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Compost Overview
Composting
is a natural recycling process performed by micro organisms that
exist naturally in the soil. Large quantities of food, garden, lawn,
and/or farm waste can be reduced in a relatively short time to a
pile of black, crumbly humus which makes an ideal soil conditioner.
Regular
addition of compost to soil will inevitably provide benefits for the
growth of plants. The soil structure will improve, since humus
contains substances that cause aggregation of soil particles. In
clay soil this means that the microscopic individual particles will
be clumped together and more air spaces will be opened up between
clumps. Without these air spaces the clay particles stick tightly to
each other, forming a nearly impenetrable barrier to water and
gases. This is why the clay is so sticky when wet and hard when dry.
In sandy soils, the large sand particles are aggregated with humus
as well, which increases the nutrient content and moisture-holding
capacity of the sandy soil. Normally, water and nitrogen fertilizers
leach quickly from sandy soil, making it necessary to add them
frequently.
A
less
widely recognized benefit of compost lies in its humic and other
organic acids content. Humic acids bind salts, heavy metals, toxics,
pesticides, and a variety of other reactive or ionic materials,
making them unavailable for plant uptake. This translates to
healthier crops. Organic acids also improve soil physical
properties, boost trace nutrient availability through chelation, and
improve overall plant nutrition by regulating nutrient release.
These nutrients, or ions, are held by the humus particles which
contain many ion exchange sites on their surfaces. The ions are
released into soil water, and plant roots are able to take them up.
Because there are so many ion exchange sites on humus particles,
humus also increases the buffering capacity of the soil. This
condition helps to prevent rapid leaching of lime and nutrients as
well as reducing the effects of over-liming and over-fertilizing.
For
example, when a soil's pH is increased too much by adding too many
wood ashes, the most economical way to correct the condition is to
add compost, which will bind the extra basic ions that would
otherwise result in a high pH. (Compost itself is somewhat acidic
because the micro organisms responsible for “making” compost produce
organic acids in the process.)
Consistent
use of compost and other organic matter will result in dark brown or
blackish soil, which increases heat-absorbing capabilities to some
extent. Compost reduces soil erosion by holding water so it can
percolate into lower soil layers rather than run off, carrying soil
particles with it. Compost also reduces crusting of the soil surface
by slowing evaporation. Compost provides nutrition for earthworms,
soil insects, and micro organisms, many of which will help balance
the populations of less desirable soil fauna over time.
Mycorrhizal
fungi, which have been proven to benefit plants through their
association with plant roots, are also prolific in high humus soil.
Finally,
the products of the composting process contain common nutrient
elements (Nitrogen, Phosphorous, Potassium, Magnesium, etc.) found
in synthetic fertilizers, as well as many trace elements not
available from commonly used synthetic fertilizers.
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