What are Earthworms?

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Earthworms are tubular, segmented, soil-burrowing members of the phylum Annelida. Through their movements and actions in the soil earthworms have the ability to alter soil characteristics by decomposing organic matter, stimulating microbial activity, mixing mineral particles and organic matter, enhancing soil porosity and infiltration, aerating the soil, increasing soil water holding capacity, and improving overall soil tilth.

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Regional Educator ResourcesOther Educator ResourcesTechnical Resources
Title Source Resource type and Date Short Summary / Preview
Earthworm and Daikon Radish Cover Crop Video Purdue Video

Jul 2012

This video is about earthworms and a radish cover crop in Indiana.

Earthworms and Crop Management Purdue Extension Publication

Oct 1993


This publication provides basic information on earthworm ecology, the effects of earthworms on soil properties and processes, and the influence of soil management practices on earthworms. It concludes with a section on how to encourage the buildup of earthworm populations in agricultural fields, as well as some remaining questions that require further study.

Can’t live without me: Why Herman and other worms are so important to us University of Illinois Student Resource

Not Dated


Resource for students on the importance of earthworms.

The “dirt” about earthworms Michigan State University Extension News Article

Nov 2013


Although earthworms are beneficial in gardens and agricultural fields, they are harmful to Michigan’s forests where they are an invasive species.

Earthworms can be an indicator of soil health Michigan State University Extension News Article

Jun 2016


Simple steps to determine worm populations in your field

Soil Health Nexus Demonstration How-To: Earthworm Counts Soil Health Nexus How-to Video

May 2019

Techniques to count earthworms. An assumption is that the more worms you have, the more healthy your soil is. However, while we think worm counts are a good indicator of soil health, that is actually not the case. Worms need to live in damp, loamy, moist soil, so you might have healthy soil that is still not a good habitat for earthworms.

The Living Soil: Earthworms NRCS NRCS Webpage

Not Dated


Earthworms dramatically alter soil structure, water movement, nutrient dynamics, and plant growth. They are not essential to all healthy soil systems, but their presence is usually an indicator of a healthy system.

Earthworms – NRCS & others Webpage

Sep 2011


Earthworms play a key role in modifying the physical structure of soils by producing new aggregates and pores, which improves soil tilth, aeration, infiltration, and drainage. Earthworms produce binding agents responsible for the formation of water-stable macro-aggregates. They improve soil porosity by burrowing and mixing soil. As they feed, earthworms participate in plant residue decomposition, nutrient cycling, and redistribution of nutrients in the soil profile. Their casts, as well as dead or decaying earthworms, are a source of nutrients.

Soil Quality Indicators: Biological Indicators and Soil Functions USDA NRCS Fact Sheet

Feb 2015


Fact sheet. Soil biological indicators provide insight into the living component of the soil. Similar to physical and chemical indicators, biological indicators have a relationship to soil functions and can evaluate soil functions to assess
soil quality.

Soil Quality Indicators: Earthworms USDA NRCS Fact Sheet

Apr 2009


Fact sheet. Earthworms are native to non-glaciated areas of North America, but non-native species from Europe and Asia also exist here. Earthworms are classified into three groups based on their habitat.

The Science of Soil Health: Nightcrawlers and Water Flow NRCS video series “Unlock the Science of Soil Health” Video

Jul 2014

Dr. Eileen Kladivko, Purdue University discusses the effect night crawlers have on aiding water flow into and through soils.

Title Source Resource type and date Short Summary
Global Soil Biodiversity Atlas Publications Office of the European Union Book Excerpt

May 2016

Soil biodiversity is crucial to soil health and earthworms play a role in that biodiversity.
Building Healthy Soils University of Tennessee Extension Fact Sheet

Sep 2012


Larger organisms such as earthworms create burrows in the soil, enhancing water infiltration and soil aeration, redistributing organic materials and nutrients throughout the topsoil and providing pathways for root penetration.

Earthworms Penn State Extension Fact Sheet

Sep 2013


The burrowing and feeding activity of earthworms have numerous beneficial effects on overall soil quality for crop production.

Earthworms: Thatch busters University of Kentucky Extension Fact Sheet

Not Dated


Earthworms, called the “intestines of the earth” by Aristotle, are very important soil organisms that aid in the decomposition of plant litter, such as the thatch layer, and in recycling of nutrients.

Title Source Resource type and Date Short Summary
Soil Macrofauna Field Manual Food and Agriculture Organization of the United Nations (FAO) Field Manual


This field manual looks at soil health and how macrofauna affects it.
Agricultural Management Effects on Earthworm Populations USDA NRCS Technical Note

Jun 2001


For earthworms to be abundant, a field must meet several conditions that are also associated with soil quality and agricultural sustainability: moderate pH, surface residue for food and protection, and soil that is not waterlogged, compacted, droughty, or excessively sandy.

This page reviewed by Liz Schultheis and Kenny Eck.

Last reviewed 2/28/20