Agronomic potential of earthworms in brigalow soils of south-east Queensland

The potential of earthworms to enhance the productivity of sown pastures was investigated in the brigalow region of Qeensland where such pastures are often devoid of earthworms. Wider surveys in eastern Australia recorded 75 native or exotic earthworm species and 27 of these were screened in a series of glasshouse trials to find candidates for field introduction. Whereas some earthworm populations declined in glasshouse soil cores, a maximum increase in numbers in six months was 10-fold. Increases in yield of oats or grass test crops associated with earthworm activity were as high as 60 or 80%, while yield of grain sorghum doubled. Not all species were equally effective: a few were found to depress plant yield. However, 12 species were selected for field trials. One year after earthworm introduction to brigalow pasture, plot yields had increased by an average of 64.4%, and survivors of Aporrectodea trapezoides, Eisenia rosea, Pontoscolex corethrurus and of a native Diplotrema sp. were recovered.