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Earthworm Activity Increases Soil Health

By A. Tyler Labenz, Resource Soil Scientist
Natural Resources Conservation Service
Hutchinson, Kansas

Soil health as defined by the Natural Resources Conservation Service (NRCS) is the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation. Perhaps no other living organism in the soil is as important as an earthworm in helping to increase soil health. Earthworms increase soil aeration, infiltration, structure, nutrient cycling, water movement, and plant growth.

Earthworms are one of the major decomposers of organic matter. They get their nutrition from microorganisms that live on organic matter and in soil material. When they move through the soil eating, earthworms form tubular channels or burrows. These burrows can persist for a long time in the soil. Earthworm burrows increase soil porosity which increases the amount of air and water that get into the soil. Increased porosity also lowers bulk density and increases root development. Earthworm excrement or casts increase soil fertility because it contains nitrogen, phosphorus, potassium, and magnesium. Earthworm casts also contain microorganisms which increase in abundance as organic matter is digested in their intestines. The cycling of nutrients from organic matter and the increase in microorganisms facilitates plant growth. Earthworm casts along with binding agents released by earthworms also improve soil structure and increase aggregate stability.

There are three different species of earthworms which live in different locations in the soil and have different feeding and burrowing habits. Epigeic species live in the surface of the soil, are typically small, feed on decomposed plant material, and are adapted to the moisture and temperature changes that occur in the soil surface. Endogeic species live in the upper part of the soil and feed on organic matter and soil material. They form temporary burrows which are filled with worm casts as they move through the soil. Anecic species are deep burrowing and form permanent burrows that can extend several feet into the soil. They mainly feed on surface residue that they pull back into the burrow. They plug the opening of the burrow with organic matter or worm casts.

No-till and other conservation practices that increase plant residue and soil structure create ideal conditions that improve earthworm habitat. Having an abundance of earthworms is a good indicator of soil health.

For more information on how you can increase earthworm population, please contact your local NRCS office or conservation district office located at your local county U.S. Department of Agriculture (USDA) Service Center (listed in the telephone book under United States Government or on the internet at offices.usda.gov). More information is also available on the Kansas Web site at www.ks.nrcs.usda.gov. Follow us on Twitter @NRCS_Kansas. USDA is an equal opportunity provider and employer.