THE USE OF RESOURCE PATCHES BY EARTHWORMS

A field experiment was established to assess the effects of additional organic matter on earthworm populations. Bags of soil (15 cm deep) were placed in a pasture at Balhannah, South Australia, at the beginning of autumn 1991. The bags were initially seeded with five individuals of Aporrectodea trapezoides, and 250 g dried sheep manure was added to most bags. Manure was added either in pellet or milled form, and applied either on the surface, in the 5-10 cm layer, or evenly dispersed over 15 cm. In harvests during weeks 7, 9, and 11 after the start of the experiment, A. trapezoides and three other species, A. caliginosa, A. rosea, and Microscolex dubius, were recovered from the bags. Bags with added manure had significantly higher numbers of each species than bags with no manure. During the 4-week sampling period (weeks 7-11) the numbers of M. dubius recovered per bag decreased, while A. rosea increased. Total earthworm numbers were not influenced by either the form or the location of application of the manure. Earthworms were sampled from three depths, 0-5, 5-10, and 10-15 cm. Both numbers and biomass of earthworms were positively correlated with the location of the manure. Cocoons of Aporrectodea spp. were more abundant when the manure was milled and evenly dispersed, and were consistently located in the lower soil layers, regardless of the form or location of manure.