Role of Earthworms in Soil Explored

The right earthworms can make homeseptic systems work better. The wrong ones could do the opposite.

That’s the finding in a study of worm populations living in the soilnear trenches receiving septic tank flow outside five single family homes inArkansas. Carrie L. Hawkins of the University of Arkansas at Fayettevilleperformed the study in collaboration with Agricultural Research Service (ARS) soilscientistMartinJ. Shipitalo of theNorthAppalachian Experimental Watershed in Coshocton, Ohio.

The scientists found that the worms were favoring the area near the trenchesbecause they were feeding on the household wastes discharged in the trenches.They found fives species of earthworms. None of the species were deep-burrowerslike nightcrawlers.

Their burrowing near the surface actually helped the septic wastewaterspread through the soil more evenly, resulting in better cleansing of thewater. Had they been nightcrawlers, the worm burrows might have drained thetrenches so fast that it would bypass the soil filtering.

The results of this study will be published in the journal AppliedSoil Ecology and are currently online.

The earthworm study is part of a longstanding series of worm studies acrossthe country by Shipitalo, ARS colleagues at Coshocton and elsewhere, andcooperating university scientists.

This body of earthworm knowledge is one of many aspects of ARS research onsoils that is incorporated into the SmithsonianInstitution'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 inWashington, D.C., and is called "Digit! The Secrets of Soils."

TedZobeck andMichaelRusselle, at ARS labs in Texas and Minnesota, respectively, are stateliaisons for the exhibit. ARS scientists at theNationalSoil 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 theSoil Science Society of America.

ARS is a scientific research agency of the USDA.