soils. - ias junior · • soil particles move in three ways, depending on soil particle size and...

Beginner Module – Indian Geography: Soils

W W W . I A S J U N I O R . C O M P a g e 1 | 27

SOILS.

What is Soil?

Soil can be simply defined as a mixture of small rock particles/debris and organic materials/

humus which develop on the earth surface and support growth of plants.

Soil Classification

• In India, soil had been classified from the ancient period itself even though it was not as

detail as the modern classifications.

• In the ancient period, the classification was based on only two things; whether the soil is

fertile or sterile. Thus the classification were:

1. Urvara [fertile]

2. Usara [sterile]

Agencies involved in soil classification:

• In the modern period, when men started to know about the various characteristics of soil

they began to classify soil on the basis of texture, colour, moisture etc.

• When the Soil survey of India was established in 1956, they studied soils of India and

their characteristics.

• The National Bureau of Soil Survey and the Land Use Planning, an institute under

the control of Indian Council of Agriculture Research did a lot of studies on Indian soil.

Major classification of Indian soil:

1. Alluvial soil [43%]

2. Red soil [18.5%]

3. Black / regur soil [15%]

4. Arid / desert soil

5. Laterite soil

6. Saline soil

7. Peaty / marshy soil

8. Forest soil

9. Sub-mountain soil

10. Snowfields

http://www.iasjunior.com/



Classification of soils:

Alluvial soil:

• Mostly available soil in India (about 43%) which covers an area of 143 sq.km.

• Widespread in northern plains and river valleys.

• In peninsular-India, they are mostly found in deltas and estuaries.

• Humus, lime and organic matters are present.

• Highly fertile.

• Indus-Ganga-Brahmaputhra plain, Narmada-Tapi plain etc are examples.

• They are depositional soil – transported and deposited by rivers, streams etc.

• Sand content decreases from west to east of the country.

• New alluvium is termed as Khadar and old alluvium is termed as Bhangar.

• Colour: Light Grey to Ash Grey.

• Texture: Sandy to silty loam or clay.

• Rich in: potash, Poor in: phosphorous.

• Wheat, rice, maize, sugarcane, pulses, oilseed etc are cultivated mainly.

Red soil:

• Seen mainly in low rainfall area.

• Also known as Omnibus group.

• Porous, friable structure.

• Absence of lime, kankar (impure calcium carbonate).




• Deficient in: lime, phosphate, manganese, nitrogen, humus and potash.

• Colour: Red because of Ferric oxide. The lower layer is reddish yellow or yellow.

• Texture: Sandy to clay and loamy.

• Wheat, cotton, pulses, tobacco, oilseeds, potato etc are cultivated.

Black soil / regur soil:

• Regur means cotton – best soil for cotton cultivation.

• Most of the Deccan is occupied by Black soil.

• Mature soil.

• High water retaining capacity.

• Swells and will become sticky when wet and shrink when dried.

• Self-ploughing is a characteristic of the black soil as it develops wide cracks when

dried.

• Rich in: Iron, lime, calcium, potassium, aluminum and magnesium.

• Deficient in: Nitrogen, Phosphorous and organic matter.

• Colour: Deep black to light black.

• Texture: Clayey.

Laterite soil:

• Name from Latin word ‘Later’ which means Brick.

• Become so soft when wet and so hard when dried.

• In the areas of high temperature and high rainfall.

• Formed as a result of high leaching.

• Lime and silica will be leached away from the soil.

• Organic matters of the soil will be removed fast by the bacteria as it is high temperature

and humus will be taken quickly by the trees and other plants. Thus, humus content is

low.

• Rich in: Iron and Aluminum




• Deficient in: Nitrogen, Potash, Potassium, Lime, Humus

• Colour: Red colour due to iron oxide.

• Rice, Ragi, Sugarcane and Cashew nuts are cultivated mainly.

Desert / arid soil:

• Seen under Arid and Semi-Arid conditions.

• Deposited mainly by wind activities.

• High salt content.

• Lack of moisture and Humus.

• Kankar or Impure Calcium carbonate content is high which restricts the infiltration of

water.

• Nitrogen is insufficient and Phosphate is normal.

• Texture: Sandy

• Colour: Red to Brown.

Peaty / marshy soil:

• Areas of heavy rainfall and high humidity.

• Growth of vegetation is very less.

• A large quantity of dead organic matter/humus which makes the soil alkaline.

• Heavy soil with black colour.




Forest soil:

• Regions of high rainfall.

• Humus content is less and thus the soil is acidic.

Mountain soil:

• In the mountain regions of the country.

• Immature soil with low humus and acidic.

