lovely professional university

1. Class – 7th
Soil types and soil profiles

2. • Take a glass tumbler three quarters filled with water.
• Add a handful of soil in glass tumbler
• Stir it well with a glass rod and leave it undisturbed for some time.
• We can see a different layers of particles of different sizes.
• The rotting dead plant and animals at it the top is humus. Below it are layers of
clay , sand and gravel.

3. • A vertical section (cutting) through soil showing different layers of soil is
called soil profile. Soil profile consists of three different layers of soil.
• HORIZONS
Each layer of soil is called a horizons. The three layers of soil in the soil profile
are
1. A-horizon(top soil)
2. B-horizon(sub soil)
3. C-horizon(sub-stratum)
4. R-horizon(parent rock)
SOIL PROFILE

4. A-horizons (top soil)
o The top layer of soil is called A- horizons.
o Top soil is dark in colour. This is because top soil is rich in minerals and
humus. The plant root grows in the top soil. The top soil contains a lot of
decayed dead plants and animal remains
o In Oher words , top soil contains a lot of humus. This humus makes the top soil
very fertile. The top soil is soft and porous and can hold water the plants need
for growth. The top soil is the most useful part of the soil.

5. B- horizons( sub-soil)
 The layers of soil which is just below the top soil is called B-horizon. It is also
known as sub-soil.
 The sub-soil is made up of slightly bigger rock particles than that of top soils.
 It is somewhat harder and more compact than the top-soils
 Sub-soil is also lighter in colour than the top-soils
 The sub-soils contains very little living organisms
 The roots of same of the tress are , however, able to reach sub soils
 The sub-soils has very little humus(decayed organic matter)
 Due to this, sub-soil is much less fertile as compared to the top-soils
 Sub-soil is rich in soluble minerals

6. C-horizon(sub-stratum)
The layers of soil which is just below the sub- soil is called c- horizon.
It is also called sub-stratum.
Sub stratum is made up of small lumps of broken rocks(or stones) formed
by the potential weathering of bed-rock (parent rock)
It has cracks running through it.
It is mostly made of rocks
Below the C-horizon we have unweathered solid rocks called bed-rock
It is this bed-rock which has produced the soil over a long period time

7. The soil is made up of six components rock particles(of different sizes),
minerals, humus (organic matter),air, water and living organism.
The rock particles present in the soil are of different sizes and chemical
composition
On the basis of their sizes , the rocks particles present in soil can be divided
mainly into four groups
1. Clay 3. Sand
2. Silt 4. Gravel

8. • The smallest rock particles present in soil from clay, because of its very small
particles , clay feels smooth to touch.
• The rock particles in soil which are a little longer than clay particles from silt.
Thus , silt is made up of rock particles somewhat bigger than that of clay. Due
to its slightly bigger sized particles, silt particles in between that of clay and
sand . The size of silt particles is bigger than that of clay particles but smaller
than those of sand particles.
• The rock particles in soil which are larger than silt particles from sand, being
quite large ,sand particles can be easily seen by us and because of its large
sized particles , sand is coarse to touch
• The largest sized rock particles present in the soil called gravel. Gravel is a kind
of tiny stones. The amount of gravel present in a good top-soil is very small

9. TYPES OF SOIL

10. There are three main types of soil. They are sandy soil, clayey soil and loamy soil
A. Sandy soil – In sandy soil the particles are large in size. They have more space between
the particles filled with air. They do not retain water and are light and dry. The soil is not
sticky and therefore these cannot be used to make pots , bricks , toys etc.
B. Clayey soil – In clayey soil the particles are smaller. They have less space between them
the particles has less air. They retain more water and heavy and wet.it is very sticky and
can be used to make bricks , toys, statues etc.
C. Loamy soil – In loamy soil the particles size is between those of sand and clay. It contains
humus and has the right water holding capacity. So it is the best soil for the growth of
plants

11. • How many layers of soil are seen in the soil profile ?
• What is soil profile ?
• How soil profile made ?
• What is the lowest layer if the soil ?
• Which soil horizon is most developed ?
• What is the colour of A-horizon?
• Which is called potters soil ?
• Which soil can retain more water ?
• Which soil has loose particles ?
• What is rocky soil called ?