Interactions between earthworms and their soil environment

Laboratory experiments were used to study the effect of food quantity and quality on the biomass of earthworms, and the influence of earthworms on plant growth and infiltration of water into soil. Earthworms with the most food gained weight faster than those with little or no supplementary food. The latter also failed to become reproductively mature. Earthworms lost weight on a nitrogenpoor diet, but this was not rectified by supplementing such food with inorganic nitrogen added to the soil 2 weeks before the worms. Ryegrass grown in soil in which earthworms (Allolobophora trapezoides) had been kept grew more slowly than in soil which had no previous worm activity, perhaps indicating that earthworms had converted relatively-available organic N into less available forms.Microscolex dubius gave the fastest infiltration rates of water into soil when clover mulch was present. With Eisenia foetida there was little effect of worm density on infiltration rates; the highest density significantly increased infiltration but only when clover hay had been mixed in the soil. The surface casting behaviour of the two earthworm species varied with the placing of the food offered.