Page 96 - Science class 4

LAYERS OF SOIL

There are three layers in the soil. These are :
1. Topsoil 2. Subsoil 3. Bedrock

Topsoil is a dark coloured layer at the top of the soil. It is fertile and suitable for

plants to grow. It mainly contains humus and fine particles of soil.
Just below the topsoil, there is a layer of light-coloured soil called subsoil. It is

not suitable for growing plants.
The bottom layer of the soil is called bedrock . It consists of hard solid rocks.

Strange But True

Natural processes can take more than 500 years to form 2 centimetres of
topsoil.

LIFE
LIFE
LIFE IN THE SOILIN THE SOILIN THE SOIL
Animals like rats and earthworms make burrows
in the soil. While digging burrows in the soil, they

break the harder parts of the soil. This makes the

soil soft. Plants tend to grow well in soft soils
because water easily enters the soil through the

burrows. The excretion of animals make the soil
fertile.

Microorganisms like bacteria present in the soil fix

the atmospheric nitrogen in the soil.

TYPES OF SOIL

There are four types of soil, depending on the

size, feel and colour of the soil particles.

1. Gravel soil
Gravel is made up of rock pieces. It does not

hold water. It is used for laying roads.

2. Sandy soil
Sandy soil is light and contains a little quantity

of organic matter. It holds very little water. It
gets carried away by the wind.