2. Name what type of soil is it, According to their size?
(a) Greater than 2 mm in diameter (b) 0.005–0.05 mm in diameter
3. What is the last stage in the formation of soil?
4. What are the factors which influenced the formation of soil?
5. What is the composition of soil?
6. Which type of soil is classified as residual soil? Give example.
7. The soil at a given place was found to consist of sandstones, clay, shale and limestone. What type of soil is it and how it might have formed?
8. Mention all possible composition of soil.
9. Name physical and chemical properties of Soil.
10. Write a short note on A–horizon and B–horizon.
11. Write a short note on transported soils.
12. What are the main causes for the erosion of soil?
13. How will you demonstrate that the vegetation prevents erosion of SOIL
1. Soil forms the outer most layer of land on the earth. Its thickness on the earth’s surface ranges from a few millimeters to 3 – 4 meters.
2. Soil with particle size greater than 2 mm in diameter is gravel; that with particle size varying from 0.005 mm to 0.05 mm is known as silt.
3. The addition of organic matter from dead and decomposed plants and animals is the last stage in the formation of soil.
4. The formation of soil is influenced by climate, vegetation, parent materials and time factors to a great extent.
5. Generally soil contains fine particles of rock, humus, air and water. 6. The soil which remains at the place of its formation is called residual soil. The residual soil may be red or black or even laterite.
7. The soil containing sandstone, clay, shale’s and limestone is known as mountainous soil.
This type of soil is found in depression and valley basins or an gently inclined slopes. It is probably formed by weathering.
8. The soil is made up of mineral particles, organic matter, solutions of various inorganic salts in water, air and living organism.
9. The physical properties of soil include its texture, structure, colour, porosity, water holding capacity and presence of soil organism.
The chemical properties, like acidity and alkalinity of the soil, have a relation with the type of vegetation and crops grown on it. Temperature may affect biological, physical and chemical composition of soil.
10. The soil is arranged in two or more layers or horizons. The upper most layer is generally dark in colour, as it is rich in minerals and humus. This layer is soft, porous and can retain more water. It is called the top soil or the A–horizon.
The next layer has lesser amount of humus or organic matter, iron oxide and more minerals.
This layer is generally harder and more compact and is called the B–horizon or the middle layer.
11. The soil which settles at other places as a result of its transportation by gravity, flowing water, wind and glacier is called transported soil. Transported soil is further classified into various types depending upon their mode of transportation. Various types of transportation soil are alluvial type and sandy soil.
12. Erosion of soil is natural process. It is as old as the earth itself. Erosion involves the movement of soil from one place to another. It may be due to the flowing water or wind.
Now a day, the rate of soil erosion is very high due to increase in the activities of humans.
The rate of soil erosion is higher in region with high population density, mainly due to increase in the agricultural activities.
Continuous cultivation of land by only one type of crop further adds to the loss of soil fertility.
Deforestation, floods and overgrazing are some other main causes for the erosion of soil.
The forest fires and even deep ploughing of land for crops also lead to soil erosion.
13. Water and wind, take away the top layer of the soil, where there is no vegetation or poor vegetation. The tree, grasses and hedges hold the soil in place.
This can be mode clear by the following activity.
Take two trays or baskets.
Fill them with garden soil. Grow grass or some cereal in one of them and water it properly for a few days.
Now keep both the trays in a slightly inclined position by placing a brick below their one side.
Let allow the water to fall on both the trays.
we will find that the water that flows from the tray with vegetation contains fewer amounts of soil particles in it.
This is due to the fact that the roots of plants bind the soil and do not allow it to flow with water.