Worms promote vegetation by perforating and loosening the soil. The earth without worms would soon become cold, hardbound, and void of fermentation, and consequently sterile. Earthworms produce more compost in a shorter time and with less effort.
In classical Greek times, Aristotle called the earthworm “the guts of the soil”.
Even when organic matter is available, earthworms consume large amounts of soil, and by mixing the two produce rich humus of perfect texture with more plant nutrients.
It is estimated earthworms in one acre produce 5 MT of vermi castings or more than 5% of the total soil volume to plow depth.
Many pesticides and most chemical fertilizers inhibit, if not kill, the usually healthy and long-lived, earthworms. 260 PPM copper sulphate can drastically reduce the worm population and any nitrogenous fertilizer will quickly wipe it out.