Saline (Usara)




• Areas of Arid and semiarid region -Water logged swamps -West Gujarat, Deltas of East

coast, Sunderbans, Punjab, Harayana, Uttar Pradesh, Bihar

• Rich in Sodium, Potassium, Magnesium,

• Poor in Nitrogen Calcium

• Characteristics

o More salts because of dry climate and poor drainage -White incrustation of

calcium, magnesium and sodium salts on surface

o Infertile- does not support vegetative growth

o Sandy to loamy structure -Seawater intrusions in deltas promote salinity

o Intense cultivation with excessive use of irrigation has made alluvial soil saline

o Excessive irrigation with dry climate promotes capillary action, thus salt

deposits on topsoil Gypsum is added to solve salinity problems




SOILS - MINDMAPS




Distribution of soil in India.




SOIL EROSION • Destruction of soil cover and subsequent washing down is soil erosion -

• Soil formation and erosion occur simultaneously with a balance.

• Sometimes, such balance is disturbed by natural or human factors, leading to greater

removal of soil

• Causes of soil erosion:

• Human induced:

o Deforestation, overgrazing, overuse of chemical fertilisers, construction, mining,

defecting methods of farming

• Natural:

o Wind, water(gullies Badland/Ravines; Sheet erosion), glacier, rain wash,

landslides, flood -

• Soil erosion involves-

o Detachment,

o Movement and

o Deposition of soil particles

Effects of soil erosion:-

• Reduces cropland productivity,

• Pollution to adjacent watercourses, wetlands and lakes

• Soil compaction,

• Low organic matter,

• Loss of soil structure,

• Poor internal drainage,

• Salinization and

• Soil acidity; are other serious soil degradation conditions that can accelerate soil erosion

process

NATURAL METHODS OF SOIL EROSION

WIND:

• Occurring in mostly flat, barren areas;

• dry and sandy soils or any soil area which is loose, dry and finely granulated.

• Soil particles move in three ways, depending on soil particle size and wind strength-

Suspension, Saltation and surface creep.

• Lack of windbreaks (trees, shrubs, crop residue), lack of permanent vegetative cover,

soil surface roughness due to faulty tillage practices, changes in climate cause wind

erosion.




WATER:

• Surface water runoff occurs when there is excess of water on slope that cannot be

absorbed into the soil or trapped in the surface.




HUMAN INDUCED METHOS OF SOIL EROSION:

Deforestation:

• Plants are cut. No strong binding of soil. Loss of fertile soil

Overgrazing

• Over grazing in forests destroy newly regenerated groeth.it also makes soil more

compact and impervious

• Reduces: - Ground cover, - Ability of water penetration - Survival of soil organisms to

provide minerals




Overuse of agrochemicals

• Pesticides and fertilizers increase yield but overuse changes soil composition and

balance of microorganism in the soil. Stimulates growth of harmful bacteria at expense

of beneficial kinds

Tillage practices

• Ploughing up and down the slope is defective method of farming.

• Redistribution of soil through tillage causes down-slope movement of soil, causing

severe loss of upper soil. Promotes water erosion

Agriculture

• Natural vegetation replaced with agricultural fields exposes topsoil and dries it out.

• Diversity and quantity of microorganism to keep soil fertile may decrease and wash out

important nutrients either by wind or water.

Coastal erosion

• Natural factors like cyclone, waves and tides as well as anthropogenic activities like

human settlements resulted in loss of mangroves and coastal vegetation.




Soil conservation methods

Afforestation:

• It includes the prevention of forest destruction along with growing new forests or

increase area under forests.

• A minimum area 20 to 25 per cent of forest land was considered healthy for soil and

water conservation for the whole country.

• It was raised to 33 per cent in the second five year plan – 20 per cent for the plains and

60 per cent for hilly and mountainous regions.

Dams

• Much of the soil erosion by river floods can be avoided by constructing dams across the

rivers in proper places. This checks the speed of water and saves soil from erosion.

• But indiscriminate dam construction can worsen the condition by creating floods and

landslides like it happens in the Himalayan region.

Agricultural practices:




Wind breaks:

Shelter belts or Windbreaks

• In the coastal and dry regions, rows of trees are planted to check the wind movement to

protect soil cover.




Sand fences

• Sand fences are barriers made of small, evenly spaced wooden slats or fabric. They are

erected to reduce wind velocity and to trap blowing sand. Sand fences can be used as

perimeter controls around open construction sites to keep sediments from being blown

offsite by the wind.

Structural solutions for soil conservation:

Retaining walls

• Holds soil sliding away from structure.




