To provide you with an insight into the topic "Soil", complete study notes on the Soil for NABARD Grade-A Exam 2021 is provided below. You can also download the PDF of NABARD Grade A notes from the link provided at the end of the study notes.
What is soil?
The loose material or upper layer of the mantle rock (regolith- a layer of loose heterogeneous material covering solid rock) consisting mainly of very small particles and humus which can support the growth of plants is known as soil.
Composition of soil
In general, the soil is made up of four elements:
- Inorganic or mineral fraction (derived from parent material)
- Organic matter (decayed and decomposed plants and animals)
Naturally occurring soil is made up of
a. Parent material
c. Physical, chemical and biological agents (micro-organisms)
d. Land use practices
Characteristics of Soil
- It includes hard resistant rocks such as granite, marble as well as slate
- less resistant rocks such as recent volcanic lavas and ashes, the metamorphic rocks like schist, gneiss) and the sedimentary rocks (sandstone, clay, silt and limestone).
- The term rock will also include clay, gravel, unconsolidated sands, alluvium (less soil-resistant).
- The structureless dark-brown end product of dead organic material found within the soil surface is known as humus.
- Humus helps in the maintenance of soil fertility and the amount of humus varies in different soil.
- Soil is characterized by the size of its particles.
- Clayey soil is fine, sandy as coarse, while silt is an intermediate.
- The standard unit for the measurement of soil particles in the millimeter, but the smaller unit is micron.
|Sandy Soil||Between 0.05 and 0.02mm|
|Silty Soil||Between 0.02 and 0.002mm|
|Clay Soil||0.002 mm in diameter|
It is the arrangement of soil particles. The way in which sand silt clay and humus bond together to form beds is knowns as soil structure.
- The acidity and alkalinity of soil are expressed in the pH value.
- PH is a scale that measures the concentration of hydrogen ions held by the soil colloids (particles).
- Neutral soil has a pH value of about 7.2 and acid soil less than 7.2.
- Strongly alkaline soil has a pH value of about 8 or higher.
- The air content of the soil is vital as it helps in the process of oxidation which converts nitrogen into a form readily available to plants.
- A higher degree of oxidation consumes organic material and makes soil sterile.
- Infinite bacteria present in soil need oxygen for breaking down plants and animals and are called aerobic.
- Depending on the texture of soil water moves downward by percolation.
- The movement of water into the soil is called infiltration, and the downward movement of water within the soil is called percolation, permeability, or hydraulic conductivity.
- Pore space in soil is the conduit that allows water to infiltrate and percolate. It also serves as the storage compartment for water.
- Permeability also varies with soil texture and structure. Permeability is generally rated from very rapid to very slow.
- It is a layer of soil which lies more or less parallel to the surface and has fairly distinctive soil properties.
- It is a distinct layer within the soil that differs chemically and/or physically from the layer below or above.
It is a vertical series of soil horizons from the ground surface to the parent rock.
Classification of Soil in India
The first scientific classification of Indian soil was made by Voelker and Leather. They classified soil into 4 categories:
|Voelker and Leather Classification|
1. Alluvial soils
2. Regur (black-earth) soils
3. Red soil
4. Lateritic soil
• Recently the Indian Council of Agricultural Research, on the basis of texture, structure, color, pH value, and porosity has identified the following types of soil groups.
It covers about 143.1 million sq km for about 43.4 percent of the total reporting area.
- It occurs mainly in the Satluj Ganga Brahmaputra Plains also in the valleys of Narmada, Tapi, and in the Eastern and Western coastal plains.
- They are mainly derived from the debris brought down from the Himalayas or from silt left out by the retreating sea.
- It is rich in humus, phosphoric acid, lime, and organic matter but deficient in potash.
- The color of the soil varies from light grey to ash grey and the texture is sandy to silty-loam.
- These soils are further divided into two:
- Khadar Soil
- Bhangar Soil
Khadar Soil: The khadar tracts are rich in concretions, and nodules of impure calcium carbonate or kankar. They are low lying, frequently inundated by floods during the rainy season. In the drier areas, it also exhibits stretches of saline and alkaline efflorescence locally known as reh, kallar or Thur.
