Formation of Soil – Soil Formation

Back to: Agricultural Science Primary 4

 

Welcome to class! 

In today’s class, we will be talking about the formation of soil. Enjoy the class!

Formation of soil

Soil is formed in four main ways

1. Through the breakdown of rocks into small particles by man, animals, and plant roots.
2. By the washing down of rock particles by water and wind.
3. Through heating of rocks by sunshine.
4. By the decay of plants and animals to form soil organic matter.

Soil formation through breaking of rock

A rock is a big stone seen above the soil. Some farmers dry their crops on flat rocks. Some people build houses on rocks. Others sit on a rock to rest, while some walk across it. All these activities of man help to break down rocks into small pieces.

Plants also help to break rocks into small particles as their roots crack rocks, especially trees, which have very large roots. The breaking down of rocks into small pieces by man’s activities and plants helps to form soil.

1. Washing down of rock particles:

The two major agents that cause this are water and wind. . When wind blows on a rock and rain falls on it, they can break it down into particles that form soil.

2. Heating of rocks by sunshine:

The image below shows rays of sun falling on a rocky hill. These hot rays heat up the rock, and it cracks in the process. The cracks form small particles. What happens to these particles? Heat from the sun helps to break rocks into small particles to form soil.

3. The decay of plants and animals

Dead plants and animals decay to form soil. Daily in the environment, plants and animals die as a result of one thing or the other. They decay and over time mixes and form soil.

Decayed plants and animals form organic matter which helps to form soil.

General evaluation

1. What is soil?
2. State four ways that soil is formed

Weekend assignment

1. When plants and animals die, they decay and form ———- a) Soil b) dead bodies c) rock
2. Soil can be formed when rays of sun heats a ———- a)  Plant      b) water body      c) Rock
3. The two major agents that washes away rock particles are ——— and ———- a) Wind and water b) wind and sand     c) sand and water

Theory

1. Explain two methods by which soil is formed.

 

In our next class, we will be talking about Properties of Soil: Physical Properties.  We hope you enjoyed the class.

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