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SOIL FOOD WEB
The Micro-organism - Organic Matter (MOOM) relationship is the key to
successful organic
gardening. Micro-organisms and plants have co-evolved, so it is important to
know the role micro-organisms play in our gardens.
Smart gardeners know that soil is anything but an inert substance. Healthy soil
is teeming
with life - not just earthworms and insects, but a staggering multitude of
bacteria,
fungi, and other micro-organisms. Using a microscope,one could see that a
teaspoon
of good garden soil would contain a billion bacteria, several yards of fungal
hyphae,
several thousand protozoa and a few dozen nematodes.
A great deal of the energy that results from photosynthesis in the leaves is
used by
plants to produce chemicals that are secreted through their roots. These root
exudates,
carbohydrates (sugars) and proteins, attract specific soil living bacteria and
fungi. They
in turn are eaten by bigger microbes, nematodes and protozoa, whose waste are
absorbed
by plant roots as nutrients. This natural system is the same one that has fueled
plants since they evolved. Soil life provides the nutrients needed for plant
life, and
plants initiate and fuel the cycle by producing exudates, all powered by
sunlight driven
photosynthesis. An elegant arrangement.
The term “soil food web” refers to the interactions of these organisms, which
feed on
one another and in doing so provide an environment in which plants can grow and
prosper.
When we use chemical fertilizers, we injure the microbial life that sustains
healthy
plants. The garden becomes increasingly dependent on an arsenal of artificial
substances,
such as pesticides, many of them toxic to humans as well as other forms of
life.
Pesticide use in gardens impacts many non-target organisms, such as soil based
microbes.
Thus, pesticide use must be avoided if the elegant sun driven plant growth cycle
is to remain intact. For example, there are 100,000 different species of soil
microbes in
an Old Growth Forest ecosystem. Native unaltered prairie grasslands have 60,000
species of soil microbes. 40,000 different species of soil microbes are found in
organic
garden soils but only 6,000 species of microbes are found in industrial
pesticide treated
and chemically fertilized agricultural soils.
There is an alternative to this vicious circle of loss in industrial
agricultural soils: to garden
in a way that strengthens, rather than destroys, the soil food web.
The next week we will start to explore that alternative, by examining the role
of Organic
Matter (OM) in the organic garden.
Material for this article was obtained from
www.soilfoodweb.com and “Teaming with
Microbes; A Gardener’s Guide to the Soil Food Web” by Lowenfels and Lewis.
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Sustainable
Living Through Organic Gardening