SOILS

SOILS

• 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.
• Soils are the mixture of minerals, organic matter, gases, liquids, and the countless organisms that supports life on earth.
• Soil is the natural body known as ‘Pedosphere’
• Soil is considered to be the “Skin of Earth”.
• Soils have the mean Prokaryotic density of roughly 1013 organisms per cubic meter.

The Indian Council of Agricultural Research classified Indian Soils into 9 categories

The major soil groups are as follows

1. Alluvial Soil
2. Black Soil
3. Red Soil
4. Laterites and Laterite Soil
5. Forest Soil
6. Saline and Alkaline Soil
7. Peaty and other Organic Soil

ALLUVIAL SOIL

• From agricultural point it is most important soil found in India
• Covers about 24% of land’s surface
• Composed of sediments deposited by rivers and waves.
• Occupy great plains from Punjab to Assam.
• Occurs in valleys of Narmada, Tapti, Mahanadi, Godavari, Cauvery.
• Geologically it is divided into
  1. Khadar ( New Alluvium)
  2. Bangar (Old Alluvium)
• Doesn’t have recognizable horizons and in some portions it is covered by unproductive loess deposits
• Usually deficient in nitrogen & humus content and this necessities repeated additions and manure and fertilizers
• Suitable for cultivation of all types of crops depending upon the climate suitability.

BLACK SOIL

• Second major group of soil found in India
• Ideal for the cultivation of cotton crop due to higher moisture retention capacity, which means it doesn’t require much irrigation
• Frequently refered as Black cotton soil and covers large tracts of Deccan plateau
• Crops like sugarcane, citrus fruits, banana also grew well on this type of soil.
• This soil classified as chernozem locally known as regular soil
• Covers large areas in Maharashtra, Gujarat, Madhya Pradesh, Karnataka, Andhra Pradesh, Tamil Nadu.
• Black colour is due to presence of Iron and Aluminium
• It will become sticky when wet and develops cracks when dry.
• It’s level of fertility is well accepted

Characteristics of Black Soil

• Clayey, deep and impermeable. They swell and become sticky when wet and shrink when dried
• During dry season, these soils develop wide cracks. Rich in lime and iron, magnesia and alumina. Also contain potash. Lack Phosphorus, nitrogen and organic matter
• Very clayey and therefore highly retentive of water. Because of high clay content, these soils expand when wet and become difficult to plough.
• During dry season, black soils shrink and develop big cracks which help in air circulation.
• Dark in colour, suitable for cotton cultivation are residual soils.
• Spread over an area of 5.4 sq. km., i.e. 16.6 % of the total land area of the country

RED SOIL

• Third major soil group and covers the peninsular region reaching upto Rajmahal hills in the East, Jhansi in North, Kutch hills in West.
• Surrounds black soil on east, southeast and north
• Generally porous and contain soluble salts and lime in small proportions.
• Suitable for cultivation of rice, ragi, tobacco, vegetables.
• Groundnuts and potatoes grown at higher elevations

Characteristics of Red Soil

• Red soils are reddish in colour due to the presence of iron. Formed due to weathering of ancient crystalline and metamorphic rocks.
• Parent rocks are acid granites and gneisses. Occupy an area of about 3.5 lakh sq km – 10.6% of the total land area of the country.
• These are transported type soils. Are mostly light to dark colour depending on new or old alluvium.
• Rich in potash and become fertile with the proper use of fertilizers and irrigation.
• Deficient in nitrogen,lime, magnesia, humus and phosphate. Red due to its very high iron content.
• Are porous, friable in nature . Loose and aerated. Contains soluble salts in small quantities.

LATERITES AND LATERITE SOIL

• Formed through the porous of Laterisation
• Contain Iron oxides which impart a red color to soil
• Soil occurs in higher reaches of Sahyadris, eastern ghats, Rajmahal hills, Higher areas of peninsular region
• Also found on lower parts of kerala as well as pockets of Orissa, West Bangal, Assam
• Generally poor in humus, nitrogen and soluble salts due to heavy leaching.
• Suitable for rice, ragi cultivation if manure is applied regularly.

FOREST SOIL

• Forest and hilly areas are covered by forest soil.
• Rich in organic matter but varies character according to relief conditions.
• Himalayas other ranges in north, higher reaches of hills in south, peninsular region have this soil.
• It is deficient in Potash, Phosphorous, Lime.
• Need continued use of fertilizers for good yields.
• Plantation of tea, coffee, spices and tropical fruits are laid or cultivated in this soil.

