Soil is defined as upper layer of the earth composed of loose surface material. It is the mixture of rock debris and organic materials which develop on the earth’s surface.
Soil Profile
Soil is made up of different layers like - O, A, E, B, C, R
- O- The O horizon, which is the organic layer of soil commonly referred to as humus, can vary in thickness depending on the type of soil. In some soils, the O horizon may be thin, while in others it can be thick or even absent.
- A - It is called as topsoil and Mostly minerals from parent material with organic matter incorporated.
- E -refers to eluviated soil, which has undergone a process of leaching that removes clay, minerals, and organic matter. This results in a higher concentration of sand and silt particles in the soil.
- B- means subsoil and it is Rich in minerals that leached (moved down) from the A or E horizons and accumulated here.
- C- means parent material and The deposit at Earth’s surface from which the soil developed.
- R- means bedrock) and it is mass of rock such as granite, basalt, quartzite, limestone or sandstone that forms the parent material for some
The classification of Indian soil
The classification of Indian soil by ICAR is widely accepted and they have divided Indian soil into 8 groups
Indian soil is classified as follows
1. Alluvial Soils
- Alluvial soils are present in approximately 40% of the country's total area.
- These soils are formed through transportation and deposition by rivers and streams.
- Alluvial soils are classified as depositional soils.
- These soils constitute the surface of the Great Plains from Punjab to Assam.
Region-
- These soils constitute the surface of the Great Plains from Punjab to Assam. They also occur in the valleys of the Narmada and Tapi in Madhya Pradesh and Gujarat, Mahanadi in Chhatisgarh and Odisha, Godavari and Krishna in Andhra Pradesh, and Kaveri in Tamilnadu.
- In the Peninsular region, they are found in deltas of the east coast and in the river valleys.
Composition-
- Alluvial soils are generally deficient in nitrogen, phosphorus, and humus
- They are generally rich in potash but poor in phosphorous
Color-
- The colour of the alluvial soils varies from the light grey to ash grey
- The alluvial soils of Odisha and Chhatisgarh are light sandy and of yellow colour. Andhra coastal region has black alluvial soils along its long coastal line and Godavari- Krishna delta
Further division-based upon geological characteristics-
Bhangar –
- It represents a system of older alluvium .
- They have more clayey composition and darker colour.
- These are coarser in texture and contain nodules (Kankar) and are found higher up in the plains at river terraces away from rivers
Khadar-
- It represents a system of newer alluvium.
- These are flooded almost every year and occur near river bed where deposition takes regularly
Bhabar and Terai Soils-
- Shiwalik foot hills is composed of alluvial fans with coarse, often pebble soils.
- The zone is called Bhabar. It is a long narrow strip of swampy land with salty soils. To its south occurs the swampy lowland with salty soils and known as Terai
2.Black Soil-
- These soils occupy over 5.46 lakh sq. km. area which is around 16.6 percent of the total geographical area
- These soils are also known as the ‘Regur Soil’ or the ‘Black Cotton Soil’
Distribution
- It covers most of the Deccan Plateau especially the region in Maharastra and Madhya Pradesh is known as Deccan Trap.
- It is also found in most of Gujarat northern parts of Karnataka, South Chhatisgarh, South Odisha, West and south parts of Andhra Pradesh, Western Tamilnadu, Bundi and Tonk districts of Rajasthan and plateau region of Uttar Pradesh
Features-
- These types of soils exhibit the property of swelling and becoming sticky when wet, while shrinking upon drying. As a result, extensive cracking occurs during the dry season, leading to a process known as "self-ploughing."
- This property helps in moisture retention of the soil
- These are very fertile and are being used without adding fertilizers and manures. These are clayey in nature with fine grained particles. These are highly retentive of moisture
- The black colour is due to its iron content
Composition-
- The black soils are rich in lime, iron, magnesia and alumina.
- They also contain potash But they lack in phosphorous, nitrogen and organic matter
Crops-
- cotton and other than cotton, this soil is favorable for the cultivation of crops like sugarcane, wheat, onion and fruits
3.Red and Yellow Soil
- Red and yellow soils originate from metamorphic and crystalline rocks, with parent rocks consisting of acid granites, gneisses, quartzitic and felspathic materials.
- Iron compounds present in the soil give it a reddish hue.
- When hydrated, the soil appears yellow in color.
- It is thicker in the plain areas and are more fertile than on the slopes of the hills
Distribution-
- Most part of south India has the distribution of these soils. They occupy the states of Kerala, Tamilnadu, Karnataka, Goa, eastern parts of Andhra Pradesh, Odisha, eastern Madhya Pradesh, plateau districts of Uttar Pradesh
Composition-
- generally poor in nitrogen, phosphorous and humus.
Crops-
- Rice, wheat, sugarcane, tobacco, cotton and pulses are grown on it with the use of fertilizers. Groundnut and potato are also grown on upland soils.
4.Laterite Soils
- Laterite soils are named after the Latin word "later," which means brick.
- These soils are formed in areas with high temperature and rainfall, where wet and dry periods alternate.
