Our study is a follow-up study of Clause et al. (2014), who
showed an interactive impact of soil type and earthworm species
on cast physico-chemical properties. The aim of the present study
was to disentangle the effect of seed ingestion from the effect of
earthworm casts as a germination substrate on four plant species.
Shaping artificial casts and sowing seeds in these casts has seldom
been carried out. Ingestion and passage through the earthworm
gut did not increase the germination success of seeds. Rather, it
tended to decrease the germination success of our four plant
species through the total digestion of their seeds or damages to
their seeds (O. vulgare and U. dioica), or to decrease the germination
rate of excreted seeds (F. lemanii). The presence of seeds in casts
decreased seed germination and seedling growth as compared to
control samples that were less nutrient-rich (mineral and organic).
However, effects of the passage through gut or the presence in
casts on seed germination and seedling growth were specific of
both earthworm species and of seed species