Bhangar Soil: It is above flood level and is generally well-drained but contains concretion (kantars) of impure calcium carbonate. The texture of soil varies from loamy soil to clayey soil. It is suited to wheat, rice, maize, sugarcane, pulses, oilseeds, berseem, fruits, and vegetables.
- It covers the second largest area of about 61 million hectares or 18.5 percent of the total reporting area.
- It is red in color because of ferric oxides. The top layer is red while the horizon below is yellowish in color.
- The texture of soil varies from sandy to clay and loam.
- Developed on Archaean granite, these soils are also known as the omnibus group.
- They are mainly found over the Peninsula from Tamil Nadu in the south to Bundelkhand in the north, and raajmahal in the east to Kathiawar and Kachchh in the west.
- These soils are also found in tracts in western Tamil Nadu, Karnataka, southern Maharashtra, Andhra Pradesh Chhattisgarh, Jharkhand, Orissa, and scattered patches in Rajasthan.
- They are porous and friable and have an absence of lime, kankar, and carbonates and a small number of soluble salts.
- Intense leaching is a menace to these soils.
- These soils are poor at uplands as it is thin, gravelly, sandy or stony and porous but better in lower plains and valleys as it rich, deep, dark-colored fertile loams.
- They are devoted to wheat, cotton, pulses, tobacco, millets, oilseeds potato, and orchards.
Black soil/Regur (cotton-soil) Soils
- Internationally known as tropical chernozems are the third-largest soil group in India.
- They are spread about 50 million hectares accounting for 15 percent of the total reporting area of the country.
- They are considered to be mature soils and the color of these soils varies from deep black to light black.
- They get their parent material from the weathered rocks of Cretaceous lava and have high water-retaining capacity.
- They are highly productive and well suited for the production of cotton, pulses, millets, castor, tobacco, sugarcane, vegetable, and citrus fruits.
- The texture of the soil is clayey and is rich in iron, lime, calcium, potash, aluminum, and magnesium.
- They are deficient in nitrogen, phosphorous, and organic matter.
- They are spread over the greater parts of Gujarat, Maharashtra, western Madhya Pradesh, northwestern Karnataka, Tamil Nadu, Rajasthan, Jharkhand.
They cover about 15 million hectares and account for 4.42 percent of the total reporting area.
- They are developed under arid and semi-arid conditions.
- They are found mainly in Rajasthan, west of Aravalli’s, northern Gujarat western part of Haryana, and southwestern part of Punjab.
- These soils contain a high percentage of soluble salts but have low moisture content and water-retaining capacity.
- On irrigation, they give good agricultural returns.
- They are mainly devoted to bajra, pulses, guar, fodder, and less water requiring crops.
- It covers about 12.2 million hectares accounting for about 3.7 percent of the total reporting area.
- Its name has been derived from the Latin word “Later” which means brick.
- These soils, when wet are soft and quite hard and cloddy on dying.
- These are the typical soils of monsoon climate.
- The soil is red in color due to the presence of iron oxide.
- It is developed mainly in the highland areas of the plateau.
- The soil is acidic in higher areas and less in the low-lying areas.
- The soil is rich in iron and aluminum, but poor in nitrogen, potash, potassium lime, and organic matter.
- They have low fertility but respond well to manuring and are mainly devoted to rice, ragi, sugarcane, and cashew nuts.
- They are found mainly in the hills of Western Ghats, Eastern Ghats, Chhattisgarh, Jharkhand, West Bengal, Assam, Garo hills of Meghalaya.
It covers about 18.2 million hectares or about 5.5 percent of the total reporting area of the country.
- These soils are generally immature and unsystematic.
- The color of soil is dark brown and the texture varies from silt loam to loam.
- These soils are found in the valleys and hill slopes of the Himalayas between 200 and 300 meters.
- They can be divided into loamy podzols and high-altitude soils.
- Podzols are acidic with low humus content and occupy the mid-latitude zone in the Himalayas.
- The High-altitude soils, depending on the forest cover, slope, and rainfall are classified as brown earth type and red loam.
- They occupy Assam, Darjeeling, Himachal Pradesh, and Jammu and Kashmir.
Red and Black Soils
- It is found in isolated patches in Bundelkhand, Rajasthan and Gujarat.
- They are less productive but perform well under irrigation.
