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The common physical properties of soil are:
1. Texture,
2. colour,
3. effective depth,
4. structure,
5. permeability,
6. moisture- holding Capacity,
7. surface drainage,
8. slope and erosion.
The three measures to conserve the soils are:
1. Scientific land use i.e. using land for the purpose it is most suited.
2. Crop rotation.
3. Contour ploughing and bunding.
The characteristics are:
i. It is rich in nutrients necessary for basic plant nourishment. This includes nitrogen, phosphorus and potassium.
ii. It consists of adequate minerals such as boron, chlorine, cobalt, copper, iron, manganese, magnesium, molybdenum, sulphur and zinc. These minerals promote plant nutrition.
iii. It contains soil organic matter that improves the structure of the soil. This enables the soil to retain more moisture.
iv. It has a good soil structure which results in well-drained soil.
v. It consists of a variety of micro-organisms that support plant growth.
vi. It often contains large amounts of topsoil.
The distribution:
i. Alluvial soils are widespread in the northern plains and the river valleys.
ii. These soils cover about 40 per cent of the total area of the country.
iii. They are depositional soils, transported and deposited by rivers and streams.
iv. Through a narrow corridor in Rajasthan, they extend into the plains of Gujarat.
v. In the Peninsular region, they are found in deltas of the east coast and in the river valleys.
Sheet erosion takes place on level lands after a heavy shower and the soil removal is not easily noticeable.
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The characteristics are:
1. Alluvial soils are deposited by river.
2. These soils are limited to river basins and plains.
3. These are very fertile soils.
4. These consist of fine-grained clay and sand.
5. These soils are rich in potash but poor in phosphorus.
6. These are generally deep soils.
The characteristics:
1. These are shallow, acidic and less fertile.
2. These are less fertile due to leaching of soil.
3. These are poor in nitrogen, potash but rich in iron.
These are found in Tamil Nadu.
Black soils are derived from Deccan lavas.
Their important characteristics are:
A fairly large area of arable land in the irrigated zones of India is becoming saline because of overirrigation. The salt lodged in the lower profiles of the soil comes up to the surface and destroys its fertility.
Describe the features of forest soils.
The features are:
i. Forest soils are formed in the forest areas where sufficient rainfall is available.
ii. The soils vary in structure and texture depending on the mountain environment where they are formed.
iii. They are loamy and silty on valley sides and coarse-grained in the upper slopes.
iv. In the snow-bound areas of the Himalayas, they experience denudation, and are acidic with low humus content.
v. The soils found in the lower valleys are fertile.
Soil degradation:
i. It defined as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse.
ii. Soil degradation is the main factor leading to the depleting soil resource base in India.
iii. The degree of soil degradation varies from place to place according to the topography, wind velocity and amount of the rainfall.
Factors of pedogenesis are discussed below:
(i) Parent Material: The parent material is derived from the rock exposed to the weathering agents. It determines the type, colour and fertility of the soil. For example, the soil which is formed by lava is black in colour and is fertile.
(ii) Relief: The variation of the slope of land determines the degree of its deepness and fertility. If the slope is steep, the soil cover is thin or shallow and less fertile due to the intensive erosive activity there. On the other hand, if the slope is gentle, the soil cover is deep and rich.
(iii) Climate: The elements of climate such as temperature and rainfall affect the soil formation through their amount and seasonal distribution. Climate controls the type and effectiveness of weathering of parent material, the quantity of water seeping through the soil and the type of micro-organisms present there.
(iv) Natural Vegetation: The natural vegetation provides the much-needed content of humus through its decayed leaf material. The densely forested areas of the country contain some of our best soils.
Soil exhaustion refers to the lost of fertility due to excess use of land and improper methods of cultivation. We can guard our soils against the danger of soil exhaustion by adopting the following techniques:
1. Keeping the land fallow
2. Rotation of crops
3. Combination of crops.
Write short notes on Laterite Soils.
iv. Laterite soils are widely cut as bricks for use in house construction.
v. The laterite soils are commonly found in Karnataka, Kerala, Tamil Nadu, M.P. and hilly areas of Orissa and Assam. Cotton, rice, wheat, pulses, tea and coffee are grown in these soils.
cultivation and are known as ‘cotton soils’. These soils are compared with Chernozem soils of Russia and Prairies soils of U.S.A. These soils can hold water. These soils are also suitable for wheat, jowar, sugarcane, tobacco and oil seeds.
