Notes on Properties of Soils, Class 7,Ch 9

1. Percolation of water through the Soil
Percolation can be defined as the property of the soil by which it allows the flow of water through it. The rate at which water percolates or moves through soils may vary in different kind of soils. Some soils absorb water while others allow it to flow through them. The rate of percolation can be calculated by:
Figure : Percolation of Water
2. Moisture
Moisture is the amount of water that is present in the soil. Even a dry soil has some amount of moisture in the air. However, the clayey soil has the highest content of moisture.
Why air above farmland appears shimmering during the daytime?
We know that soil contains water. Due to sunlight, the water from the soil begins to evaporate and turns into water vapour. This water vapour when reflects the sunlight appears as if it is shining and hence the air above the soil makes the land look shimmery.
3. Absorption
Every soil has a water absorption capacity which depends upon how porous the soil is. Clayey and loamy soils are most porous hence can retain water in large quantities. That is why crops can grow over these soils. Sandy soils, on the other hand, do not absorb water and hence do not support much vegetation.
4. Texture
The texture is the size of particles of the soil. Different kinds of soils have a different texture.
5. Colour
Different soils have different colours as well. This is because of the minerals and nutrients present in the soil. For instance, some soils are black in colour because of the presence of humus and minerals while some soils are red in colour because they have iron in large quantities in them.
Figure : Soils have different Colors
6. Air Content
Since soil is made up of particles of different sizes these particles can be loosely bound or tightly bound. The air often occupies the space in between these particles. This allows life to sustain in the soil such as microorganisms.

Soil and Crops
Different kinds of soils are found in different regions because of the following factors that decide the soil structure of that place:
temperature
humidity
rainfall
sunlight
winds
The type of crops that will grow in the soil depends upon these factors as well as the properties of a soil.
Type of Soil 
Crops Grown 
Sandy 
Potato, Lettuce, Corn, Peppers 
Clayey
Sprouts, Broccoli, Kale, Beans, Cabbage 
Loamy 
Apples, Carrots, Tomatoes, Cucumber

Soil erosion
When the top layer of soil gets removed it is called soil erosion.
The soil erosion mainly occurs when the soil is left loose without vegetation or when deforestation occurs.
In such a situation, strong winds and flowing water or rainwater takes away the topsoil and therefore decrease its quality.
Also, this kills the organisms living inside the soil.
The roots of the plants and trees keep the soil together and allow several microorganisms to grow and survive there. Therefore, it is always advised to plant more trees and avoid deforestation.