Earthworms provide many positive benefits to improve plant growth, including aerating the soil, improving drainage and providing nutrients the plants need. They help to turn the soil and bring mix organic materials from the surface so the forces of nature can break down these products to further enrich the soil.
Precipitation along with the activities of humans and other animals cause compaction of the particles of soil. This compacting allows air and water to circulate. The activities of worms loosen the soil, allowing the roots of plants to receive the necessary air and moisture to improve plant growth. The presence of earthworms in the soil of one's garden is an indicator that the soil is healthy.
Human activity often inhibits the working of worms in the soil. Excessive use of broad spectrum pesticides affects the population of earthworms in the soil. However, activities, such as adding mulch, help to encourage growth of the worm population. Worms prefer soil with a pH between 5 and 7, which is also suitable for flowers and vegetables. The addition of compost to the soil helps to lower the pH to a suitable range for worms to live. Switching to drip irrigation systems helps to prevent compacting of the soil to the point worms look for a different habitat.