Method for caging earthworms for use in field experiments

A method is described for caging earthworms in undisturbed soil in field experiments. The method is applicable to sites which are seasonally dry (e.g. summer in southern Australia). Cages were made from sections of PVC pipe (20 cm long × 30 cm dia) which were driven vertically into the soil beneath a permanent pasture in South Australia during spring when the soil was moist and resident earthworms were active near the surface. During the following summer, when most resident earthworms had burrowed below the depth of the pipes to escape surface aridity, the pipes and the soil within them were lifted from the surrounding soil. Fine curtain mesh was strapped across the bottom edges of the pipes and the resultant “cages” were then replaced in their holes. The mesh isolated the soil within the cages and prevented escape or invasion of earthworms during the subsequent wet season when the desired earthworm species were added. The method was used to compare: (1) the influences of surface-applied lime and sheep dung on the establishment of two earthworm species, Aporrectodea longa (Lumbricidae) and Spenceriella sp. (Megascolecidae); (2) the abilities of the same two earthworm species to bury lime and dung; and (3) the relative influences of A. caliginosa, A. longa, A. rosea, A. trapezoides and Spenceriella sp. on pasture production. The earthworms were caged for 5 months. Survivorship of all species was good (⩾ 50%). Contamination in the cages by undesired species was small (<20%). The addition of sheep dung enhanced the establishment of A. longa (greater numbers and biomass) but not the establishment of Spenceriella sp. The addition of lime did not influence the establishment of either A. longa or Spenceriella sp. A. longa buried lime and dung more readily than did Spenceriella sp. Pasture production was greater in the presence of A. longa and dung than in other treatments.