Earthworms eat organic matter like plant material, microorganisms and dead animals that are found in soil, but they don’t actually eat the soil. However, their droppings, called castings, become a part of the soil, which benefits living plants, according to HowStuffWorks.
Earthworms that live at the surface layer of soil eat fallen leaves and decaying animal material that falls to the ground. Their digestive processes break these materials down into basic nutrients that plant roots can absorb.
Just below the upper layer of loose soil and leaves, there is a second layer of soil where a different type of earthworm eats dead plant roots. These earthworms do not move to the surface to collect or eat plant material.
The next layer of soil is home to a third type of earthworm that digs semi-permanent tunnel systems. They drag organic materials down into areas where they can store them and eat them when hungry.