These species ingest large amounts of soil, showing a preference for soil rich in organic matter. Endogeics may have a major impact on the decomposition of dead plant roots, but are not important in the incorporation of surface litter. Anecic earthworms build permanent, vertical burrows that extend deep into the soil. This type of worm comes to the surface to feed on manure, leaf litter, and other organic matter. Anecics, such as the nightcrawlers, Lumbricus terrestris and Aporrectodea longa, have profound effects on decomposition of organic matter and the formation of soil.
Deep tillage is generally harmful to earthworms.
It can kill them outright, disrupt their burrows, lower soil moisture, and reduce the availability of surface litter. Shallow tillage, ridge-tillage, and surface management of crop residues has often led to increases in earthworm activity compared to areas where deep tillage is practiced. Earthworms favor leaf litter that has a low ratio of carbon to nitrogen, and tend to prefer residues of clovers and other legumes over residues of grass. Residues left as surface mulch are very useful in enhancing earthworm densities. Certain pesticides are particularly harmful to earthworm populations.