Appraisal of the electrical octet method for estimating earthworm populations in arable land

Quantitative methods are needed for the assessment of the size and composit ion of earthworm communities. A poorly documented electrical sampling metho d, Thielemann's octet method, was compared with two long-established method s, formalin extraction and soil hand sorting, in conventional and direct-dr illed wheat cropping systems at two sites with medium to heavy textured soi ls in Ireland. Under all agronomic conditions tested, the electrical method extracted significantly higher earthworm numbers than formalin, but earthw orm biomasses were not significantly different. When used routinely over tw o years during periods of high earthworm activity, the electrical method yi elded community estimates that were comparable in both size and species com position to those obtained by soil hand sorting (25 cm depth), except in re cently ploughed land. However, Murchieona minuscula, a minute endogeic spec ies, was underestimated by electrical extraction. It is concluded that the electrical octet method can be a reliable and useful alternative to other d ynamic methods for estimating earthworm populations, especially in situatio ns where minimum soil disturbance is desirable.