1. What is soil?

     Soil is the most important layer of the earth's crust. It is a valuable resource. It is the mixture of rock debris and organic materials which develop on the earth's surface. It forms slowly and is destroyed easily,hence must be conserved if it is to continue to support life.

2. What are the major factors affecting the formation of soil?

     The major factors affecting the formation of soil are relief, parent material climate ,vegetation and other life - forms and time.

3. What is ' Horizon A ' ?

     Horizon 'A' is the topmost  zone,where organic materials have got incorporated with the mineral matter,nutrients and water, which are necessary for the growth of plants.

4. What is ' Horizon B '?

     'Horizon B ' is a transition zone between the ' horizon A ' and ' horizon C ' and contains matter derived from below as well as from above. It has some organic matter in it, although the mineral matter is noticeably weathered.

5. What is ' Horizon C '?

    'Horizon C ' is composed of the loose parent material. This layer is the first stage in the soil formation process and eventually forms the above two layers.

6. What are the classification of soils on the basis of genesis, colour, composition and location?

      On the basis of genesis, colour,composition and location,the soils of India have been classified into :

          (i)    Alluvial soils
          (ii)   Black soils
          (iii)  Red and Yellow soils
          (iv)  Laterite soils
          (v)   Arid soils
          (vi)  Saline soils
          (vii)  Peaty soils
          (viii) Forest soils

7. What are alluvial soils?

     Alluvial soils are widespread in the northern plains and the river valleys. These soils cover about 40 per cent of the total area of the country. They are deposited soils,transported and deposited by rivers and streams. Though a narrow corridor in Rajasthan,they extend into the plains of Gujarat.In the peninsular region,they are found in deltas of the east coast and in the river valleys.The alluvial soils vary in nature from sandy loan to clay.

8. What is black soil?

     Black soil is formed by the breaking down of the volcanic rocks. This soil is black in colour and porous. It holds much moisture.Such soil is suitable for growing cotton. These soils are also known as the ' Regular soil ' or the ' black cotton soil '. The black soils are generally clayey, deep and impermeable. They swell and become sticky when wet and shrink when dried so,during the dry seasons,these soil develop wide cracks.

9. What is red soil?

     Red soil develops on crystalline igneous rocks in areas of low rainfall in the eastern and southern part of the Deccan plateau. This soil is good for the cultivation of soil seeds and millets.

10. What is laterite soil?

      The soil which is very poor in mineral content is called laterite soil. This soil is develop in areas with high temperature and high rainfall. These are the result of intense leaching due to tropical rains. With rain , lime and silica are leached away , and soils rich in iron oxide and aluminium compound are left behind. Humus content of the soil is removed fast by bacteria that thrives well in high temperature. These soils are poor in organic matter, nitrogen , phosphate and calcium , while iron oxide and potash are in excess.

11. What is arid soils?

       Arid soil range from red to brown in colour. They are generally sandy in structure and saline in nature. In some areas, the salt content is so high that common salt is obtained by evaporating the saline water. Due to the dry climate,high temperature and accelerated evaporation,they lack moisture and humus.Arid soils are characteristically developed in western Rajasthan, which exhibit characteristic arid topography. These soils are poor and contain little humus and organic matter.

12. What are saline soils?

       Saline soils contains a larger proportion of sodium, potassium and magnesium, and thus, they are infertile, and do not support any vegetative growth. They have more salts, largely because of dry climate and poor drainage.They occur in arid and semi-arid regions,and in waterlogged and swampy regions. Their structure ranges from sandy to loamy . They lack in nitrogen and calcium.

13. What are peaty soils?

       Peaty soils are found in the areas of heavy rainfall and high humidity,where there is a good growth of vegetation.Thus, large quantity of dead organic matter accumulates in these areas, and this gives a rich humus and organic content to the soil. Organic matter in these soils may go even up to 40 - 50 per cent .These soils are normally heavy and black in colour.

14. What are forest soils?

       Forest soils are formed in the forest areas where sufficient rainfall is available. The soils vary in structure and texture depending on the mountain environment where they are formed. They are loamy and silty on valley sides and coarse-grained in the upper slopes. In the snow bound areas of the Himalayas , they experience denudation , and are acidic with low humus content. The soils found in the lower valleys are fertile.

15. Define soil degradation?

      Soil degradation can be defined as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse.