Soils in India

• Soil is the uppermost layer of Earth’s crust.
• Soil is the medium in which plants grow and thus it supports the lives on earth.
• A number of factors contribute to the soil formation and fertility viz.

The soils of India on the basis of their formation are divided in the following two broad categories viz. 

• Residual Soil → Which form at the place of their origin for ex. Black soils
• Transported Soil → Which are transported from place of their formation for ex. Alluvial soils

Types of Soils Found in India

Alluvial Soil

• Formed by depositional work of rivers valleys, flood plains & deltas
• Highly fertile Riverine soils → Transported type
• Largest Tract → Satluj Ganga Plains
• Less connection with Parent material
• Rich in Potash but deficient in Nitrogen & Humus content
• Good for both rabi and kharif crops
• In delta region, they are ideal for jute cultivation
• Best for cereals & Pulses
• Khadar → Deposited by flood annually (Fresh silt) → non porous, clayey and loamy
• Bhangar → Above flood level; well drained & drier → coarse in nature, contain kankar (lime nodules), pebbles, gravels
• Forms 22.16 % of the total land area of the country

Black Soil

• Formed By solidification of Lava
• Mainly found in Deccan Plateau
• Also known as black cotton soil or Regur soil
• Black colour is due to its iron content, derived from plutonic lava materials
• Highly fertile (< Alluvial)
• Residual type of Soil
• Deficient in organic content, phosphorus, nitrogen
• Rich in lime and iron, magnesia and alumina; also contains Potash
• Highly clayey and impermeable → Highly moisture retentive
• Ploughed in dry season as on evaporation cracks develop for better seed penetration
• Regions → Maharashtra, Gujrat, Madhya Pradesh, Andhra Pradesh, Parts of Tamil Nadu
• Forms 16.6 % of the total land area of the country

Red & Yellow Soil

• Formed by weathering of Igneous (crystalline) & metamorphic rocks
• Less fertile than Alluvial & Black soils
• Lacks water retentive capacity
• Reddish in color due to presence of Feo (Ferrous oxide)
• Looks Yellow in Hydrated form
• Transported type of soil
• Deficient in nitrogen, lime, magnesia, humus and phosphate
• Rich in potash and become fertile with the proper use of fertilizers and irrigation
• Are porous, aerated & friable in nature
• Regions → Periphery areas of Deccan Plateau viz. Chhotanagpur plateau, Telangana, Nilgiris, Tamil Nadu, Karnataka, Andhra Pradesh
• Suitable for the cultivation of millets, pulses, Linseed, tobacco etc.
• Forms 10.6% of the total land area of the country
  

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Laterite Soil

• Formed under conditions of high temperature and heavy rainfall with alternate wet and dry periods.
• Thus its formation takes place strictly under monsoon conditions
• Formed by leaching away of siliceous matter
• With rain, Lime & Silica leaches away, leaving insoluble Feo & Al compounds → Desilication
• Humus content of soil is fast removed by bacteria which thrive well in high temp.
• Residual type of soils, formed by leaching in areas of heavy rain
• Mainly found in Highland or Plateaus with heavy rainfall
• Not useful for agriculture except for plantation crops like Tea, Rubber, Coffee & Cashews
• Used as building material & in making bricks
• Are of Coarse texture with soft & friable nature
• Poor in Lime, Nitrogen, Magnesium & Humus content; Rich in Feo & Alumina
• Regions → Meghalaya, Karnataka, Kerala, Tamil Nadu, hilly regions of Assam, Rajmahal hills and Chhota Nagpur plateau
• Forms 7.2 % of the total land area of the country

Saline / Alkaline Soil

• Found in arid or semi-arid conditions along with water logged areas
• Highly saline due to dry climate, poor drainage & high evaporation
• Infertile & does not support vegetative growth
• Found at Bihar, Rajasthan, UP., Punjab, Haryana, Maharashtra
• Salinity also Caused due to excessive irrigation in dry conditions which promotes capillary action

