Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2008
Publication Date: 7/1/2008
Citation: Lachnicht Weyers, S.L., Schomberg, H.H., Hendrix, P.F., Spokas, K.A., Endale, D.M. 2008. Construction of an electrical device for sampling earthworm populations in the field. Applied Engineering in Agriculture. 24(3):391-397.
Interpretive Summary: Earthworm populations are important parameters for measuring soil quality; however, effective sampling methodologies need to be established that will allow for population estimates in conservation systems where soil disturbance is of concern. An electrical device for sampling earthworm populations was constructed and the operational design was disseminated through this work. The efficiency of the device to sample earthworm populations was tested in a forested area and found to be 75%-100% effective, depending on soil conditions, earthworm species present and their stage of growth. The device was used successfully in a conservation system experiment, and established that earthworm populations in no-tillage operations with application of poultry manure were greater than in conventional systems of tillage and fertilizer use. The greater earthworm population indicates a positive impact of conservation management on soil quality. Scientists, producers, soil quality consultants and others will benefit from the availability of a design plan for sampling earthworms. Thus, they will be able to assemble greater evidence of the positive impact on soil quality that conservation management systems can offer without the labor intensive and destructive sampling efforts previously required to estimate earthworm populations.
Technical Abstract: Well-known methods for estimating earthworm population densities range from laborious handsorting through chemical applications to electrical extraction. Of these methods, only the electrical extraction allows for sampling of earthworms without detrimental soil disturbance or contamination. However, a device to extract earthworms under controlled, electronic conditions is not readily available to researchers. An improved design on the long-established electrical "octet" extraction device is presented. This improved design allows for hand-built construction of an apparatus that can be connected to external drive controls, including data loggers and PC-controlled drivers. This design also allows for modification of sampling procedures to suit specific environmental conditions, with control of voltage, and operation with generation of a static or dynamic electrical field. Operational ability to extract earthworms was validated in field trials in a forested area and an agricultural field. Earthworm sampling efficiencies of 75% to 100% were calculated in comparison to handsorting. In using this hand-built device, we established that this design is capable of extracting both native and exotic earthworms of various age and size class under various soil conditions, that soil disturbance and contamination can be avoided, and that the device can easily be transported into remote locations.