The impact of organic matter amendments and activity of
earthworms on carbon storage and biogeochemical parameters
was studied in a tropical soil amended with compost or vermicompost.
Sustained increase of OC storage was dependent on the
nature of the organic amendment. Whereas compost amendment
may lead to sustained increase of SOME contents, vermicompost
may be more accessible to the soil microbial biomass. Therefore,
our study suggests that compost would appear as a better candidate
for improving OC sequestration in soil. However, it is worth
noting that, due to its better availability, crop yields were greater
with vermicompost treatment.
The presence of earthworms decreased carbon storage in soils
amended with organic materials. Highest decrease was observed in
the vermicompost treatment. Moreover, earthworm activity may
also lead to some extent to protection of OM in soil aggregates as
illustrated by positive correlation of earthworm treatments with
less degraded lignin signatures. The relationship between the OM
changes induced by earthworms and soil functions yet needs to be
elucidated.