I have expertise in making educational and other PPTs. Email me for more PPTs at a very reasonable price that perfectly fits in your budget. Email: parmarshivam105@gmail.com Chapter - 9, Soil, Science, Class 7 SOIL SOIL FORMATION TYPES OF WEATHERING PHYSICAL WEATHERING CHEMICAL WEATHERING BIOLOGICAL WEATHERING HUMUS SOIL PROFILE HORIZON FACTORS AFFECTING SOIL FORMATION COMPOSITION OF SOIL PROPERTIES OF SOIL TYPES OF SOIL SANDY SOIL CLAYEY SOIL LOAMY SOIL PERCOLATION RATE OF SOIL SOIL EROSION SOIL POLLUTION CAUSES OF SOIL POLLUTION pH AND AIR CONTENT OF SOIL MOISTURE PRESENT IN SOIL ABSORPTION OF WATER BY SOIL CROPS Every topic of this chapter is well written concisely and visuals will help you in understanding and imagining the practicality of all the topics. By Shivam Parmar (Entrepreneur)

1. By Shivam Parmar
(Entrepreneur)
Chapter - 9
Soil
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2. SOIL
• It forms the upper
surface of the earth
where life thrives and is
the base of all
agriculture.
• Due to the physical and
chemical weathering of
rocks, it comprises of
minerals and gravel,
microbes, insects,
decaying organic matter
(humus), nutrients,
water and air.

3. SOIL FORMATION
• Soil is the uppermost layer
of the Earth's surface. It is
formed by the breakdown
of rocks over thousands of
years by a process called
weathering.
• Weathering is the process
of breaking down rocks into
smaller particles by the
action of wind and water,
change in temperature and
penetrating roots of plants.

5. TYPES OF
WEATHERING
• Physical weathering
• Chemical weathering
• Biological weathering

6. PHYSICAL
WEATHERING
The breaking down of
big rocks into smaller
sized rock particles with
the help of agents like
wind, water or change in
temperature is called
physical weathering.

7. CHEMICAL WEATHERING
• Chemical weathering
changes the chemical
nature of the soil.
• When rain water mixed
with gases like carbon
dioxide, Sulphur dioxide
and nitrogen oxides in the
atmosphere it forms acid
rain.
• When acid rain falls on the
surface of the Earth it
makes the soil slightly
acidic.

9. BIOLOGICAL
WEATHERING
• The roots of trees
and borrowing of
animals inside the
soil bring about this
type of weathering.
• Roots of trees and
plants grow through
the rocks contribute
to weathering.

11. HUMUS
• Humus is the organic
component present in
the soil formed by the
decomposition of plant
materials by
microorganisms
present in the soil.
• Humus is the rotting
dead matter in the soil.

12. SOIL PROFILE
• The soil profile is a
composition of
different layers of soil
in a vertical section.
• Each layer is different
from others because
of its texture, colour,
depth and chemical
composition.

13. HORIZON
Each layer in a soil profile is
defined as a horizon.
A - horizon or topsoil is the
soft, porous layer which can
absorb and hold more water.
B - horizon or middle layer is
the more compact and
harder layer.
C - horizon is the third layer
made up of small rocks.
D - Bedrock is the fourth and
hardest layer.

14. FACTORS
AFFECTING
SOIL
FORMATION
• Climate: Climate conditions like harsh
wind, rainfall and fluctuating temperature
leads to the formation of cracks in the
rocks.
• Landscape: The landscape in the hills
facilitate the running down of
water, thereby eroding the rocks with
more intensity and causing them to break
or crack.
• Nature of the parent rock: Soil formed will
have similar composition as that of the
parent rock. For instance, if the parent
rock has high calcium content the soil
formed will also be rich in calcium.

15. COMPOSITION OF SOIL
Soil has four main components:
• Parent material (clay, sand or
gravel)
• Water
• Air (present in the spaces
between the soil particles)
• organic matter (humus)

16. PROPERTIES OF SOIL
Absorption: The ability of a
particular type of soil to
absorb and retain water is
called its water- holding
capacity.
Pore space: Soil has spaces
between its particles known
as pore spaces. Pore space is
a very important property of
soil.
Percolation rate: Percolation
means the movement of
water through the soil.
Percolation rate is the rate or
speed at which water flows
through the pores in the soil.

17. TYPES
OF
SOIL
• Soils are of different type
because of their water
absorbing capacity.
• This is because of the
differences in the size of
particles in each type of soil.

18. SANDY SOIL
• Contains large coarse
particles which we call
send.
• Sand grains form large
spaces between the
particles which makes
sandy soil very porous and
cannot hold water for
long.
• This soil is mainly found in
places with warm climates
such as deserts and
marshy areas.

19. CLAYEY SOIL
• The clayey soil consists
of a larger proportion of
finer particles. Clay soils
contain more than 30
percent fine clay
particles.
• Clays swell and shrink as
they wet and dry,
effectively cultivating
themselves.

20. LOAMY SOIL
• When the proportion
of larger and finer
particles are equal,
then that type of soil is
called as loamy soil.
• Loamy soil is a mixture
of silt, clay and sand
which is the best
topsoil for growing
plants.

21. PERCOLATION
RATE OF SOIL
• Percolation rate of soil is
used to determine the
absorption rate of the
soil.
• The rate of percolation is
the ratio of the amount
of water in millimetres
to the percolation time
in minutes.

22. SOIL EROSION
The process of removal of
land by water, wind or ice
is known as erosion. The
process of removal of soil
by wind and water in the
absence of plants is called
as soil erosion.
Methods to prevent soil
erosion are:
• Deforestation should be
avoided.
• Plant more trees.

23. SOIL POLLUTION
Soil pollution is the
presence of unwanted
substances in the soil
that can be harmful for
all living beings.

24. CAUSES OF
SOIL POLLUTION
• Solid waste (human
excreta, fruits and
vegetable peels, plastics,
metal objects, etc.),excess
use of chemicals such as
fertilizers and acid rain are
the main contributors to
soil pollution.
• Untreated sewage sludge,
human excreta, livestock,
etc., used as manure also
contributors to soil
pollution.

25. pH AND AIR CONTENT OF SOIL
Soils can have different pH
depending upon their acidic, basic
or neutral nature. Based upon the
pH different types of crops grow
in the soil.
Soil is made up of particles of
different sizes these particles can
be loosely bound or tightly bound.
The air often occupies the space
in between these particles. This
allows life to sustain in the soil
such as microorganisms.

26. MOISTURE
PRESENT IN SOIL
• Moisture is soil is the
amount of water present in
the soil.
• Moisture in the soil can be
removed by setting up the
following experiment.
• Take soil samples and put it
in a boiling tube and heat it,
we can observe water drops
in the mouth of the
test tube. This way we can
remove moisture in the soil.

27. ABSORPTION OF
WATER BY SOIL
The amount of water absorbed
by the soil when water is
poured into the soil is called
absorption capacity or
absorption of water by soil.

28. CROPS
• Depending on the climatic
factors and components of
the soil different types of
crops are grown in different
regions.
• Clayey soil and loamy soil –
Good for growing
cereals like wheat and
gram.
• Clayey soil, soils rich in
organic matter and soils
with good capacity to retain
water – Good for growing
paddy, wheat.

29. Thank You
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