Construction of an Electrical Device for Sampling Earthworm Populations in the Field

Abstract

Methods for the estimation of 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 settings to suit specific environmental conditions, with control of voltage, and operation with a static or dynamic electrical field being generated. Operational ability to extract earthworms was validated in field trials in both a forested area and an agricultural field. Earthworm sampling efficiencies calculated in comparison to hand-sorting averaged around 90% for the electrical device; however, because of limited field use in this instance, these efficiencies support the general functioning of the apparatus rather than an absolute assurance of quality. 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.