Soil compaction is a problem of modern agriculture, caused by heavy machine
ry when used in unsuitable, especially moist, conditions. Some regeneration
processes in compacted loess soil were studied in a field experiment near
Relliehausen, at the edge of the Selling mountains in Lower Saxony, Germany
. Conventional tillage (CT) and conservation tillage (CS) systems were comp
ared. The compaction was induced by the use of different wheel loads. The i
nfluence of earthworms was determined by comparing soil aggregates and cast
s with respect to dry and moist porosity, swelling, and water stable aggreg
ation. For visualisation of the microstructure, a scanning electron microsc
ope was used. The casts were obtained from two earthworm species living for
6 months in the laboratory in monoliths, taken on the plots after the whee
ling procedure. The casts showed 10-20% higher values for porosity and abou
t 50% higher swelling values than comparable soil aggregates, while the rel
ative water stability was ca. 10% lower. We conclude that casts are looser
and less stable than aggregates from the soil the earthworms ingested. To s
how the ecological relevance of the changes in the casts, the cast producti
on per hectare per year was calculated. It was especially high in the most
loaded soil under CS with endogeic species.