Pesticide and Environmental Update
Role of
Earthworms in Soil Explored
By Don Comis
The right earthworms can make home septic systems work better. The
wrong ones could do the opposite.
That’s the finding in a study of worm populations living in the soil
near trenches receiving septic tank flow outside five single family homes
in Arkansas. Carrie L. Hawkins of the University of Arkansas at
Fayetteville performed the study in collaboration with Agricultural
Research Service (ARS) soil scientist Martin J. Shipitalo of the North
Appalachian Experimental Watershed in Coshocton, Ohio.
The scientists found that the worms were favoring the area near the
trenches because they were feeding on the household wastes discharged in
the trenches. They found fives species of earthworms. None of the species
were deep-burrowers like nightcrawlers.
Their burrowing near the surface actually helped the septic wastewater
spread through the soil more evenly, resulting in better cleansing of the
water. Had they been nightcrawlers, the worm burrows might have drained
the trenches so fast that it would bypass the soil filtering.
The results of this study will be published in the journal Applied Soil
Ecology and are currently online.
The earthworm study is part of a longstanding series of worm studies
across the country by Shipitalo, ARS colleagues at Coshocton and
elsewhere, and cooperating university scientists.
This body of earthworm knowledge is one of many aspects of ARS research
on soils that is incorporated into the Smithsonian Institution's Soil
Exhibition, which opens on July 19 and ends December 31, 2010. The
exhibition is at the Smithsonian's National Museum of Natural History in
Washington, D.C., and is called "Dig
it! The Secrets of Soils."
Ted Zobeck and Michael Russelle, at ARS labs in Texas and Minnesota,
respectively, are state liaisons for the exhibit. ARS scientists at the
National Soil Tilth Laboratory in Ames, Iowa, contributed heavily to the
exhibition, as did the late Dennis Linden in Minnesota.
The U.S. Department of Agriculture (USDA) is a lead sponsor of the
exhibition through the Soil Science Society of America.
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