Stone pitching

• Vegetation inter-planted between stones Generally used on steep slopes for upland

paths Provides a sustainable surface that can withstand flowing water on top

Wire netting

• Low netting that slows or traps run-off water and become a productive vegetative belt

across degraded area.

COASTAL AREAS—

Tetra pods

• Dissipate force of incoming waves by making water flow around them rather than

against them. Due to their design, they remain stable even under extreme climatic




conditions. Together they form interlocking and porous barrier to dissipate waves and

currents

Groyne

• Embankment type structures Constructed transverse to river flow to protect bank by

deflecting current away from bank




SOIL SALINITY AND ALKALINITY

• In Saline and Alkaline Soils, the top soil is impregnated (soak or saturate with a

substance) with saline and alkaline efflorescences (become covered with salt particles).

• Undecomposed rock fragments, on weathering, give rise to sodium, magnesium and

calcium salts and sulphurous acid.

• Some of the salts are transported in solution by the rivers.

• In regions with low water table (due to over irrigation in canal irrigated areas), the salts

percolate into sub soil and in regions with good drainage, the salts are wasted away by

flowing water.

• But in places where the drainage system is poor, the water with high salt concentration

becomes stagnant and deposits all the salts in the top soil once the water evaporates.

• In regions with high sub-soil water table, injurious salts are transferred from below by

the capillary action as a result of evaporation in dry season.

• In canal irrigated areas plenty of the water is available and the farmers indulge in over

irrigation of their fields.

• Under such conditions, the ground water level rises and saline and alkaline

efflorescences consisting of salts of sodium, calcium and magnesium appear on the

surface as a layer of white salt through capillary action.

• Alkalinity implies the dominance of sodium salts, specially sodium carbonate.

• Although salts of alkali are somewhat different in their chemical properties from the

salts of saline soils both soils occur in the same areas.

• Sandy soils are more prone to alkalinity and the loamy soils to salinity-alkalinity.

• It is estimated that about 80 lakh hectares of land (2.43% of the country’s total area) is

affected by the problem of salinity and alkalinity.

• Vast tracts of canal irrigated areas in Uttar Pradesh. Punjab and Haryana; arid regions of

Rajasthan, semi-arid areas of Maharashtra, Gujarat, Andhra Pradesh, Telangana and

Karnataka etc. are facing this problem.

• Although Indira Gandhi canal in Rajasthan has turned the sandy desert into a granary, it

has given birth to serious problems of salinity and alkalinity.

• Effects of salinity and alkalinity

• Salinity and alkalinity have adverse effect on soil and reduce soil fertility.

• Cultivation is not possible on saline soils unless they are flushed out with large

quantities of irrigation water to leach out the salts.

• Choice of crops is limited to salinity tolerant crops like cotton, barley etc..

• Quality of fodder and food produced in poor in quality.

• Salinity and alkalinity create difficulties in building and road construction.

• These cause floods due to reduced percolation of water.




Steps to treat Salinity and Alkalinity

• Leaching

o Additional water on soil percolates down into ground, taking salts with it;

though it shouldn’t be in excess

• Regular vegetation canopy and litter reduces evaporation

• Addition of organic matter and its deep root penetration improves soil structure and

endures good drainage

• Maintaining low water table by not over irrigating.

• Usage of artificial drainage system, whenever required

• French drains

o A ditch like trench is filled with rock/gravel with pipe at bottom- Catches water

runoff and directs it away from structure that can be damaged

• Scrapping

o Removing accumulated salts on the surface by mechanical means Helps in

temporary improvement of crop growth, but disposal of salts is a major problem

• Flushing

o Washing away the accumulated salts by flushing water over the surface. The

amount of salts to be flushed away is very small, hence this method doesn’t have

much practical significance Providing outlets for lands to drain out excess water

and lower water table.

• Seal leakages from canals, tanks and other water bodies by lining them.

• Making judicious use of irrigation facilities.

• Crop rotation.

• Liberal application of gypsum to convert the alkalies into soluble compounds.




• Alkali can be removed by adding sulphuric acid or acid forming substances like sulphur

and pyrite.

• Organic residues such as rice husks and rice straw can be added to promote formation of

mild acid as a result of their decomposition.

• Flushing the salt by flooding the fields with excess water. However, this practice can

lead to accumulation of saline water in the downstream area.

• Desertification

• The United Nations Convention to Combat Desertification (UNCCD) defines the tem

desertification as ‘land degradation in arid, semi-arid and sub-humid areas resulting

from various factors including climatic variations and human activities’ Desertification

is a process of land-degradation by which a region becomes progressivly drier and drier-

eventually transforming into a desert.