Arid Soil

• Found in areas with rainfall < 50 cm
• Sandy, porous, coarse & rich in salts
• Generally saline due to high evaporation
• Covered with thick brown mantle which inhibits soil growth
• Originated from the mechanical disintegration of the ground rock of by deposition by wind
• Low rainfall and high temperature are reasons for the formation of this soil
• Mainly in SW Haryana & Punjab and W – Rajasthan
• Actually fertile, water being the only limiting factor
• Cereals grown are Jowar, Bajra, Ragi & Oil seeds → Drought resistance crops
• Forms 3.9 % of the total land area of the country

Mountain Soils

• Prone to soil erosion → top soil getting washed away due to the steep slopes of the mountains after a heavy rainfall
• These soils are mostly thin and infertile
• Include peat, meadow and forest hill soils
• Rich in humus but deficient in potash, phosphorous and lime
• Generally loamy & silty on valley side and coarser in upper slopes
• Useful for Tea, coffee, spices and tropical fruits
• Regions → Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Assam, Sikkim, Arunachal Pradesh

Peaty / Organic Soil

• Found in high rainfall + high humid areas of WB, Orissa & Kerala
• Rich in Humus & organic content, sometimes alkaline too
• Heavy, Dark & acidic

Salinity of Soils

• Predominance of Chloride & sulfates of N, Ca & Mg, Esp. of NaCO3
• Decreases soil fertility, Quality of fodder becomes poor, Difficulties in Housing & road construction
• Addition of Gypsum (Converts Alkalis to compounds), Addition of rice husk & rice straw also counters alkalinity by forming light acids
• Crop rotation involving Daincha (Green Fodder) also counters salinity.

Prevention of Soil Erosion Techniques

Terrace Farming

• On hilly slopes, terraces act as bunds and prevent the soil from being washed away
• Farming is done on a unique step like structure and the force of water running off is slowed down
• Terraced farming is more common on small farms and in underdeveloped countries, since mechanized equipment is difficult to deploy in this setting

Contour ploughing

• Land should never be ploughed up & down as it increases erosion
• Ploughing along contours on a slope prevents soil being washed away by rainwater or by surface run off
• Contours act like bunds and thus prevents soil erosion by allowing water to slowly penetrate the soil
• Terraces are levelled into step like small fields with even slope

Contour barriers / Contour trenching

• Contour strips which intercept downslope flowing water and soil particles
• Several 2 feet by one-foot trenches are formed across the slopes at suitable intervals
• Tree seedlings are to be planted above the trench
• These barriers slow down the water movement and reduce its erosive force
• They also filter out and trap many of the suspended soil particles, keeping them from being washed out of the field

Afforestation

• Planting of trees along the edges of the fields, the waste land and on steep slopes to prevent soil erosion
• Also to enhance the capacity of the soil to retain water

Shelter Belts

• A line of trees or shrubs planted to protect an area, especially a field of crops, from fierce weather
• Farmers plant trees in several rows to check wind erosion
• Also known as wind breaks

Cover crops / Crop rotations

• Cover crops such as legumes, white turnip, radishes and other species are rotated with cash crops to blanket the soil year-round
• Act as green manure that replenishes nitrogen and other critical nutrients
• Also help suppress weeds & increase soil fertility.

No-till farming

• Also, called zero till age or direct drilling
• A way of growing crops or pasture from year to year without disturbing the soil through tillage
• Increases the amount of water that infiltrates into the soil
• Also increases organic matter retention and cycling of nutrients in the soil
• keeps soils anchored in place rather than having bare ground exposed to wind and water

Strip Cropping

• Crops are grown in alternate strips of land to check the impact of the winds.
• It is used when a slope is too steep or when there is no alternative method of preventing soil erosion.
• Contour strip cropping → Cultivation of soil protecting crops in strips alternating with erosion permitting crops. The strips should be across the slope.
• Field strip cropping → Plants are cultivated in parallel strips across the slopes

Mulching

• Mulches are materials placed over the soil surface to maintain moisture and improve soil conditions
• A protective layer of a material that is spread on top of the soil
• Mulches can either be organic — such as grass clippings, straw, bark chips, and similar materials
• Or inorganic — such as stones, brick chips, and plastic

Construction of Dams

• Rivers causes soil erosion
• Dams are built in the upper course of rivers to control erosion of soil
• This would check the speed of water and thereby save soil from erosion