Introduction

Soils with different layers have different physical and chemical properties. Topmost layer is humus or organic matter, topsoil followed by transition zone, sub soil, weathered rock material and parent rock. In soil erosion topsoil is lost. Subsoil can’t support plant life.

 

Soil nutrients:

 

  1. Air – carbon, oxygen

 

  1. Water – hydrogen, oxygen
  2. Soil:
  3.     Macronutrients: nitrogen, phosphorous, potassium, calcium, magnesium, sulphur
  4.  Micronutrients: Boron, chlorine, iron, magnesium, iron, copper.

 

Ideal ratio of N, P and K should be 4:2:1 but India its 8:4:1. Urea is out of Nutrient based subsidy and so is misused. Due to the high misuse of urea there is nitrate pollution in ground and water.

 

Soil health card are issued by the government for providing information on the nutrient status of the soil and recommendation on appropriate dosage of nutrients.

 

Implications:

 

  1. Soil and water pollution.
  2. Eutrophication of lakes.

 

  1. Nitrate poisoning in ground water leads to stomach cancer
  2. Without humus, chemicals harden the soil and make it infertile.

 

Organic farming:

 

  1. Paramparagat krishi vikas yojana to promote organic farming, discourage use of chemicals as inputs and promote bio-fertilizers, vermin compost, sustainable practices like crop rotation, water efficiency.
  2. Green manure are sowing of crop seeds, sun hemp and guar then mulching and ploughing them into soil to enrich N, P in the soil.

 

Vermi compost:

 

Mixture of earthworms and organic waste. The earthworms break down the matter to give nutrient rich, water soluble, moist organic fertilizers. It increases soil aeration, water retention, root growth, microbial matter and also its affordable.

 

Soil forming factors are:

  1.  Rock
  2.  Climate
  3.  Relief
  4.  Biota
  5.  Time

 

 

Rocks:

Soil made up from erosion of soft rocks. It provides soil material, texture, porosity and pH value. Soft rocks means better soil formed than hard rocks.

 

Climate:

Wind, water, glaciers are agents of erosion. Climate determines the type of erosion and its intensity.

 

Relief:

Steep gradient gives underdeveloped soil and plain area gives well developed soil.

 

Biota:

Microbes enrich the soil. Roots from plants help in weathering of rocks and humus content from plants enriches the soil.

 

Time:

Soil formation is a long term process. Time decides maturity of the soil.

 

Transportation in soil:

 

  1. Capillary:
  2.     a) Upward movement of minerals.
  3.     b) Hot and dry climate causes this.
  4.     c) Salts within the soil come to the surface. This results in soil salinity.

 

  1. Leaching:
  2.     a) Downward movement of minerals.
  3.     b) Seen during humid climate.

 

  1.    c) Silica moves downwards but iron and aluminum remain on top. Thus we get laterite soils which are acidic and reddish.

 

  1. Gleying:
  2.     a) In swamps peaty soil is formed.
  3.     b) Excessive potassium is seen.

 

Soil Conservation:

 

Structural solutions for soil conservation:

  1.  Construction of retaining walls. Strengthen slopes of river banks using stone pitching or wire netting.
  2.  On rivers contruction of multi purpose dams. Construction of tri-pods, tetra-pods and groins to prevent erosion.

 

Non structural solutions:

  1. Afforestation.
  2. Discourage cultivation on marginal lands.
  3. Agro forestry.
  4. Along slopes: Contour bunding, terrace farming, basin listing, soil mulching, crop rotation, relay farming, strip farming, organic farming, use of bio fertilizers.
  5. To control wind erosion transverse farming and shelter belts.

 

Fig : Shelter belt

Soil Salinity:

Causes:

  1.   Arid regions are created due to salts on upper layers of the soil.
  2.  Bad drainage due to basin topography and black cotton soil
  3.  Faulty agriculture practices like over irrigation, cultivation of water intensive crops.
  4.  Sea water intrusion into ground water reserves.

Implications:

  1.   Salts of sodium, potassium, manganese come to the top soil.
  2.  Soil fertility is reduced.
  3.  Choice of crops is reduced to only salt resistant varieties like cotton, barley
  4.  Quality of fodder reduced.

 

  1.  Reduced infiltration of water into ground.

Solutions:

  1.  Soil is flushed with water and salts are dissolved and removed but this methods cant be used in india.
  2.  Laying drainage pipes underground to pump out excessive water.
  3.  Lining of canals to avoid seepage.
  4.  Use of agents like gypsum and sodium pyrite to recover soil.
  5.  Discourage use of ground water and encourage rain water harvesting, agro climatic farming.

 

Desertification:

 

  1.  Extreme form of land degradation in semi arid or sub humid areas. Expansion of desert areas.
  2.  It cant be reversed only prevented.