• Desertification is the spread of desert like conditions in arid or semi-arid areas due to

man’s influence or climatic change.

• A large part of the arid and semi-arid region lying between the Indus and the Aravali

range is affected by spreading desert conditions.

• Desert soils suffer maximum erosion by wind. The sand carried by wind is deposited on

the adjoining fertile lands whose fertility dwindles and slowly the fertile land start

merging with the advancing desert.

• It has been estimated that the Thar Desert is advancing at an alarming rate of about 0.5

km per year.

• The process of desertification is attributed to uncontrolled grazing, reckless felling of

trees and growing population. Climate change have also contributed to the spread of

deserts.

Ecological implications of desertification • Drifting of sand and its accumulation on fertile agricultural land.

• Excessive soil erosion by wind and to some extent by water.

• Deposition of sand in rivers, lakes and other water bodies thereby decreasing their water

containing capacity.

• Lowering of water table leading to acute water shortage.

• Increase in area under wastelands.

• Decrease in agricultural production.

• Increase in frequency and intensity of droughts.

Measures of Controlling Desertification

• Intensive tree plantation in the transition zones.

• Mulching shifting sand dunes in deserts with different plant species. Mulches serve as

an effective physical barrier to the moving sand.

• Grazing should be controlled and new pastures should be developed.

• Indiscriminate felling of trees should be banned.




• Alternative sources of fuel can reduce the demand for fuelwood.

• Sandy and wastelands should be put to proper use by judicious planning.




Water logging • The flat surfaces and depressions results in waterlogging.

• Waterlogged soils are soaked with water accumulated during rainy season or due to

leakage from various water sources.

• Extent of waterlogged soils is about 12 million hectares in India – half of which lies

along the coast and the other half in the inland area.

• Waterlogging is believed to be one of the chief causes of salinity.

• Proper layout of drainage schemes is the only way to overcome the menace of

waterlogging.

• The basic methods of removing excess water from waterlogged soils are

(a) surface drainage

▪ Surface drainage involves the disposal of excess water over ground

surface through an open drainage system with an adequate outlet

(b) vertical drainage.

▪ Vertical Drainage. Any bore or well from which the underlying water

is extracted is defined as vertical drainage. It works well in Indo-

Gangetic plain where the pumped water is used for irrigating the

neighboring regions.




SOIL POLLUTION

Soil pollution- When humans introduce harmful objects, chemicals or substances, directly or

indirectly into soil in a way that causes harm to other living things or destroys soil or water

ecosystems.

Soil Pollutants-




REASONS

• Construction sites- presence of various chemicals that gets mixed with soil

• Industrial activities- Amount of mining and manufacturing has increased rapidly.

Industrial waste (by-products of industrial activities lingers) in soil as they are not

disposed of, in a safe manner

• Agricultural activities- Increased use of pesticides and fertilizers has polluted the soil

with chemicals—they seep into ground, mix with water and reduce soil fertility.

• Waste disposal- Biological or industrial waste is not disposed in efficient manner; Land

fill sites are creating soil pollution.

• Non-biodegradable materials- Soil is continuously exposed to plastic which is non-

biodegradable—releases toxins over period of time which harms the soil fertility.

• Accidental spills- During storage or transportation, accidental oil spills occur which has

the potential to harm the soil through chemicals present within it.

• Acid rains- The polluted rains when mixes with soil, it dissolves important nutrients

and thus, changes the structure of soil as well as reduces its productiveness.

EFFECTS:

• Health risks- People living near polluted lands have higher incidences of small and

terminal illness, children often suffer from development problems and weakened

immune systems




• Effect on growth of plants- Ecological balance gets affected due to widespread

contamination of soil. Plant unable to adapt to changing soil structure and chemicals

present within. Such widespread contamination may lead to famines in longer run.

• Decreased soil fertility- The toxic chemicals present in soil decreases soil fertility and

thus decrease soil yield.

• Toxic dusts- Toxic dusts and foul gases emanating from land fill sites pollutes the

environment and causes serious health effects on people and animals Changes in soil

structure- Death of important organisms of soil may change the soil structure.

SOLUTIONS

• Pollution Regulation- Strict pollution regulation levels for industries

• Safe disposal- Proper disposal of industrial and agricultural waste

• Waste management- Waste management projects should be scientifically carried out

• Organic farming

• Recycling- Recycling paper, plastic and other materials reduces burden on soil

• Reuse- Reusing materials instead of ‘use and throw’

• Plantation- Encouraging small plants plantation programmes.


soils. - ias junior · • soil particles move in three ways, depending on soil particle size and...

Documents