Agriculture Reference
In-Depth Information
Reports by Vinceslas-Apka and Loquet (1997) and Fredrickson et al. (1997) showed that the
involvement of earthworms in a composting process to produce vermicomposts decreases the time
of stabilization of the wastes and produces an efficient organic material with nutrients and energy
reserves. Garcia et al. (1994) and Elvira et al. (1994) showed that sludges from both agri-based
industries and domestic sewage plants, which are not accepted as soil additives directly onto fields,
can be an excellent food source for vermicomposting earthworm species, with suitable organic
amendments such as plant litter or animal wastes used to produce earthworm biomass and obtain
better quality soil additives.
In the case of those earthworms used for vermicomposting of organic wastes, the relationship
between biomass production and earthworm population increase is of utmost importance. Meyer
and Bouwman (1997) provided an explanation for the possibility of not getting the population
increases they expected in these earthworms. They suggested that anisopary, which is a physiolog-
ical behavioral pattern of earthworms in which some percentage of the population remains only as
sperm donors and fails to produce cocoons, as well as various extrinsic factors such as the available
food sources and climatic factors can also contribute to changing their reproductive potential.
Similarly, the levels of hazardous heavy metals in the organic wastes fed to earthworms can affect
their spermatogenesis and spermateleosis. This was made clear in the ultrastructural studies carried
out by Reinecke and Reinecke (1997) (see
Chapter 16
, this volume), which were based on exposing
the earthworms to different concentrations of cadmium, lead, and manganese mixed with cattle
dung. These hazardous materials are taken up into earthworm tissues and may at some point enter
the upper trophic levels of the food chain, as was demonstrated in studies on earthworm populations
at a hazardous waste site (Stair et al. 1994).
In developing countries, where the current trend is to convert to more ecofriendly organic
farming, Jambhekar (1994) demonstrated improvements in the fertility status of the soil in vineyards
because of earthworms and increased yields of grapes, which is very encouraging. Similarly, Mba
(1994) highlighted the effects of vermicomposts on a ground cover crop
and
their influence in increasing earthworm activity in the soil. Encouraging the endogeic species
populations of earthworms by amending soil with organic manures and ground cover crops can
contribute significantly to soil fertility in tropical countries.
It is true that clear-cut demarcations between the role of epigeic and endogeic species of
earthworms and their limitations have to be made, as was summarized by Buckerfield (1994). If
there is any confusion, it has to be clarified by highlighting the importance of endogeic species of
earthworms and the relative inability of epigeic species of earthworm to overcome adverse physical
conditions in nature. Once this is resolved, it should be possible to designate the species of
earthworm that can work best on particular organic wastes and in particular climate conditions.
Mitchell (1997) discussed composting using epigeic earthworms to overcome organic pollution.
In most of the presentations at the Fifth International Symposium on Earthworm Ecology
(Edwards 1998),
Telfaria occidentalis
were the species chosen for vermicomposting.
Although there is information about the biology of other earthworm species like
Eisenia fetida
and
Eisenia andrei
Perionyx excavatus
or
Eudrilus eugeniae
, more is needed (Salazar et al. 1994). Fayolle et al. (1997) reported the
possibility of rearing
on organic wastes, such as horse manure and paper
sludges. Studies of the life cycle of this species on other kinds of organic wastes would increase
the number of earthworms available to use in organic waste processes. In tropical and subtropical
conditions,
Dendrobaena veneta
are the best earthworms for vermicomposting. Work is
still in progress to test the possibility of using other species from forestlands in vermicomposting.
The use of epigeic species of earthworms to combat organic pollution and produce high-quality
organic soil amendments and earthworm biomass is progressing at a slow pace in most Asian
scientific laboratories compared with workers in the United States, who have been successful in
promoting the technology of vermicomposting. Appelhof (1994) and Bisesi and Appelhof (1994)
initiated vermicomposting food waste programs in schools and have prepared worksheets and
manuals to increase interest and awareness among youngsters. White (1994) initiated the publication
E. eugeniae
and
P. excavatus
