Influence of Lumbricus terrestris inoculation on green manure disappearance and the decomposer community in a walnut orchard

Nightcrawler (Lumbricus terrestris L. [Oligochaeta: Lumbricidae]) is an ane cic earthworm typically lacking from Persian walnut (Juglans regia L.) orch ards in northern California, yet this earthworm may be established by inocu lative release. Our purpose of was to determine the effect of L. terrestris inoculation on green manure incorporation, in this case woolypod vetch (Vi cia villosa Roth ssp. varia [Host] Cabriere), and on the decomposer communi ty. Art experiment using controlled-environment microcosms showed that disa ppearance of surface-applied vetch residue was increased by the addition of L. terrestris compared to a resident earthworm complex consisting of the e ndogeic Lumbricidae Aporrectodea sp. prob. trapezoides (Duges) and Allolobo phora chlorotica (Savigny) as well as the epigeic Eisenla foetida (Savigny) . An experiment conducted in an organic Persian walnut orchard during the s pring of 1996 also showed that disappearance of surface-applied vetch resid ue was increased in plots that had been inoculated with L. terrestris. Howe ver, an additional study conducted in the same orchard during the summer of 1998 showed similar rates of vetch biomass disappearance in plots with or without inoculated L. terrestris. Colonization by L. terrestris did not lea d to significant differences in densities or live biomass for resident eart hworms in this orchard. However, night observations showed significantly gr eater densities of isopod Crustacea (Isopoda: Oniscidae) in plots without L . terrestris, suggesting possible interference between L. terrestris and th e isopods. (C) 2001 Elsevier Science Ltd. All rights reserved.