The Eco-Logic of Vermiculture

Earthworms and Bacteria Enjoy a Symbiotic Relationship

By Uday Bhawalker

Each
organism has a role and occupies a niche. In fact, shown by the Russian
ecologist, Gause, about 30 years ago that each niche has only one
organism with its specific food. If another organism is introduced, it
either gets wiped out or creates its own micro-niche by living
symbiotically with the first, for example, by using the waste matter of
the first organism as food.

Ecology of worm bins

Let us
use eco-logic to understand the ecology (ecology: the relationship
between organisms and their environment) of worm bins. Worm bins are
meant for bioprocessing of organic wastes. In a worm bin organics are
consumed by diverse organisms and those who are fast out-compete those
who are slow.

It is a fact of life that small organisms such as
bacteria are voracious eaters. Their appetite could be 20,000 times
that of a man when compared on equal weight basis. Next in size come
the fungi. Fungi have smaller appetites since they have about 100 times
larger body size and anaerobic bacteria have poor appetites due to the
unavailability of oxygen. All the other large organisms (worms and
humans included) have smaller appetites relative to their weight.

What
then prevents the bacteria from out-competing the larger animals for
the available food? If bacteria, fungi, and worms are competing for
food in a worm bin, obviously bacteria would win due to their speed of
food consumption and growth. Given ideal conditions of temperature,
moisture, pH and aeration, bacteria can double their population in 20
minutes, fungi in 3-4 hours, while worms take days. This speed of
reproduction coupled with their voracious appetite mentioned above make
beneficial bacteria the clear winner if conditions are suitable for
them.

Beneficial bacteria in the composting process prefer a
neutral pH and about 50% moisture which allows good aeration in the
mass of decomposing organics. Fungi come into play only when bacteria
slow down due to low moisture or acidity. Stale bread, for example,
would develop fungal growth when the moisture level is too low for
bacteria. Composting starts with bacteria but it will soon change over
to fungal mode due to the acidity produced by the bacteria. If this
acidity (normally produced in the process of decomposition) is coupled
with higher moisture content (above 75%) the process becomes suitable
for redworms and they will become the dominant processors.

Thus,
redworms have a role when the pH becomes acidic and bacteria slow down
their activity. It is found that redworms grow faster and eat fastest
when the pH is around 5. Redworms consume the acidic food and produce
alkaline excretions, thus shifting the pH to neutral, which is more
suitable for bacteria. Once the wastes that are creating the acidity
have been consumed by the redworms their population will diminish as
their job is completed and the environment will be less suitable for
them.

The role of burrowing earthworms on the other hand is one
which is played symbiotically with beneficial bacteria, as they both
prefer the conditions of neutral pH and 50% moisture. And, since in its
role as a soil processor, the earthworm ingests these bacteria, the gut
of the earthworm is a perfect natural bioreactor which provides an
ideal breeding ground for these beneficial aerobic bacteria while at
the same time destroying anaerobic bacteria, fungi and pathogens.

Although
this process utilizing burrowing earthworms can be carried out most
simply and efficiently directly on the soil, it is also possible to
have a worm bin with earthworms in it as long as there is 3-4 inches of
soil as bedding and a neutral pH and a 50% moisture content are
maintained. A neutral pH is maintained in part through the use of rock
dust, which is added each time food wastes are introduced to the system.

Nature’s warning signals

When
organics are processed around neutral pH and create no odor, the
process is hygienic. Bacteria that grow at neutral pH are mostly
beneficial soil bacteria that produce several growth factors that are
needed by plants. Safe processing of organics takes place without
emitting signals such as odor and pests.

When the pH becomes too
acidic or alkaline or the organics become anaerobic due to a shortage
of oxygen, the organics may be processed by pathogens and
toxin-producing bacteria. This amounts to a kind of biological fire
(biofire). Such biofire is sensed, alarmed and remediated by pests such
as rats, flies, etc. They provide us with a visible sign that warns of
an unhealthy situation.

So if your worm bin attracts pests, they
are probably involved in a fire-fighting service. We can help them by
sprinkling lime or fine rock dust on the composting mass, which will
return the pH to neutral and encourage speedier processing of the
organics into excellent pant food. When the job is being well done, it
displays no warning signals.

This summation of Uday
Bhawalker’s work to the present date has been compiled by him in a
380-page treatise which he has entitled Vermiculture Ecotechnology. For
current information, please visit www.wormdigest.org.

Reprinted from Worm Digest, Winter 1995.


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