Page 103 - ACTIVE SCIENCE 4 TOC

S oil Profile
Soil profile refers to the different layers of soil. There are three main layers in soil.

1. Topsoil 2. Subsoil 3. Bedrock

1. Topsoil : It is the uppermost layer which lies between 2-8 inches from the
surface. It is rich in humus, air, water and microorganisms which are very
good for the growth of plants. It has fine particles like sand and clay.

2. Subsoil : It lies under the topsoil and contains
sand, silt and clay. However, this layer has less
organic matter or humus which makes it less
fertile in comparison to the topsoil. It also has Topsoil
broken pieces of rocks making it very compact.
It does not contain much air but holds water. It Subsoil
is light in colour.
Bedrock
3. Bedrock : The lowest layer at the bottom
of the soil profile is called the bedrock. It has
large hard pieces of rocks and can extend to Parent rock
hundreds of metres under the earth’s surface. It
has unweathered rocks. It cannot contain much
water.
Soil Profile
Soil profile varies from place to place and is greatly
affected by the climate of an area.

S oil Erosion
The process of loss of top fertile layer of soil by
the action of wind, running water, animals and
human activities is called soil erosion. It spoils
the soil quality capacity to grone plants and
hold water. Various other factors such as heavy

rainfall, overgrazing by animals, deforestation,
landslides, flooding and construction by human

beings can lead to soil erosion. Soil Erosion

S oil Conservation
The humus and microorganisms contained in the topsoil need to be replenished to

maintain soil quality. Therefore, we should take steps to conserve soil. The process
of prevention of soil erosion is called soil conservation.

110 Active Science-4