ARID AND DESERT SOIL

• Covers northwestern parts of country.
• Entire area to the west of Aravallies in Rajasthan and parts of Haryana, Punjab and Gujarat.
• Rich in phosphates but poor in nitrogen and organic matter.
• Due to lack of water and sandy texture soils of this group are considered poor.
• They prove quite fertile if irrigation facilities are provided and organic manure regularly.

SALINE AND ALKALINE SOILS

• Many parts of arid and semi-arid areas of Rajasthan, Punjab, Haryana, Uttar Pradesh, Bihar have saline and alkaline
• Effervescences mainly of sodium, calcium and magnesium
• They are called Reh, kallar, Usar and are infertile
• Salts are usually confined to upper layers and soils can be reclaimed by Improving drainage
• Alkaline soils can be reclaimed by application of gypsum also

PEATY AND OTHER ORGANIC SOIL

• This soil contain high accumulation of organic matter and considerable amount of soluble salts.
• This soil is highly saline rich in organic matter but deficient in phosphorous and potash.
• Found in kottayam and alleppey dist (Kerala).
• Marshy soils found in coastal areas of Orissa, West Bengal, Tamil Nadu, Central and Northern Bihar, Almora dist ( Uttarkhand).
• It is not conducive to cultivation

SOIL EROSION

Soil erode- when topmost fertile layer of the soil become loose and gets eroded/washed away with the action of wind or water.

Common Causes

1. Deforestation
2. Over-grazing
3. Action of wind, water, glacier, etc.
4. Faulty methods of agriculture, over-irrigation, shifting agriculture, wrong ploughing, etc.
5. Other anthropogenic factors(mining activities,industrial activities,etc).

CAUSES OF SOIL EROSION IN INDIA

Heavy population pressure on land - forest cover as low as 20.55% of total area – population continues to rise at a rapid rate – more forests are destroyed – heavy pressure on land.

Nature of Rainfall- receives 80 to 90 per cent of rainfall in the monsoon season. – heavy downpour during during monsoon months causes floods. - remaining months – droughts – these affect soils.

Overgrazing – number of domestic animals, esp cattle highest in world – cattle freely graze in open lands making them bare of vegetation-winds carry away dry soil particles – Rajasthan

Bad farming techniques – plough fields in traditional ways – small size of hholdings, absence of terracing, contour cultivation, crop rotation, improper use of manure have caused erosion

Topography – North –Eastern parts of India, Shiwaliks and the hilly regions in south India are affected by soil erosion because of steep slopes and heavy rainfall. During heavy rainfall, soils are washed away by running water down the slope.

Deforestation - destruction of forests for cultivation – cutting of trees exposes the soil to water and wind which leads to soil erosion

REGIONS OF SOIL EROSION

• Rajasthan
• Madhya Pradesh
• Maharashtra
• Uttar Pradesh
• Gujarat
• Andhra Pradesh
• Karnataka

Worst affected areas include

• The badlands of Chambal and Yamuna rivers
• The Piedmont zone of the western Himalayas
• The Chotanagpur plateau region
• The Tapi-Sabarmati valley region in Gujarat
• The Regur soil area of Maharashtra
• The dry areas of Rajasthan, Gujarat and Haryana

EFFECTS OF SOIL EROSION

1. Loss of fertile top soil
2. Lowering of the underground water table and decreasing soil moisture
3. Drying of vegetation and extension of arid lands, increase in the frequency of droughts and floods
4. Silting of river and canal beds, Recurrence of landslides, adverse effect on economic prosperity and cultural development
5. Wind erosion reduces the productive capacity of soil, as most of the nutrients required by the plants are carried by the wind.

PREVENTION OF SOIL EROSION

Terrace Farming- On hilly slopes, terraces act as bunds and prevent the soil from being washed away.

Contour ploughing- Ploughing along contourson a slope prevents soil being washed away by rainwater or by surface run off. Contours act like bunds. Terraces are levelled into step like small fields with even slope.

Afforestation - planting of trees along the edges of the fields, the waste land and on steepy slopes to prevent soil erosion as wells to enahance the capacity of the soil to retain water. Increase area under forests and indiscriminate felling of trees must stop.

Shelter Belts - Farmers plant trees in several rows to check wind erosion. Known as wind breaks.

Strip cropping - Crops are grown in alternate strips of land to check the impact of the winds.

Construction of dams - Rivers cause 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.

Ploughing Gullies - The gullies made in the soil are plugged with deposition of silt during heavy rains.

Shifting or Jhuming - or slash and burn type of agriculture should be banned.