The aim of this study was to determine the influence of compost and vermicompost produced from
buffalo manure on soil bacterial diversity and activity in the presence and absence of the endogeic
earthworm Metaphire posthuma. This experiment was carried out for 15 months with a maizeetomato
emaize cycle under greenhouse conditions in Northern Vietnam. It showed a positive influence of
compost and vermicompost on soil microbial properties, with higher cultivable bacteria, higher bacterial
and catabolic diversity (Shannon diversity ‘H’ and Richness ‘S’) indices and higher enzymatic activities
than control soils which only received mineral fertilizers. Differences also occurred between compost
and vermicompost with lower activity and diversity in the soil amended with vermicompost, probably
because of its higher molecular stability. The presence of M. posthuma led to divergent dynamics of
bacterial community in soils amended with compost and vermicompost. Earthworms negatively influenced
soil microbial properties in composted soil (lower Average Well Color Development ‘AWCD’),
probably because of competition between bacteria and earthworms for organic resources and/or because
of the consumption of microbes by earthworms. Conversely, the presence of earthworms increased
bacterial diversity and activity with higher AWCD, and H and S indices for the vermicompost treatment,
probably as a result of a stimulation of microorganisms that allow the degradation of stable organic
matter and its further consumption by earthworms. In conclusion, this study clearly confirmed the
different impacts of compost and vermicompost on bacterial activity and diversity and highlighted the
importance considering the interaction of these organic substrates with local endogeic earthworms