Wednesday, November 15, 2006

Potential Effects of Earthworms on Soil Renovation of Household Wastewater.

Carrie Hawkins, University of Arkansas at Fayetteville, 911 W Hughes St. Apt 8, 911 W Hughes St. Apt 8, Fayetteville, AR 72701, United States of America, E. M. Rutledge, University of Arkansas, 104 Skyline, Fayetteville, AR 72701, Martin Shipitalo, USDA-ARS,N.Appalachian Exp.Wts, "PO Box 488, State Route 621", "PO Box 488, State Route 621", Coshocton, OH 43812-0488, United States of America, and Mary Savin, 115 Plant Science Building, University Of Arkansas, University Of Arkansas, Fayetteville, AR 72701, United States of America.

Because the large pores created by earthworms have been shown to increase water movement in the soil, there is concern that earthworms could affect soil renovation of septic tank effluent.   Additionally, the moist, nutrient rich environment in filter fields may attract earthworms, magnifying their effects.  Potential effects depend on the species.   Endogeic species make largely horizontal which may enhance renovation by distributing the effluent.  Anecic species have deep vertical burrows that could reduce renovation by acting as pathways of preferential flow.  Understanding the processes that effect onsite wastewater treatment is vital to designing environmentally sound systems.  The objectives of this research were to determine relative earthworm population and biomass with distance from septic system trenches and identify species present to estimate potential effects on soil renovation of household wastewaters.   I hypothesized that the earthworm population would be greater near trenches.  Earthworm populations were measured using a formalin extraction technique at five sites along three 7-meter long transects perpendicular to trenches.   The study indicated that earthworms are attracted to septic system trenches, with an average of 6.4 times more earthworms and 5.4 times more earthworm biomass within one meter of the trench than in the background in 13 out of 15 transects.  This suggests that earthworms may have a significant effect on movement of effluent.   Only epigeic and endogeic species were found in this study, therefore the potential for reduced renovation at these sites is low.  However, this may not be the case in areas with anecic earthworm populations.