Influence of organic matter on earthworm production and behaviour: a laboratory-based approach with applications for soil restoration

Restored soils are often low in organic matter (OM). As a result, OM is applied to increase soil fertility. Earthworms can assist soil incorporation of OM, but feeding behaviours, and as a result their roles in this process, differ between species. Laboratory experiments examined the effects of OM availability on the growth and behaviour of Aporrectodea longa and Lumbricus terrestris. Hatchling growth was recorded from 1 l vessels containing soil and OM (separated cattle solids), either surface applied (SUR) or mixed into the soil (MIX). Growth of L. terrestris was also recorded where separated cattle solids (SCS) were concentrated in bands at the surface (SUR) or at depths of 0.03 (UPP) or 0.08 m (LOW). In a further experiment, L. terrestris and L. rubellus were kept in mono-species cultures and paired combination, in treatments with selected SCS placements, which allowed assessment of OM position on species interactions. After 28 weeks, both L. terrestris and A. longa exhibited significantly greater growth rates (P < 0.05) in SUR treatments. The behaviour of both species changed with time. L. terrestris were located in areas where OM was concentrated. After 24 weeks, mean masses of 3.1, 2.2 and 1.6 g were recorded for SUR, UPP and LOW treatments, respectively. Where L. rubellus and L. terrestris were co-cultured, the former had significant (P < 0.05) negative effects on the growth of the latter, but only when surface OM was limited. At restored sites, application of OM may be important in the development of sustainable earthworm populations and hence their role in soil amelioration.