The lush meadows of New England, the vast farmlands of the upper Midwest, the great wheat fields of Canada are all attributed to the introduction of the earthworm. By the early part of the twentieth century, says Minnich, New Zealand soil scientists observed that European lumbricids were making vigorous inroads into the island's previously wormless soils. Hill pastures that could barely support a stand of grass were gradually becoming lush and green even though no fertilizer was applied. Counts of earthworms ran as high as over four million per acre, more than three times the maximum populations of the same species in their Old World habitats. The source of all this fertility was what the worms excreted in the form of castings, compost of the highest grade, containing mineral and organic matter in a soluble form, excellent as both a fertilizer and as a soil conditioner.
Earthworms can produce more compost, in a shorter time, with less effort, than any other method.
As they burrow, they are constantly bathed in mucus, which helps them through the roughest ground. Continually rubbed off, this mucus helps cement the walls of their tunnels. And, while it helps a worm worm its way out of a predator's grasp, it also helps hold the soil firm, retaining moisture as it hardens. An omnivorous and unfinicky eater, the eyeless earthworm ingests whatever appears before it in morsels fit for its toothless gums. Muscularly pumping through the soil, it ingests not only organic matter but the raw earth itself, using sand and other mineral particles as grinding stones in its gizzard.