NCERT Class VII Science Solutions: Chapter 9 – Soil Part 3

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Question 6:

List the differences between clayey soil and sandy soil.

Answer:

Difference between claly and sandy soil

S. No.

Clayey soil

Sandy soil

1.

Ratio of fine particles is higher.

Ratio of large particles is higher.

2.

Soil retains water and becomes sticky and wet.

Loose particles, air permeate through the soil.

3.

Suitable for crops like paddy, wheat and gram.

Suitable for vegetables, peanuts and cotton cultivation.

4.

Difficult to plough when wet.

Dries up easily. Cannot retain water.

As showing in images is a clayey soil and sandy soil

Clayey Soil and Sandy Soil

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Question 7:

Sketch the cross section of soil and label the various layers.

Answer:

A vertical section through different layers of the soil is called the soil profile. Each layer differs in feel (texture), colour, depth and chemical composition. These layers are referred to as horizons.

  • The uppermost horizon is generally dark in colour as it is rich in humus and minerals. The humus makes the soil fertile and provides nutrients to growing plants. This layer is generally soft, porous and can retain more water. It is called the topsoil or the A-horizon.

  • The next layer has a lesser amount of humus but more of minerals. This layer is generally harder and more compact and is called the B-horizon or the middle layer.

  • The third layer is the C-horizon, which is made up of small lumps of rocks with cracks and crevices.

  • Below this layer is the bedrock, which is hard and difficult to dig with a spade.

This diagram shows the layers of soil

Layers of the Soil

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Question 8:

Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 mL of water to percolate through the soil sample. Calculate the rate of percolation.

Answer:

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