate the effects of resource availability on these behaviours using an experimental system. The laboratory set-up consisted of an arena with a continuous area of 1 m2 with soil-filled tubes to a depth of 1 m. Eighteen mature, field-collected L. terrestris were used and fed with dried barley straw on the soil surface, either evenly or in one patch. Both patterns were applied twice over an experimental period of 56 days. An infrared video system was used to provide permanent records of a 12:12 hrs dark : light cycle. Earthworm behaviour was classified into three major groups; foraging/exploration, over-surface movements and mating, with time spent in each activity recorded for all individuals. Seventeen earthworms survived to the end of the experimental period. Surface activity peaked one hour after darkness and diminished steadily until lights up. Foraging activity increased by a factor of 1.6 in a resource-rich area whereas away from the patch it reduced by a factor of 0.8 compared with even straw distribution. Over-surface movement increased by a factor of nine after provision of a patchy straw distribution, with two thirds of movements initiated by individuals in a resource poor area. The majority of matings occurred early in the dark period. During even resource distribution, matings occurred equally in different parts of the arena whereas under patchy distribution, more matings were recorded in the resource-rich area. Presented results suggest that resource availability is an important factor affecting different aspects of surface behaviour in L terrestris.