- Intense leaching caused by tropical rains is responsible for their formation.
- Bacteria that thrive in high temperatures rapidly remove humus content from the soil.
Crops-
- It is not suitable for cultivation but it does support pastures and scrub forests. With the use of manures sugarcane, Ragi and rice are cultivated on low lands, coffee, rubber, cashew and tapioca crops are also cultivated.
Distribution-
- The laterite soils are commonly found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh and the hilly areas of Odisha and Assam.
Composition-
- The process of rain leaches lime and silica from the soil.
- As a result, the remaining soil becomes rich in iron oxide and aluminum compound.
- However, these soils are deficient in organic matter, nitrogen, phosphate, and calcium.
- On the other hand, there is an excess of iron oxide and potash in these soils.
5.Desert Soils
- These soils are formed under arid and semiarid conditions in the north-western parts
- Arid soils range from red to brown in colour. They are generally sandy in structure and saline in nature.
Distribution-
- The entire area west of the Aravalli Range in Rajasthan, Rann of Kutch, southern districts of Haryana and Punjab
Composition-
- They lack moisture and humus. Nitrogen is insufficient and the phosphate content is normal.
Crops-
- With irrigation facility, this soil grows crops like wheat, gram , jowar, bajra, grapes and melon
6.Saline Soils
- These soils are li able to saline and alkaline efflorescence's and are known by different names such as reh, Kallar, usar and chopan
- These are formed due to ill drainage which causes water logging.
- Dissolved salts sodium, calcium and magnesium in the sub soil are carried to the surface by capillary action, when water is evaporated.
- Reh- Reh is a mixture of sodium carbonate, sulphate, chloride, calcium and magnesium salts
Distribution-
- Western Gujarat, deltas of the eastern coast and in Sunderban areas of West Bengal
- In the Rann of Kuchchh, the Southwest Monsoon brings salt particles and deposits there as a crust. Seawater intrusions in the deltas promote the occurrence of saline soils
7.Peaty Soils-
- They are found in the areas of heavy rainfall and high humidity, where there is a good growth of vegetation
- They have high humus content
Distribution-
- It occurs extensively in the northern region of Bihar, the southern region of Uttarakhand, as well as in the coastal regions of West Bengal, Kerala, Odisha, and Tamil Nadu.
Composition-
- These are highly acidic, heavy and black
8.Marshy Soils-
- The soil is useful for the cultivation of Jute.
- These are found in the coastal areas of Odisha, Tamandu, Sundarbans of west Bengal, mid parts of Bihar and Terai belts of Uttar Pradesh.
- It contains a high proportion of iron and organic substances
9.Mountain Soils-
- Various soil characteristics can be observed in mountainous regions, ranging from deep alluvial soils in river basins and lower slopes to residual soils with a high gravel content at higher elevations.
- Large homogenous soil groups are not found in mountainous areas due to complex topographic, geologic, vegetation and climatic conditions.
- The Himalayan snow-bound areas go through denudation and exhibit low humus content and acidic properties.
- Lower valleys in mountainous regions are home to fertile soils.
Distribution-
- These are found in the hilly regions of Jammu & Kashmir, Himachal Pradesh, Uttrakhand, Sikkim and eastern states
Characteristics of Indian soil
Soil Erosion
- Soil erosion is defined as removal of upper portion of the soil due to natural; and manmade reasons.
- There are many physical and social factors which determine the extent and severity of soil erosion.
- Soil erosion by ravines and gullies is widespread in India, It has been estimated that 3.67 million hectares of soil surface is damaged.
There are four major areas of ravines and gullies in India.
They are-
(1) Yumuna-Chambal ravine zone,
(2) Gujarat ravine zone,
(3) The Punjab Siwalik foothills zone and
(4) Chhotanagpur zone.
Erosions due to rivers
- Rivers cause erosion in various regions, including the Mahanadi valley, upper Son valley, upper Narmada and Tapi valleys, Siwalik and Bhabar tract of the western Himalayan foothills, and edges of Ganga Khadar in western Uttar Pradesh.
- On the other hand, there are areas that are relatively less affected, such as the entire Deccan region south of the Godavari, the Ganga-Brahmaputra plains east of Varanasi, Kutchchh, and western Rajasthan.
- Sheet erosion is prevalent in sloping deforested terrain, unterraced uplands of the Peninsular region, Sutlej-Ganga plains, Coastal plains, Western Ghats, and Northeastern hills.
- The regions mentioned above experience widespread sheet erosion.
Erosion in Desertic area
- In the last 50 years, the Rajasthan desert has encroached upon 13000 hectares of land in Rajasthan, Gujarat, Haryana and Uttar Pradesh. The sand dunes and deforestation of surrounding areas of desert and wrong practices of agriculture combine with climate change is also the major cause of Erosion in Desertic area of India
Glacial erosion and coastal erosion-
- Glacial erosion is limited to high Himalayas and hilly areas like Himachal Pradesh, Uttarakhand And north-eastern Himalayan states and sea erosion is confined to coastal areas only.