Distinguish between Light and Heavy soils.
Light Soil: Light soil has a large amount of sand.
Heavy Soil: Soils in which large amounts of clay is found are known as heavy soils.
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Khadar |
Bangar |
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1. Found in the lower level in the plains near the rivers. 2. Loamy, and porous soil.
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1. Found at higher level in the plains at river terraces away from rivers. 2. Clayey and non-porous. 3. Less fertile than Khadar due to old deposits. |
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Alluvial Soil |
Black Soil |
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1. It is a transported soil. 2. It is formed when the river deposits its load as it flows from the upper to the lower course. 3. It is the most important soil for agriculture. 4. It is rich in mineral, especially in potash. |
1. Black soil is clayey in nature. 2. It has a great capacity to retain moisture. 3. It develops deep cracks due to dry condition which help in aeration (air circulation). 4. When wet, the soil becomes sticky and is difficult to work with. |
The ways are mentioned below:
i. The first step in any rational solution is to check open cultivable lands on slopes from farming.
ii. Lands with a slope gradient of 15 - 25 per cent should not be used for cultivation.
iii. If at all the land is to be used for agriculture, terraces should carefully be made.
iv. Over-grazing and shifting cultivation in many parts of India have affected the natural cover of land and given rise to extensive erosion. It should be regulated and controlled by educating villagers about the consequences.
Causes of Soil Erosion:
The following factors are responsible for the soil erosion :
1. Excessive grazing by cattle on the slopes of hill causes rapid soil erosion.
2. Potato cultivation in Meghalaya and in the Nilgiri hills cause soil erosion.
3. Clearing of forests in the Himalayas and on the Western Ghats.
4. Jhum cultivation practiced by the tribal people in different parts of the country has caused considerable depletion of the soils.
5. Steep slopes affect the rapidity of running water and the intensity of soil erosion increases.
6. Torrential rainfall i.e. heavy rainfall loosens the soil particles and scoopes out the soil forming gullies and ravines.
7. Strong winds also cause soil erosion. They blow away soils in dry areas.
8. Deforestation - it means the removal of forest cover and it exposes the area to soil erosion.
The following are the measures to conserve the soils :
1. Scientific land use.
2. Scientific crop rotation.
3. Contour ploughing and bunding.
4. Afforestation, especially in the upper reaches of river basins.
5. Construction of barriers against water gullies in wet regions.
6. Increased use of organic manures.
7. Replacing flood irrigation by sprinklers and drip irrigation.
1. Afforestation: In some areas the original vegetation cover has been removed such as the Siwalik Hills. In such areas afforestation and reafforestation is needed to hold the soil.
2. Controlled grazing: The number of cattle grazing the slopes should be according to the carrying capacity of pastures.
3. Terraced agriculture: Slopes must be cut into a series of terraces for cultivation so as to slow down inflow of rainwater.
4. River dams: River dams should be built in the upper course of rivers to control floods and check soil erosion.
5. Contour ploughing: Contour ploughing, terracing and bunding should be done to check soil wash on slopes. Ploughing is done at right angles to the hill slopes.
(i) Parent material; (ii) Relief features, (.iii) Climate, (iv) Natural vegetation.
These factors affect soil formation and create distinction in the soils of the different regions of India in the following ways :
1. Parent material : The parent material is derived from the rock exposed to the weathering agents. It determines the types, colour and structure of the soil. Its fertility also depends upon, the constituents of the rock. For example, the soil which is formed by lava, is black and has rich fertility.
Moreover, if the soil is deposited by running water, it has little relation with surface rock. For example, the soils of plains of India are deposited by the rivers flowing from the Himalayan and plateau regions. They consist of fine grains of loamy, sand and clay. Hence, they have high degree of fertility.
On the other hand, soils of the plateau regions are poor. They are closely related to the parent rocks. They are coarse-grained and less fertile.
2. Relief features : The relief features affect the soil formation in various ways. The variation of slope of land determines the degree of its deepness and fertility. If the slope is steep, the
soil cover is thin or shallow and less fertile due to intensive erosive activity there. On the other hand, if the slope is gentle or low the soil cover is deep and rich in its fertility. Because of this reason, the soils of plains and river basins are rich and deep while the soils of the plateau regions are poor and shallow. Hence, the degree of slope largely determines the fertility of the soils.
