CAST PRODUCTION AND SOIL TURNOVER BY EARTHWORMS IN SOIL CORES FROM SOUTH AUSTRALIAN PASTURES

Rates of cast production by Aporrectodea spp. in undisturbed soil core s taken from red-brown podzolic pasture soils in South Australia were measured in the laboratory at 15 degrees C. Aporrectodea caliginosa an d A. trapezoides were already present at a biomass of c. 1 g per core, and three immature A. longa specimens (c. 3 g biomass) were added to each core. The mean daily rate of cast deposition on the surface of th e cores over a 24 day period was 0.5 g dry soil per g earthworm biomas s, and this represented 62-85% of total soil egestion by the earthworm s. This high rate of surface cast production was attributed to the pre sence of A. longa, and it is concluded that successful establishment o f this species-could greatly accelerate rates of soil turnover and lim e and fertilizer incorporation in South Australian pastures.