Soil is formed from the weathering of underlying rock and organic material from dead plants and animals. It is composed of various horizons with organic material concentrated near the surface. The O horizon contains freshly fallen plant material while the A horizon contains more decomposed organic matter mixed with minerals. Deeper horizons like the B contain fewer organics that have been further broken down. The C horizon is mostly unchanged parent material. Soil quality indicates environmental quality as soil is essential for plant growth and supports many ecosystem processes. Maintaining soil quality through sustainable land management practices is important for long term agricultural productivity and environmental sustainability.

1. SOIL:
Organizing
Component for
Terrestrial Ecosystem

2. Atmosphere Hydrosphere Pedosphere
ECOSPHERE

3. SOIL
The net result of the action of climate
and organisms, especially vegetation
and microbes, on the parent material
of the surface of the Earth.
It is composed of a parent material –
the underlying geological or mineral
substrate – and an organic
component in which organisms and
their products intermingled with the
finely divided and modified parent
material.

4. SOIL HORIZONSOIL PROFILE

5. O Horizon
O Horizon is generally only
a few centimeters thick,
consists of organic matter.
The remains of the plant
materials are clearly
recognizable in the upper
part of the O Horizon, but its
lower part consists of
humus.

6. A Horizon (Top Soil)
A Horizon is composed
of the bodies of plants
and animals that are
being reduced to finely
divided organic material
by humification.

7. Litter
Humus
Leached zone
Leaf mold

8. A-0 Horizon
The litter represents the detritus
component and can be considered a
sort of ecological subsystem in which
microorganisms (bacteria and fungi)
work in partnership with small
arthropods (soil mites and
collembolans) to decompose the
organic material.

9. B Horizon
B Horizon is composed of
mineral soil in which the
organic compounds have
been converted by
decomposers into organic
compounds (mineralization)
and thoroughly mixed with
divided parent material.

10. B Horizon
The soluble materials of the
B horizon are often formed
in the A horizon and
deposited or leached by the
downward flow of water into
the B horizon.

11. C Horizon
C Horizon is the more or less
unmodified parent material.
This parent material may
represent the original mineral
formation that is disintegrating
in place, or it may have been
transported to the site by
gravity, water, glaciers, or
wind.

12. The soil profile and the relative
thickness of the horizons are
generally characterized by :
• Climatic Regions
• Topographical Situations
SOIL

13. 3 Important Attributes to be
measured in the A and B Horizons:
1. Texture
2. Percentage of Organic Matter
3. Exchange Capacity
SOIL

14. Soil erosion caused by water and
wind occurs naturally at low rates all
the time resulting from great floods,
glaciers, volcanic eruptions, and
other episodic events.
SOIL Displacement:
Natural and Human-Accelerated
Areas that lose soil faster than the
new soil is formed generally suffer
reduced productivity and other
detrimental effects.
Areas receiving too much soil may
also be negatively affected. However,
fertility may be enhanced when soils
are washed down from hills into river
valleys and deltas or are deposited
on prairies by winds.
As is the case for so many natural
processes, humans tend to
accelerate soil erosion, often to our
long-term detriment.

15. SOIL Quality:
Indicator of Environmental Quality
In the closing years of the 20th century,
scientific attention and publicity on high-
yielding crop varieties diverted attention
from the fact that maintaining high yields
depends on maintaining soil quality,
which, in turn, depends on sustainable
tillage and diversity both at the crop and
landscape levels.
As soil is the chief organizing center foe
terrestrial and wetland ecosystems, soil
quality should be a good indicator of
environmental quality in general. In other
words, if the quality of the soil is being
maintained, then whatever is going on to
the landscape, whether natural or
managed, should be sustained.