Soil

Soil is the uppermost layer of the earth’s crust. It contains a mixture of fine powdered rock material and humus. Humus is the organic matter which is added to the soil by the decayed and decomposed remains of plants and animals. The presence of humus in soil makes it fertile. Soil is formed as a result of weathering, erosion and deposition of rock material. The process of soil formation is very slow. It may take thousands of years to complete 2-3 cm thick layer of soil.

Soil Classification
Soils can be classified in many different ways. Some important soils are described as under :

1. Podzol Soil : These are ashgrey  coloured soils. These are found in high-latitude coniferous forest belt having very long cold winters, short cool summers and a  moderate precipitation throughout the year. These soils are acidic, infertile and of limited value for agriculture. These are useful for dairying and mixed farming.

2. Laterite Soil: This soil is found in the hot and humid areas mainly in the equatorial regions. This soil is heavily leached due to  high rainfall, and is not useful for agriculture. This soil is red-brown in colour.

3. Tundra Soil : This type of soil develops in very cold climates. This soil is found covered with thick layers of lichens and mosses.

4.Chernozem Soil: This soil is also known as black soil. It is one of the most fertile soils of the earth. It is found in the steppes of Ukraine, the central part of the USA, Central Africa, South America and Australia.

5. Prairie Soil : This soil is similar to chernozem but it lacks the excess of calcium carbonate. Maize is the main agricultural product of this soil.

6. Chestnut Soil : Its belt, lies towards the drier parts of chernozem in Asia and North America.

7. Desert Soil: This is found in the desert areas of temperate and tropical zones having low rainfall. It is grey in colour in temperate regions and red in the hot deserts. It is characterized by low rainfall, high temperature and high evaporation. It is  unleached and alkaline and lacks humus or organic matter.

8. Bog Soil : This soil is found in marshy areas of humid climate. It remains saturated with water.

9. Meadow Soil: This soil is found in the flood-prone areas where water drainage is better than that in the marshes. This soil remains covered with a thin layer of humus which supports the growth of grasses.

10. Saline Soil : This soil is mainly confined to the steppes and arid regions and is not good for agriculture.