- They are devoted to maize, bajra, millets, pulses, and oilseeds.
Grey and Brown soils
- They have been formed by the weathering of granite, gneiss, and quartzite.
- These are loose and friable soils.
- Due to the presence of iron oxide these soils vary from red to black to brown
- They are found in Rajasthan and Gujarat.
Sub montane Soils
- Formed by depositing eroded material from the Shiwaliks and the Lesser Himalayas.
- The soil is fertile and supports the luxuriant growth of forests.
- But clearing of forests for agricultural purposes has made this area highly susceptible to soil erosion.
- Found in Tarai region stretching from J & K to Assam in form of the narrow belt
Saline and Alkaline Soils
- The saline soils are characterized by the presence of sodium chloride and sodium sulphate.
- In these soils, the saline and alkaline efflorescence appear on the surface as a layer of white salt through capillary action.
- They are known by different names in different parts of the country. They are called relz, kallar, usar, rakar, thur, karl, and chapan.
- Found in Rajasthan, Haryana, Punjab, Uttar Pradesh, Bihar, and Maharashtra.
- Texture - sandy to sandy-loam.
- Deficient in nitrogen, calcium and have very low water-bearing capacity.
- These soils can be reclaimed by improving drainage, by applying gypsum and/or lime and by cultivating salt-resistant crops like barseem, dhaincha, and other leguminous crops.
Peaty and Marshy Soils
- They originate in the area of heavy rainfall where adequate drainage is not available.
- These are generally submerged during the rainy season and utilised for the cultivation of rice.
- These soils are rich in organic matter, highly saline, but deficient in phosphate and potash.
- These soils mainly occur in parts of the Kottayam and Alappuzha districts of Kerala and in the Sundarbans delta.
- They are also found in the deltas of Mahanadi, Godavari, Krishna, Kaveri, and the Ram of Kachchh.
- Karewas are the lacustrine (related to lakes) deposits in the Valley of Kashmir and in Bhadarwah Valley of the Doda District of the Jammu Division.
- These are the flat-topped mounds that border the Kashmir Valley on all sides.
- They are composed of fine silt, clay, sand, and bouldery gravel.
- They are characterized by fossils of mammals and at places by peat.
- The karewas have been elevated, dissected and in a great measure removed by subaerial denudation as well as by the Jhelum river giving them the present position.
- The karewas are mainly devoted to the cultivation of saffron, almond, walnut, apple and orchards.
- The karewas, devoted to saffron cultivation are fetching good income to the growers.
- The karewas of Palampur, Pulwama, and Kulgam are well known for their production of superior quality saffron.
- The area under snow and glaciers is about 4 million hectares.
- The high peaks of the Greater Himalayas, Karakoram, Ladakh, and Zaskar (Zanskar) are covered by ice and glaciers.
- The soils in these areas are immature, generally without soil erosion.
- It remains frozen and is unsuitable for the cultivation of crops.
Problems of Indian Soils
- The forces of nature often destroy the soil cover of an area.
- The process of soil destruction is the result of natural forces or can also be damaged and destroyed by human activities, such as deforestation, overgrazing of animals and unscientific use of agricultural land.
|Main Problems of the Indian soils|
- Soil erosion refers to the removal of topsoil.
- Soil erosion is a growing menace in many parts of India.
- When the topsoil is removed, it is known as sheet erosion, and when the runoff makes gullies, it is known as gully erosion.
- In India, soil erosion is a universal problem.
- In the areas where rainfall is heavy water is the main agent of soil erosion, while in the arid and semi-arid areas wind is responsible for soil erosion.
- According to one estimate, about 180 million hectares (about 60 percent of the total area of the country) is adversely affected by soil erosion.
- The main agents of soil erosion are water, wind, sea waves, glaciers, and shifting cultivation. Out of these, water is the most important agent of erosion.
A) It may be classified under three categories:
- surface erosion or the uniform removal of soil from the surface,
- Rill erosion in which the running water makes finger-shaped grooves in the land,
- gully formations, in which the rills are enlarged, making the land bad and unsuitable for cultivation.
- A typical example of gully erosion is provided in the Chambal valley in Madhya Pradesh. Rajasthan and Uttar Pradesh also provide typically examples of gully erosion.
