Understanding Microbial Activity
of an energy source. Adding a composted material to the soil
Repeat the above experiment,
will not stimulate increased microbial activity since composts
replacing the mineral nitrogen
are the end product of microbial decomposition devoid
source with an organic nitrogen
of substances that would serve as an energy source.
source at the same total nitroInoculating a rooting medium with either
gen application rate, and
bacteria or fungi, or a mixture of both, will
there will be little microbial
not create microbial activity, unless the
activity as microbes require
rooting medium contains an energy
a soluble nitrogen source
source. There is also what is
to function. It could be that
known as an intensity factor that
even over an extended period
needs to be taken into considof time, the organic nitrogeneration when adding compost,
containing substance may
a composted material to the
energy source or inoculum to
not be easily decomposed
a rooting medium in terms of
since the level of microbial
soil will not stimulate increased
what already exists and what
activity is low due to nitromicrobial activity since composts
is being added, for it is the
gen deficiency. However, if
intensity added that deterthere is some mineral form
are the end product of microbial
mines the effect.
of nitrogen in the organic
decomposition, devoid of
All micro-organisms in a
substance, microbial activity
rooting medium are competing
will occur, and depending on
substances that would serve as
for the same essential nutrient
the level of activity, decomposian energy source.”
elements as the plant, so their
tion of the organic substance will
active presence can result in
begin to occur, the extent dependa plant nutrient element
ing on the quantity of the energy
deficiency. A good illustrasource and available nitrogen.
tive example is what can
Such studies need to be conducted to
happen when wheat straw
determine what level of microbial activity
is plowed under followed by
does occur if the source of an essential plant
the planting of corn with a
nutrient element, particularly nitrogen, is as
high nitrogen requirement. The
an organic form. In addition, the level of microwheat straw becomes an energy
bial activity in a rooting medium is determined by
source for soil micro-organisms,
the available energy supply necessary for the microwhich will then absorb much, if not all,
organisms to function and multiply. When plants are
of the available nitrogen from the soil,
being grown in a rooting medium, the root itself can be the
leaving little for the emerging corn plants.
source for energy substances, which then gives rise to what
The result can be a severe nitrogen deficiency. Therefore,
is referred to as the rhizosphere, a narrow cylindrical zone
farmers are advised to add a fertilizer source of nitrogen, sufaround the plant root where there exists an active microbial
ficient to provide adequate nitrogen for both the corn plants
population. This is not the case in the whole soil, which
and micro-organisms.
might be essentially sterile by comparison because of the lack
Adding
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Maximum Yield USA | February 2014