3. Climate : The elements of climate such as temperature and rainfall affect the soil formation through their amount and seasonal distribution. Climate determines the type of soil and the effectiveness of weathering of the parent rock material, the quantity of water seeping through the soil and the type of micro-organisms present therein.
4. Natural vegetation : The natural vegetation provides the much needed content of humus through its decayed leaf. Hence, the dense forestlands of our country have rich soils.
Characteristics of Peaty Soils:
Naturally determined fertility: The fertility which is seemed naturally in the soil is called naturally determined fertility. It includes the texture, colour and moisture in the soil. The other element of the soil is the amount of humous which is the important factor for the fertility.
Culturally induced fertility: When the soil is made fertile by adding other chemical contents such as fertilizers and other manures.
The four major types of soil are:
1. Black Soils
2. Red Soils
3. Laterite Soils
4. Alluvial Soils
The causes are:
i. excessively intense cultivation and inadequate soil management
ii. salinization of soil.
1. Afforestation : In some areas the original vegetation cover has been removed such as the Siwalik Hills. In such areas afforestation and reafforestation is needed to hold the soil.
2. Controlled grazing : The number of cattle grazing the slopes should be according to the carrying capacity of pastures.
3. Terraced agriculture : Slopes must be cut into a series of terraces for cultivation so as to slow down inflow of rainwater.
4. River dams : River dams should be built in the upper course of rivers to control floods and check soil erosion.
5. Contour ploughing : Contour ploughing, terracing and bunding should be done to check soil wash on slopes. Ploughing is done at right angles to the hill slopes.
6. Crop rotation : Crop rotation system should be adopted and the land should be allowed fallow for sometime.
7. Other methods : In areas of heavy rain basin type of cultivation should be adopted. Tall trees should be grown as wind and shelter breaks belts in areas of strong winds.
The running water or wind loosens soils which are caused due to various activities of man such as deforestation, over-grazing and the irrational methods of cultivation.
Ways of soil erosion : The soils erosion occurs in two ways. They are : (i) Sheet Erosion, (i) Gully Erosion.
(i) Sheet Erosion: It takes place on the gentle slopes where rain water removes the soil in rather uniform thin layers. This results in removal of fine particles from the soil layer over a large area.
(ii) Gully Erosion: It takes place on the steep slopes where the running water cuts easily into the soil and forms deep channels and converts the land into bad land. The ravines of Chambal valley in India are the result of gully erosion.
Methods of Conservation : As the soil is an important resource, so its conservation is necessary. It may be conserved by adopting the following methods :
1. Afforestation, reforestation and checking of blind deforestation.
2. Checking of overgrazing.
3. Terracing the hill slopes before cultivation.
4. Adopting the contour ploughing.
5. Construction of bund across slopes.
6. Strip cropping in dry areas to conserve the sub-soil moisture.
2. Controlled grazing : The number of cattle grazing the slopes should be according to the carrying capacity of pastures.
3. Terraced agriculture : Slopes must be cut into a series of terraces for cultivation so as to slow down inflow of rainwater.
4. River dams : River dams should be built in the upper course of rivers to control floods and check soil erosion.
5. Contour ploughing : Contour ploughing, terracing and bunding should be done to check soil wash on slopes. Ploughing is done at right angles to the hill slopes.
6. Crop rotation : Crop rotation system should be adopted and the land should be allowed fallow for sometime.
7. Other methods : In areas of heavy rain basin type of cultivation should be adopted. Tall trees should be grown as wind and shelter breaks belts in areas of strong winds.
1. Parent material : The parent material is derived from the rock exposed to the weathering agents. It determines the types, colour and structure of the soil. Its fertility also depends upon, the constituents of the rock. For example, the soil which is formed by lava, is black and has rich fertility.
Moreover, if the soil is deposited by running water, it has little relation with surface rock. For example, the soils of plains of India are deposited by the rivers flowing from the Himalayan and plateau regions. They consist of fine grains of loamy, sand and clay. Hence, they have high degree of fertility.
On the other hand, soils of the plateau regions are poor. They are closely related to the parent rocks. They are coarse-grained and less fertile.
2. Relief features : The relief features affect the soil formation in various ways. The variation of slope of land determines the degree of its deepness and fertility. If the slope is steep, the
soil cover is thin or shallow and less fertile due to intensive erosive activity there. On the other hand, if the slope is gentle or low the soil cover is deep and rich in its fertility. Because of this reason, the soils of plains and river basins are rich and deep while the soils of the plateau regions are poor and shallow. Hence, the degree of slope largely determines the fertility of the soils.
