Download Organic Matter

Organic Matter in the Soil
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Waste is a human concept. In nature
nothing is wasted, for everything is part
of a continuous cycle. Even the death of
a creature provides nutrients that will
eventually be reincorporated in the
chain of life.
Denis Hayes
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What is Organic Matter?

all plant and animal residues in the soil
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What things make up soil
organic matter?
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Plant & animal residues
Barnyard manure
Green manure
Dead roots
Insect & worm carcasses & excrement
Dead soil micro-organisms (bacteria,
fungi, protozoa)
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What is Green Manure?

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a crop grown for its organic
matter
green manure crops are generally
plowed under while they are still green
Examples = sweet clover, rye
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What two things have greatly lowered the
Organic Matter content of soil?
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soil erosion
continuous cropping
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How can organic matter be
increased?
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crop residues
barnyard manure
green manure
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What is the difference between
organic matter & humus?
Organic matter is dead plant & animal life
before it has been broken down
Humus = relative stable product of the
decomposition of organic matter
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What is Mineralization?
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organic matter is broken down into
simple mineral compounds
Due to the action of bacteria & fungi
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When organic matter breaks down,
what is released for the crop's use?

Nutrients (sulfur, nitrogen,
phosphorous, potassium, calcium,
magnesium + micronutrients)
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How does Organic Matter
Improve Soil?
1) increase water holding capacity
2) nutrients attach to O.M.
3) O.M. improves tilth (aggregate)
4) The amount of humus in soil is directly
proportional to the amount of nitrogen
in soil
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How does Organic Matter
Improve Soil?
5) Soils high in O.M. are easily worked
and may be described as having good
tilth.
6) Improves soil structure
7) Improves aeration
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Benefits of Organic Matter
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Organic Matter promotes granulation of
soil by binding soil particles into
granules.
O.M. makes clay soils less sticky and
improve tilth.
Deeper root growth and water entry
and storage are improved as well as
aeration of the soil.
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Organic Matter & Sandy Soils
•
Sandy soils have good aeration but dry
out quickly. Sandy soils increase water
holding capacity and have less erosion
as O.M. is added?
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What is the largest source of
O.M. in the soil?

plant roots
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Which is the most preferred
green manure, legumes or
non-legumes?

legumes- added nitrogen
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What is nitrogen tie-up?
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microorganisms in the soil use the
nitrogen in the soil to break down
organic matter, thus it is temporarily
"tied up" (used as food)
this is very important when considering
re-cropping and not allowing the soil to
have a year in fallow to allow for
mineralization in order to reduce the
nitrogen tie-up.
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Is organic matter a good
mulch?
Yes
1.
2.
3.
4.
Reduces surface evaporation
Equalizes soil temperature
Increases soil animal life
Reduces soil erosion
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Detrimental effects of soil
organic matter
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Energy source for many disease organisms –
ensuring their survival in the soil
Excessive amounts of plant residues are
difficult to incorporate into the soil and hinder
some planting operations
Addition of organic matter into soil may
temporarily increase the carbon:nitrogen ratio
– thus limiting the available nitrogen to the
current crop
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How many square feet are in
an acre?
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43,560
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What is an acre-six inches?
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six inches of soil over an acre
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An acre-six inches weighs how
many pounds?
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2 million
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Soil Conservation
A typical farmer is doing a "good
job" of soil conservation if he
loses less than 1/16" of topsoil
each year. How many pounds of
soil does he/she lose each year
if he/she loses 1/16"? How
many tons? (extra credit)
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How long does it take to
create soil?
It takes 100 to 400 years to
create 1" of topsoil.
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