Earthworms : Ecology and Impact on Agronomic Soils

Research suggests that earthworm activities in no-till soil profiles will increase water infiltration capacity and improve soil fertility. A three part study was conducted from 1990 to 1993. First, surveys were conducted to determine earthworm ecology and population density at several sites in South Dakota. Six earthworm species were identified in the survey. Population densities ranged from 0 to 191 earthworms m-2. The greatest earthworm populations were found in fertile soils of medium texture with little or no disturbance. Second, the impact of earthworm activity on soil water infiltration capacity was measured in worm and no-worm soil treatments using double ring and sprinkler infiltrometers. Water infiltration capacity was higher in some of the worm treatments compared to the no-worm treatments. The greatest difference between treatments was found in soils under long-term no-till farming practice. Third, earthworms (Lumbricus terresris) were introduced (planted) into earthworm void farm ground to evaluate their survivability and population movement. The average population estimate was six earthworms m-2 after two years with an average population movement of 2.5 to 5 meters per year