Influence of earthworms, Aporrectodea spp. (Lumbricidae), on lime burial in pasture soils in south-eastern Australia

The relative abilities of 3 exotic lumbricid earthworms, the endogeic Aporr ectodea caliginosa and A. trapezoides and the anecic A. longa, to bury surf ace-applied lime and help ameliorate soil acidity were measured in cages in 7 pasture soils in south-eastern Australia. All 3 species buried lime, mos tly within the top 5 cm of the soil profile, but A. longa buried it deeper than A. caliginosa and A. trapezoides. A. longa significantly increased soi l pH at 15-20 cm depth at some sites within 5 months (winter-spring, the ea rthworm 'season' in the Mediterranean climate of south-eastern Australia). Lime burial varied markedly between sites. These site differences were expl ained, at least in part, by variations in rainfall. Lime burial increased w ith earthworm density. A minimum density of 214 A. longa/m(2) was needed to significantly enhance lime burial within one season. Higher densities were required for the other two species. However, per unit of biomass, A. calig inosa and A. trapezoides were generally more able to bury lime in the upper soil layers (2.5-10 cm depth) than A. longa. Agricultural soils in south-e astern Australia are dominated by shallow burrowing species such as A. cali ginosa and A. trapezoides. Deeper burrowers such as A. longa are rare. Intr oduction of A. longa to soils in high-rainfall regions of south-eastern Aus tralia, where it does not presently occur, should enhance lime burial and h elp reduce soil acidity.