Impact of tillage practices and burrows of a native Australian anecic earthworm on soil hydrology

Anecic earthworms are rare in Australian soils and potential benefits of introduction of exotic anecic earthworms have been suggested. The contribution of the native anecic earthworms to soil hydrology is unknown. The impact of tillage on the abundance and continuity of burrows formed by the native earthworm, Spenceriella hamiltoni (Fletcher) and consequent effect on hydrology were investigated in a red earth (Ultisol) in the Central Tablelands of New South Wales, Australia. On the permanent pasture site, the burrows occurred at a density of 157 (+/-65) m(-2), had an average diameter of 6.0 mm (S.D. = 1.6), and a predicated median length of 1.8 m. Dye infiltration studies showed that only 53% of the burrow openings were conducting and therefore available for infiltration under high rainfall conditions. It was estimated that a single burrow over an area of one square metre had an infiltration rate of 1.9 times that of the soil matrix (6.7 mm h(-1) versus 3.6 mm h(-1)). Prediction using the rainfall characteristics of the region and the existing density of transmitting burrows under permanent pasture suggests that runoff should be a rare event (