Why are earthworms considered a farmers' best friend?

Earthworms are a gardeners best friend. They have a important part in improving garden soil. Worms exist in a lot of different types of soils but the healthier the soil the more earthworm activity you will see. A good healthy soil is a soil that is full of organic matter , has good aeration and retains moisture well. Earthworms don't have lungs. They breath through there skin by absorbing the oxygen in from the soil and releases carbon dioxide