Abstract
We bred the earthworm Eisenia foetida (Savigny) in the laboratory for ten months to examine soil generation in nutrient-poor volcanic ash deposited by the 1977-78 eruptions of the Mt. Usu volcano, with the addition of plant litter. The earthworms promoted the activity of soil microbes, and a cast layer was easily formed. The particles were significantly more fine-grained and aggregated than in the control, and the water-holding capacity rose significantly. Inorganic nitrogen increased ten fold compared with the control, and the available phosphorous and exchangeable cations (Ca2+, Mg2+, K+, Na+) also increased significantly. The results suggest the possibility of hastening the recovery of vegetation on volcanic ash by utilizing the activity of earthworms.
