But the worm does so much more by helping to complete the decomposing process of our organic waste, eating bacteria and fungi and mass producing these microscopic life forms in their gut and pooping it out in the form of castings.
Castings, often called gardeners gold because of its value has a unique shape of its own. Torpedo shaped and covered in a substance that slowly breaks down like a time release fertilizer, the casting helps build the soil both in physical structure and chemical make-up.
Two books I recommend for soil education are:
The Earth Moved: On the Remarkable Achievements of Earthworms
Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, Revised Edition
Worms, the soil, gardening...these can not be separated. If you do one you must do all three.
Chemical fertilizers, herbicides, pesticides all kill the naturally occurring life in the soil.
Mother nature really does know best and if assistance from man comes is the form that mimics mother nature then you feed the cycle instead of breaking it.
Feed your garden and it will feed you. Let the worms help!