The document discusses the key components of soil, including minerals, water, air, organic matter, and microorganisms. It defines soil based on its geologic, traditional, taxonomic definitions. Soil is made up of horizons like O, A, E, B, C. Factors like parent material, climate, organisms, topography, and time affect soil formation. The document also outlines different types of soil structures and the 12 orders of soil geography.

1. Natural
Resources
Conservation
Service
Helping People Help the Land
SOIL –
The Fundamental
Concepts

2. SOIL
 Geologic definition: Loose surface of the
earth as distinguished from solid bedrock;
support of plant life not required.

3. SOIL
 Traditional definition: Material which
nourishes and supports growing plants;
includes rocks, water, snow, air.

4. SOIL COMPONENTS
 1. MINERAL - It is the largest component
of the soil and makes about 45% of the
soil. It consists of sand, silt and clay. It
retains the soils ability to retain important
nutrients.
 2. WATER- It is the second basic
component of the soil. It may vary from 2%
to 50% of the soil. It usually contains
added salts and other chemicals.

5. SOIL COMPONENTS
 3. AIR/GASES- About half of the total mass of
the soil has many cavities and holes. It makes 2
to 50% of the soil. The air found in the Earth or
soil is very different from the air found in the
atmosphere.
 4. ORGANIC AND BIOLOGICAL
COMPONENTS- It is the next basic component
found in levels of approximately 1% to 5%.It has
a very high water holding capacity and thus it
can increase the fertility of the soil.

6. SOIL COMPONENTS
 5. MICROORGANISMS-ese are found in the soil
in a very high number but covers only 1% of the
soil. These are the primary decomposers of the
raw materials present in the soil.they
eat(consume) water,air and organic matter to
recycle raw materials into humus. Other
microbes like Nitrogen fixing bacteria helps the
plants in intake of the nitrogen gas. fertility of the
soil.

7. SOIL
 Soil Taxonomy definition: Collection of natural
bodies of the earth’s surface, in places modified or even
made by man or earthy materials, containing living
matter and supporting or capable of supporting plants
out of doors.
Its upper limit is air or shallow water and its lower limit is
the depth to which soil weathering has been effective.

9.  O: The O horizon is a surface horizon that is
comprised of organic material at various
stages of decomposition. It is most prominent
in forested areas where there is the
accumulation of debris fallen from trees.
 A: The A horizon is a surface horizon that
largely consists of minerals (sand, silt, and
clay) and with appreciable amounts of organic
matter.
 E: The E horizon is a subsurface horizon that
has been heavily leached. Leaching is the
process in which soluble nutrients are lost
from the soil due to precipitation or irrigation.
Soil profile showing the
different layers or horizons.

10.  B: The B horizon is a subsurface horizon that
has accumulated from the layer(s) above. It is
a site of deposition of certain minerals that
have leached from the layer(s) above.
 C: The C horizon is a subsurface horizon. It is
the least weathered horizon. Also known as
the saprolite, it is unconsolidated, loose parent
material.
.
Soil profile showing the
different layers or horizons.

11. Factors affecting soil
formation
 physical weathering - breakdown of rocks from
the result of a mechanical action. Temperature
changes, abrasion (when rocks collide with each
other) or frost can all cause rocks to break down.
 chemical weathering - breakdown of rocks
through a change in their chemical makeup. This
can happen when the minerals within rocks react
with water, air or other chemicals.
 biological weathering - the breakdown of rocks
by living things. Burrowing animals help water and
air get into rock, and plant roots can grow into
cracks in the rock, making it split.

12. Five main interacting factors
affect the formation of soil:
 parent material - minerals forming the
basis of soil
 living organisms - influencing soil
formation
 Climate - affecting the rate of weathering
and organic decomposition
 Topography - grade of slope affecting
drainage, erosion and deposition
 Time - influencing soil properties.

13. Granular
Platy
Blocky
(Angular)
(Subangular)
Wedge
Columnar
Prismatic
Examples of Soil Structure

14. The 12 Orders of Soil
Geomorphology
 Alfisols are found in in
semiarid to moist areas.
They formed under forest or
mixed vegetative cover and
are productive for most
crops.

15. The 12 Orders of Soil
Geomorphology
 Andisols tend to be highly
productive soils. They are
common in cool areas with
moderate to high
precipitation, especially
those areas associated with
volcanic materials.

16. The 12 Orders of Soil
Geomorphology
 Aridisols are soils that are
too dry for the growth of
mesophytic plants. They
often accumulate gypsum,
salt, calcium carbonate, and
other materials that are
easily leached from soil in
more humid environments.
Aridisols are common in the
world’s deserts.

17. The 12 Orders of Soil
Geomorphology
 Entisols occur in areas of
recently deposited parent
materials or in areas where
erosion or deposition rates
are faster than the rate of
soil development; such as
dunes, steep slopes and
flood plains

18. The 12 Orders of Soil
Geomorphology
 Gelisols are soils that have
permafrost near the soil
surface, have evidence of
frost churning, or ice
segregation. These are
common in the higher
latitudes or high elevations.

19. The 12 Orders of Soil
Geomorphology
 Histosols have a high
content of organic matter
and no permafrost. Most are
saturated year round, but a
few are freely drained. They
are commonly called bogs,
moors, pears or mucks.

20. The 12 Orders of Soil
Geomorphology
 Inceptisols are soils of
semiarid to humid
environments that generally
exhibit only moderate
degrees of soil weathering
and development. These
occur in a wide variety of
climates.

21. The 12 Orders of Soil
Geomorphology
 Oxisols are highly
weathered soils of tropical
and subtropical regions.
They characteristically occur
on land surfaces that have
been stable for a long time.
They have low natural
fertility as well as a low
capacity to retain additions
of lime and fertilizer.

22. The 12 Orders of Soil
Geomorphology
 Mollisols are soils that have
a dark colored surface
horizon relatively high in
content of organic matter.
The soils are base rich
throughout and therefore are
quite fertile.

23. The 12 Orders of Soil
Geomorphology
 Vertisols have a high content
of expanding clay minerals.
They undergo pronounced
changes in volume with
changes in moisture. Because
they swell when wet, vertisols
transmit water very slowly and
have undergone little leeching.
They tend to be fairly high in
natural fertility.

24. The 12 Orders of Soil
Geomorphology
 Ultisols are soils in humid
areas. They are typically acid
soils in which most nutrients
are concentrated in the upper
few inches. They have a
moderately low capacity to
retain aditions of lime and
fertilizer.

25. The 12 Orders of Soil
Geomorphology
 Spodosols formed from
weathering processes that
strip organic matter combined
with aluminum from the
surface layer and deposit
them in the subsoil. These
tend to be acid and infertile.