As earthworms crawl through the soil eating, they burrow and tunnel bringing improvements to the soil.
Increase infiltration of rainwater
Improve soil aeration
Allow roots to grow deeper
Incorporate minerals and nutrients at greater soil depths
Increase microbial activity
Create a way for plants to better resist stresses such as draught and disease
Since earthworms are negatively impacted by insecticides, fungicides, herbicides, and fertilizers, landowners should be very reluctant to use any chemicals on a worm rich property.