- Gully erosion is also significant in the Shiwaliks tracts of Punjab, Haryana, Himachal Pradesh, Jammu and Kashmir, Uttarakhand, Uttar Pradesh and along the southern slopes of Himalayas, and the Western and Eastern Ghats.
- Wind erosion is significant in the arid and semi-arid areas of Rajasthan, Haryana, Punjab, western Madhya Pradesh and Gujarat.
- Wind erodes soil along the coastal plains of Peninsular India. Thousands of hectares of fertile lands of Uttar Pradesh, Gujarat, Haryana, Punjab, and western Madhya Pradesh have been adversely affected by this process.
- The tidal waters of the Arabian Sea and the Bay of Bengal cause considerable damage to the soils along with the coastal areas. Severe erosion of beaches along with Kerala, Tamil Nadu, Andhra Pradesh, Odisha, and Gujarat coasts is an example of sea-wave erosion.
- The worst affected areas of soil erosion include:
|I. Chambal and Yamuna rivers|
II. the southern slopes of Shiwaliks, Lesser and Greater Himalayas,
III. the Western and Eastern Ghats,
IV. the Chotanagpur Plateau, and
V. the arid and semi-arid areas of Rajasthan, Gujarat, Haryana, and Punjab.
Declining Soil Fertility
- Being utilised for centuries, and multiple cropping without fallowing the agricultural land, the natural fertility of the soil is depleting fast.
- The farmers use more inputs each subsequent year to get the return to the level of the previous year. This testifies to the diminishing fertility of the land.
- In fact, the unscientific rotation of crops (wheat and rice) over several decades has depleted the soil fertility in the Great Plains of India substantially. The cultivation of leguminous crops after a soil exhaustive crop can improve the soil fertility affected regions.
- An area is said to be waterlogged when the water table rises to the extent that soil pores in the root zone of a crop become saturated, resulting in the restriction of normal circulation of the air, the decline in the level of oxygen, and an increase in the level of carbon dioxide.
- Apart from soil erosion, there are many ill-drained, low lying areas in India where the soil has been damaged by waterlogging.
|Main Causes of Waterlogging|
(i) Seepage of water from canals,
(ii) Faulty on-farm water management,
(iii) Lack of drainage,
(iv) Interception of natural drainage,
(v) Indiscriminate cultivation in the bed of drainage channel, and
(vi) Inundation of marine delta cycles, and
(vii) Inundation in coastal areas during cyclonic storms.
Saline and Alkaline Soils
- Soil salinity and alkalinity are found in the relatively less rainfall recording areas where the rate of evaporation is generally higher than the rate of precipitation.
- They also develop in the Khadar lands and the canal irrigated areas.
- Under such conditions, the groundwater level rises and saline and alkaline efflorescence consisting of salts of sodium, calcium, and manganese appear on the surface as a layer of white salt through capillary action.
- According to one estimate, about 80 lakh hectares (2.4% of the country's reporting area) has been adversely affected by saline and alkaline
- The soils seriously damaged by the excess of calcium chlorides are found in the Rann of Kachchh.
- These soils are saline, marshy and infested with tall grasses, bushes and scrubs. They are almost useless from an agricultural point of view.
- A sound strategy needs to be developed to bring the salt flats under agriculture or pastures.
Consequences of Soil Erosion
- Loss of fertile topsoil from the top layer leading to gradual loss of soil fertility and agricultural productivity.
- Loss of important nutrients from the soil through leaching and water-logging.
- Lowering of the underground water table and decrease in soil moisture.
- Drying of vegetation and extension of arid lands.
- Increase in the frequency of droughts and floods.
- Silting of rivers and canal beds.
- Recurrence of landslides.
- Adverse effect on the economy which retards cultural development.
- Burden on the exchequer to reclaim the badlands.
- There is no uniform strategy to reclaim all the wasteland and degraded soils of different types. Some strategies that might help in the reclamation of wasteland are given below:
- All the degraded forest lands should be planted with trees. Marginal lands which are not suitable for agriculture should be brought under social forestry and agro-forestry.
- Degraded soils and degraded lands can be reclaimed with the help of watershed programmes.
- Rainwater harvesting and conservation should be the focus of development planning. A series of small projects of water harvesting in the watershed area should be undertaken to maximise benefits from watershed projects.