3. Climate : The elements of climate such as temperature and rainfall affect the soil formation through their amount and seasonal distribution. Climate determines the type of soil and the effectiveness of weathering of the parent rock material, the quantity of water seeping through the soil and the type of micro-organisms present therein.
4. Natural vegetation : The natural vegetation provides the much needed content of humus through its decayed leaf. Hence, the dense forestlands of our country have rich soils.
2. These soils are limited to river basins and plains.
3. These are very fertile soils.
4. These consist of fine grained clay and sand.
5. These soils are rich in potash but poor in phosphorus.
6. These are generally deep soils.
1. Black Soils: Black soils are mainly found over the Deccan lava tract (Deccan Trap) including Maharashtra, Madhya Pradesh, Gujarat and Andhra Pradesh. These soils are found in river valleys of Narmada, Tapi, Godavari and Krishna. These soils have been formed due to weathering of lava rocks. These soils cover an area of about 5 lakh sq. km. These soils are rich in lime, iron, magnesia and alumina. But these lack in phosphorus, nitrogen and organic matter. These are also called ‘Regur Soils’. These soils are most suitable for cotton cultivation and are known as ‘Black Cotton Soils’ These soils are compared with Chernozem soils of Russia and Prairies soils of U.S.A. These soils can hold water. These soils are suitable for wheat, jowar, sugarcane, tobacco and oil seeds.
2. Red Soils : These soils are found in Chhotanagpur plateau, Telangana, Nilgiris, Tamil Nadu, Karnataka, Andhra Pradesh and
areas of periphery of Deccan plateau. These soils have been formed due to decomposition of underlying igneous rocks under heavy rainfall. These soils have different shades of red and yellow. The red colour of these soils is due to oxidation and diffusion of iron in hard crystalline rocks. These are suitable for the cultivation of millets, pulses, lin–seed, tobacco etc. These soils cover the largest area in Peninsular India, particularly south-east part of the peninsula. These soils are poor in lime, nitrogen and humus. Fertilizers are added to make these fertile.
3. Laterite Soils : Laterite soils are found on the highland areas of the plateau. These are found in Karnataka, Kerala, Tamil Nadu and hilly regions of Assam, Rajmahal hills and Chhotanagpur plateau. Due to monsoonal climate (we,t and dry seasons alternately occurring), there is the leaching of soils due to heavy rains. It washes away the silica content in soils. These are shallow, acidic and less fertile soils. The lowland laterite soils are useful for cultivation of food- grains and other crops. The upland laterite are thin, coarse and infertile. These soils are poor in nitrogen and lime, but rich in iron. So these are suitable for plantation of crops like tea, rubber, coffee etc.
4. Alluvial Soils : These soils are the most widespread soils covering an area of 8 lakh sq. km from Punjab to Assam (the entire northern plains). These cover 22.16 per cent total area. These soils have been deposited by sediments brought by rivers. These are found in river basins, flood plains and coastal areas. These are deep soils rich in potash, but poor in nitrogen. These soils contain fine particles of soils called alluvium deposited over thousands of years. This alluvium has been deposited by three great Himalayan rivers-Sutlej, Ganga and Brahmaputra. These soils are common in the eastern coastal plains.
These soils have been deposited by the rivers in river valleys of Mahanadi, Godavari, Krishna and their deltas. These are deep and fertile soils. These soils are suitable for cultivation of jute, sugarcane etc.
These are of three types :
(i) Khadar soils : The finer and new alluvium deposited in flood plains is called Khadar.
(ii) Bangar Soils: The older alluvium is known as Bangar.
(iii) Newest Alluvial Soils : The fine alluvium in deltas is known as newest alluvial soils.
5. Other Soils :
(a) Desert Soils : These soils cover 2 lakh sq. km area in dry areas of Rajasthan, Gujarat, Punjab, Haryana. These coarse soils are suitable for cultivation of jowar, bajara, cotton etc.
(b) Saline and Alkaline Soils :
These soils are found in dry and marshy areas. These are locally known as Bhur, Rehu, Kallar. The accumulation of salts makes these infertile.
(c) Mountain Soils : These soils are mostly thin and infertile. These include peat, meadow, and forest hill soils.
(i) Stony soils which are coarse and infertile.
(ii) Tea soils found in Dun valleys are suitable for tea cultivation.
(iii) Volcanic soils are found on mountain slopes.
