Effect of Hormogaster elisae (Oligochaeta; Hormogastridae) on the stability of soil aggregates

The production and stability of soil aggregates produced by laboratory cultures of the endogeic earthworm Hormogaster elisae was studied using three different techniques: the determination of the soil mean weight diameter (MWD), the aggregate tensile strength, and by the Blanchart method, which involves three different tests. The MWD index of soils was higher in microcosms containing H. elisae. Tensile strength was significantly higher in earthworm casts than in naturally formed aggregates. The Blanchart method also showed aggregates produced by earthworms to be more stable. The results of all three methods concur in that aggregates produced by H. elisae are larger and more stable than those produced in control microcosms without earthworms.