Introduction to the Soil Profile and its horizonsppt

Soil profile

1. SOIL PROFILE
by
Dr. Mohan Raj C
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2. Soil profile:
The vertical section of the soil showing the various
layers from the surface to the unaffected parent
material is known as soil profile. Various layers are
known as horizons.
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3. Soil profile contains three main horizons:

Horizon A

Horizon B

Horizon C

A hypothetical mineral soil profile will include O,A,
B, C, R master horizons.
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4. 4

5. O horizon:

It is formed organic horizon. It is formed in the
upper part of mineral soil, dominated by fresh or
partly decomposed organic materials

Organic matter- 30%

Mineral fraction – clay – more than 50%
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6. 
Organic horizon are commonly seen in forest areas
and generally absent in grassland, cultivated soil in
grassland, cultivated soil.
O
1- organic horizon in which original forms of the
plant and animal residue can be recognized
through naked eye
O
2
– original forms of plant and animal residue
cannot be seen
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7. A horizon:

The surface soil or layer of soil at top which is able
to leaching and from which some soil constituent
have been removed is known as horizon A or
horizon of eluviations.

A horizon is often referred to as topsoil and is the
surface layer where organic matter accumulates.
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8. 
This layer losses clay, iron and other materials
because of leaching

The movement of organic matter, chemical
substances and mineral particles from upper horizon
of soil to the lower horizon by the downward
movement of water is called elluviation.

It is best environment for the growth of plant roots,
micro organisms and other life.
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9. B horizon:

The intermediate layer in which the materials
leached from horizon A have been redeposited is
known as horizon B or horizon of illuviation.

Horizons in which dominant features are
accumulation of clay, iron, aluminium or humus alone
or in combination.
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10. 
B horizon is often referred to as the subsoil. It is
often called zone of accumulation.

The accumulation of organic matter, chemical
substances and mineral particles in the lower
horizon as a result of downward movement of
water is called illuviation.

B horizon has less organic matter and more clay A
horizon.
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11. C horizon/substratum

It lacks the properties of A and B horizons because
it is influenced less by the soil forming process

It is usually parent material of soil
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12. 
R horizon:

The R horizon is the underlying bedrock, such as
limestone, sandstone or granite.

It is found beneath the C horizon
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13. Pedon:

The smallest unit or volume of soil that contains all
the soil horizons of a particular soil type.
Polypedon:

It is defined as a contiguous similar pedons
bounded on all sides. It is real physical soil body
which has a minimum area of more than 1 sq. Km
and an unspecified maximum area.
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