Page 86 - Science Class 07

but o en found in older soils and forest Look at the different sizes of the soil par cles:
soils. v Gravel : 2.0 to 5.0 mm in diameter.

v B – (subsoil) Rich in minerals that leached
v Sand : 0.2 to 2.0 mm in diameter.
(moved down) from the A or E horizons
v Clay : Less than 0.2 mm in diameter.
and accumulated here.
On the basis of the size of the soil par cles, we
v C – (parent material) The deposit at the
earth’s surface from which the soil can categorise soil into:
developed. v Sandy Soil v Clayey Soil

v R – (bedrock) A mass of rock such as v Loamy Soil
granite, basalt, quartzite, limestone or Sandy Soil
sandstone that forms the parent material
It contains mainly sand which has gri y texture.
for some soils – if the bedrock is close
The par cles of this soil can be separated
enough to the surface to weather. This is
easily. This soil has very low or no water
not soil and is located under the C horizon.
reten on capacity. Therefore, this soil is not
good for cul va on.
Organic (Li er layer)

Topsoil

Leaching layer

Subsoil

Weathered parent material
Sandy Soil
Parent material Clayey soil

Soil Horizon As you know size of clay par cles is less than
0.2 mm. Therefore , these par cles easily form
lumps when water is added to this soil, it acts
like a hard mass. It has excellent water
1. What is soil?
reten on capacity but poor air circula on.
2. What is humus?
However, the presence of mineral contents
3. Name any four organisms found in the soil.
make it useful for plant growth.
4. What is chemical weathering?
5. What is the feature of soil found in B-horizon?
6. Why sandy soil is not good for cul va on?

TEXTURES OF SOIL
The shape and size of the soil is referred to as

texture of soil. It depends on weathering and
climate of a region.
Clayey Soil
86 Science-7