- Soil conservation practices should be adopted which have been briefly described in the following pages.
- If we look at the importance of soil resources for a country of over a billion people, we will find that judicious utilization and conservation of soil are of paramount importance.
- The farmers in the parched parts of Gujarat, Haryana, Rajasthan, and western Madhya Pradesh are successfully protecting their fields from soil erosion by planting rows of trees to reduce the velocity of winds which continually erode soil cover.
- Soil conservation includes a reduction in soil erosion, afforestation, rational utilisation of soils and ways to enhance their sustainability. Some of the important steps which can go a long way in the conservation of soils are as under:
- Soil erosion can also be reduced by plantation of trees. Trees reduce the intensity of runoff and increase the seepage of water to the underground water table.
- Social forestry can be developed along the banks of rivers, canals, lakes, roads, and railway tracks.
Restriction on the Felling of Trees:
- Apart from afforestation, it is equally important to check the indiscriminate felling of trees.
- People's awareness that resulted in the launch of the Chipko Movement can help in achieving this objective.
Contour Ploughing and Strip Cultivation
- In the hilly and mountainous areas, ploughing should be done according to the contours and not in an up-down direction of the slope.
- Contour ploughing is an effective way of checking soil erosion.
- Small strips can be developed on gentle slopes for sowing crops which help in overcoming the menace of soil erosion.
Control of Floods
- In India, the problem of soil erosion is majorly associated with floods. The floods generally occur during the rainy season. Therefore, efforts need to be made for the storage of floodwater or the diversion of additional rainwater.
- The inter-connecting of rivers as in the Garland Canal Project or the GangaKaveri Link Canal Project can be of immense help in this direction.
Reclamation of Ravine and Badlands
- Reclamation of gullies and ravines is also necessary to overcome the problem of soil erosion.
- Several such schemes involving plugging of gully mouths, construction of bunds across the gullies, levelling of gullies, afforestation, restriction on grazing is under implementation in the Chambal ravines of Madhya Pradesh, Uttar Pradesh, and Rajasthan.
Restriction on Shifting Cultivation
- In the states of northeast India and Western and Eastern Ghats, shifting cultivation (slash and burn) is one of the main causes of soil erosion.
- The shifting cultivators need to be persuaded to stop the practice of shifting cultivation and should be trained and motivated to adopt terraced fanning.
- A scheme to control shifting cultivation has been launched in the seven states of northeast India.
- This is a beneficiary-oriented programme that aims at the rehabilitation families of PI) the Jhumias (shifting cultivators).
- There is a need to extend this programme to other states of the tt) country and gradually replace this agricultural system with sedentary farming.
Restoration of Long Fallow
There are 96 lakh hectares 01 fallow lands. The old fallow land is mainly found in Andhra Pradesh, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan, Tamil Nadu, Bihar, Uttarakhand, and Uttar Pradesh. This old fallow land can be brought under cultivation, grazing and orchards which shall be helpful in the reduction of soil erosion.
Reclamation of Saline and Alkaline (usar) Soil
- The saline and alkaline affected area in the country is more than 80 lakh hectares. The state-wise distribution in the major states of India.
- This land needs reclamation. Application of cow-dung and gypsum are quite helpful in the reclamation of salt-affected soils.
Other Measures of Soil Conservation
- Construction of small dams across the tributaries of rivers in their upper reaches to control floods and soil erosion.
- Lining of canals to stop seepage of water which leads to waterlogging.
- Solving the problem of waterlogging by improving the surface and vertical drainage.
- Formation of windbreak and shelterbelts in arid and semi-arid regions.
- Increasing use of organic and compost manure.
- Popularizing the application of cow dung and green manure.
- Conversion of human waste and city garbage into manures.
- Scientific rotation of crops.
- Filling up gullies and forming terraces along the slopes.
- Levelling of ravines and planting of trees and grasses in the slopes.
- Check on shifting cultivation and conversion of jhum lands into sedentary agriculture.
- Promotion of afforestation in the degraded soils.
- Adopting the techniques of sustainable agriculture.
- To educate the public about the adverse effects of soil erosion through seminars, conferences, and workshops in the regions of degraded soils.
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