Many people assume that all bugs and insects are bad for their lawns, but they are wrong, some insects are actually very beneficial. It might not be the cutest and most cuddly creature, but the earthworm is one of the best helpers in yard work that you have.
Earthworms travel through your soil by digging tunnels. As they dig these tunnels they are actually aerating your soil for you.
Your grass and plants also do best in rich soil, which is composed of biological matter which has been broken down. Some species of earthworm come to the surface and graze on the higher concentrations of organic matter present there, mixing it with the mineral soil. Since there is a high level of organic matter mixing is associated with soil fertility, an abundance of earthworms is beneficial.
One common earthworm action is pulling down below any organic matter deposited on the dried dirt, such as a leaf or manure, either for food or when it needs to plug its burrow. Once in the burrow, the worm will shred the leaf and partially digest it, then mingle it with the earth by saturating it with intestinal secretions.
The soil which earthworms excrete is called casts. Casts are are 5 times richer in available nitrogen, 7 times richer in available phosphates and 11 times richer in available potash than the surrounding upper 6 inches (150 mm) of soil. One worm can produce up to 10 lbs of casts in a year.
“It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.” Charles Darwin