    Solutions:

  1. Constructing retaining walls.
  2. Growing grass on sand dunes.
  3. Cultivation of trees on margins
  4. Transverse farming

 

Types of Soils:



Fig 1: Soil profile of India

  1. Alluvial Soil
  •  Covers 42% of India.                   
  •  Deposited by rivers. Well drained. Most fertile.
  •  
  •  Covers northern plains. Fertility and productivity decreased but productivity increased. These soils are both well drained and poorly drained. In general, they have an immature profile in undulating areas, while in the leveled areas they have a well developed and mature profile. The Khadar type solis are low-lying, frequently inundated by floods during the rainy season. Thus, the khadar occupies the flood plains of the rivers and is enriched by fresh silt deposits every year. The khadar tracts are generally rich in concretions, and nodules of impure calcium carbonate or Kankar. In the drier areas, it also exhibits stretches of saline and alkaline efflorescences. The Bhangar type of soil is above the flood level. It is generally well-drained but contains concretion (kankars] of impure calcium carbonate. The soil texture varies from loamy soil to clayey-loam. It is well drained and rich in humus, phosphoric acid, lime and organic matter. Alluvial soils are, however, deficient in potash.
  1. Red Soil
  •  Covers 25% of country.
  •  Formed due to erosion of granite and gneissic rocks. Best drained soil, least susceptible to water logging. Most vulnerable to soil erosion.
  •  Lacks nitrogen, phosphorous. Supports max crop diversity. Their colour is mainly red because of the presence of ferric oxides. Generally, the top layer is red, while the horizon below is yellowish in colour. The texture of red soils varies from sand to clay and loam. Their other characteristics include porous and friable structure, absence of lime, kankar and carbonates and small quantity of soluble salts. In general, these soils are deficient in lime, phosphate, magnesia, nitrogen, humus, and potash. Intense leaching is a menace to these soils. In the uplands, they are thin, poor, gravelly, sandy, or stony and porous, light-coloured soils, but in the lower plains and valleys, they are rich, deep, dark coloured fertile loams.
  1. Black soil

 

  •  Covers 15% of India.
  •  Formed from erosion of volcanic rock. Lacks nitrogen and phosphorous.
  •  High water retention. Cracks when dry so self ploughing and sticky when wet. In general, these soils have clayey texture and are rich in iron, lime, calcium, potash, aluminium and magnesium. They are, however, deficient in organic matter. When the soil is wet, it becomes difficult to plough the field as the plough gets stuck in mud. It is a matured soil and also known as Regur (cotton soil) soil.
  1. Laterite soil
  •  Found in areas with alternate wet dry season. Used for making bricks. The red colour of the soils is due to the presence of iron-oxide. These soils developed mainly in the highland areas of the plateau. The soils in the higher areas are generally more acidic than those in the low-lying areas. These soils are rich in iron and aluminium, but poor in nitrogen, potash, potassium, lime and organic matter. Although they have low fertility, they respond well to manuring.
  1. Mountainous soil
  •  Immatured soil. Cant support agriculture due to steep slope but can grow grass and shrubs.
  •  Good for lumbering.
  •  Leaves of coniferous trees hard to degrade. Cold climate slows bacterial growth.
  1. Desert soils
  •  Sandy, loose and friable with low water retention capacity. It cant support agriculture.

 

  •  But Indian desert soil is suitable for agriculture under irrigation as its made of aluminum deposits. The desert soils are sandy to gravelly with low organic matter, low nitrogen and varying percentage of calcium carbonate. These soils contain high percentage of soluble salts, but have low moisture content and low water retaining capacity.
  1. Mangrove soils
  •  Bluish green color due to sulphide.
  •  Cant support plants but only mangroves. Present in coastal areas of all states.

 

Karewa Soil

 

    • Karewas are the lacustrine deposits in the Valley of Kashmir. 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 characterised with fossils of mammals and at places by peat.

 

    • 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.



Snowfields

 

    • 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 is immature, generally without soil erosion, It remains frozen and is unsuitable for the cultivation of crops.

 

Soil alkalinity:

    1.  Calcium salts in upper layer causes moderate salinity. But in next stage sodium, potassium salts in upper layer.

  1. This is due to bad drainage and over irrigation.

 

Land use in India:

  1.  India home to 17% of the population but 2.4% of land of the world.

 

                                                           TABLE 1: LAND USE IN INDIA

 

 

Land use

Percentage

Net sown area

46

Forests

23

Land not available for agriculture [cities, development infra]

15

Fallow land

12.5

Pastures

3.5

 

Miscellaneous

  • Desired land use wants to increase forest cover to 33%. Development land should be increase and fallow land reduced.
  • India also has highest percentage of dairy animals but isn’t a leading exporters of dairy products.
  • India’s Net Sown Area [NSA] is 10% of worlds agricultural area but low productivity is seen.
  • India has more natural potential for agriculture than china.
  • India’s NSA is more than china. India’s Gross sown area [GSA] is 199 million hectares. Irrigated land = 61 million hectares.
  • Cropping intensity = G.S.A / N.S.A = 140% target = 160%

Chapter Review

Score more than 80% marks and move ahead else stay back and read again!

 

Q1:Macronutrients are

nitrogen, phosphorous

potassium, calcium

magnesium, sulphur

all



Q2: Micronutrients are

Boron, chlorine

iron, magnesium

iron, copper.

all

 

Q3: Ideal ratio of N:P:K should be

8-4-1

1-2-3

4-2-1

1-2-4



Q4:Excess use of fertilizers may lead to

chemicals harden the soil and make it infertile

Nitrate poisoning in ground water leads to stomach cancer

Eutrophication of lakes.

all

 

Q5:Unmatured soil is also

red

black cotton

alluvial

mountainous