Soil is the mixture that develops on the surface of the earth and soil is the mixture of organic materials and rock debris.
Factors affecting soil formation
Relief
Parent material
Climate
Vegetation
Other life-forms and time
Human activities (also influences soil formation)
Components of the soil
Mineral particles
Humus
Water
Air
Layers of the soil
Soil consists of three layers, called Horizons.
Horizon A (Topmost zone)
Horizon B is the transition zone between the Topmost zone i.e. 'horizon A' and First stage of soil formation i.e. 'horizon C'.
Horizon C is composed of loose parent material and it is the first stage in the soil formation process and forms the two above layers.
Classification of Soils
India has various types of soils.
Classification in ancient times-
Two groups were used to classify the soil in ancient times - Urvara and Usara.
Urvara means fertile
Usara means sterile
In the 16th century A.D.,
Inherent characteristics and external features were used to classify soils in the 16th century A.D.
Soil texture, colour, slope of land and moisture content in the soil.
Indian Council of Agricultural Research (ICAR) has classified the Indian soils on the basis of their nature and character as per the United States Department of Agriculture (USDA) Soil Taxonomy, into the following order:
The Indian Soil are classified into following on the basis of genesis, colour, composition and location.
1. Alluvial soils
2. Black soils
3. Red and Yellow soils
4 Laterite soils
5. Arid Soils
6. Saline soils
7. Peaty soils
8. Forest soils
1. Alluvial soils
40% of the total area of India is covered by Alluvial soils
widespread in the northern plains and the river valleys.
Transported and deposited by rivers and streams. Hence, they are depositional soils.
Nature - Sandy loam to clay.
Rich in potash
Poor in phosphorous.
2. Black soils/Regular Soil/Black Cotton Soil
Most of the Deccan Plateau is covered by Black Soil
This soil is very deep.
Nature - generally clayey, deep and impermeable
color- deep black to grey.
This soil develop wide cracks in the dry season.
Rich in lime, iron, magnesia and alumina
Poor in phosphorous, nitrogen and organic matter
It develops in low rainfall areas in the eastern and southern part of the Deccan Plateau. on crystalline igneous rocks.
3. Red and Yellow soils
It develops a reddish colour.
Looks yellow in a hydrated form
Poor in nitrogen, phosphorous and humus.
4 Laterite soils
It develops in areas with high temperature and high rainfall.
Rich in iron oxide and potash
Poor in organic matter, nitrogen, phosphate and calcium,
Manures and fertilisers are essential to make the soil fertile.
5. Arid Soils
Nature - saline
Structure - generally sandy
Due to high temperature, accelerated evaporation and dry climate. this type of soil lacks moisture and humus.
Poor in Nitrogen
6. Saline soils
Rich in sodium, potassium and magnesium.
Infertile because of the above mentioned point.
Do not support vegetative growth.
Lack in nitrogen and calcium.
7. Peaty soils
40-50% of Organic matter are found.
Found in the areas of high humidity and heavy rainfall
Colour- normally in black
8. Forest soils
It requires sufficient rainfall.
Structure and texture depends on the mountain environment
The soils found in the lower valleys are fertile.
