MAJOR TYPES OF SOIL

SOIL TYPES AND THEIR MICROFLORA

·       Soil types are classified according to many more factors.

·       Soils are classified on the basis of Colour, Depth, pH, Geology (Study of Earth science), Productivity, Texture and Process of formation (Weathering).

Soil types according to Depth

·       Soil types according to depth are as follows:

a)    Shallow soil - Soil depth less than 22.5 cm. Only shallow rooted crops are grown in such soil (e.g.) Paddy.

b)    Medium deep soil - Soil depth is 22.5 to 45 cm. Crops with medium deep roots are grown in this type of soil (e.g.) Sugar cane, Banana, Blackgram and Greengram.

c)     Deep soil - Soil depth is more than 45cm. Crops with long and deep roots are grown in this type a soil (e.g.) Mango and Coconut.

Soil types according to Geology

·       Geologically, Indian soils can broadly be divided into soils of peninsular India and soils of extra-peninsular India.

a)  Soils of Peninsular India or Sedentary soils - The soils of Peninsular India are formed by the decomposition of rocks in situ, i.e. directly from the underlying rocks. Soils of Peninsular India are transported and re-deposited to a limited extent and are known as Sedentary soils.

b)    Soils of the Extra-Peninsula India or Transported soils or Azonal soils - The soils of the Extra-Peninsula India are formed due to the depositional work of rivers and wind. They are very deep. They are often referred to as Transported soils or Azonal soils.

Major Soil types in India

1)    Alluvial soils

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

·       Also called as “Riverine soil” because it is mainly found in the River basin.

·       Colour – Light Grey to Ash Grey

·       Texture – Sandy to Slit loam or Clay

·       Soil formation - Silt brought by rivers

·   Soil composition - Rich in Lime and Potash; Poor in Phosphorous, Humus and Nitrogen.

·       Soil characteristics

ü  Highly fertile

ü  Fine grained both in New alluvium (Khadar) and Old alluvium (Bhangar).

·      Prevalence in Indian states - Punjab, Haryana, Uttar Pradesh, Madhya Pradesh, Bihar and West Bengal.

·       Crops grown - Rice, Wheat, Sugarcane, Cotton, Oil seeds and Jute.

·  Soil microorganisms – Bacteria (Bacillus sp. and Pseudomonas sp.) and Fungi (Aspergillus sp., Penicillium sp. and Mucor sp.).  

2)    Black soil

·       Also called as “Black cotton soil” or “Indian Regur soil”. Regur means Cotton and this soil is best soil for Cotton cultivation.

·       Colour – Deep Black to Light Black

·       Texture – Clay and Slity loam.

·       Soil formation - Weathering of Volcanic rocks

·    Soil composition - Rich in Lime, Aluminium, Calcium, Potash, Iron and Magnesium; Poor in Nitrogen, Phosphoric acid, Organic matter and Humus.

·       Soil characteristics

ü  Mature soil.

ü  Black soil retains water, making them ideal for crops that require water year round.

ü  Soil pH is alkaline

ü  Sticky in nature

·     Prevalence in Indian states - Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh and Tamil Nadu.

·       Crops grown – Cotton, Sugarcane, Sorghum, Wheat, Rice, Oilseeds and Tobacco.

·  Soil microorganisms – Iron oxiders & reducers (Thiobacillus ferrooxidans and Metallogenium sp.), Organic iron accumulators (Bacillus sp., Pseudomonas sp., Serratia sp., Klebsiella sp., Acinetobacter sp., Corynebacterium sp., Streptomyces sp. and Nocardia sp.) and Aerobic iron reducers (Bacillus sp. and Pseudomonas sp.). 

3)    Red soil

·       Seen mainly in Low rainfall area.

·       Also called as “Omnibus group”.

·       Colour – Red because of Ferric oxide. The lower layer is Reddish yellow or Yellow.

·       Texture – Sandy to Clay.

·       Soil formation - Decomposition of Granite and Metamorphic rocks (formed through the transformation of pre-existing rocks in a process known as Metamorphism i.e. “change in form”).

·       Soil composition - Rich in Iron; Poor in Lime, Phosphorous, Calcium and Nitrogen.

·       Soil characteristics

ü  Porous, friable structure.

ü  Not water retentive.

ü  Red soil actually has a very low level of Humus and require fertilizers when used for farming.

ü  Soil pH is Acidic in nature.

·       Prevalence in Indian states - Tamil Nadu, Kerala, Karnataka, Madhya Pradesh, Orissa and Chattisgarh.

·   Crops grown – Wheat, Rice, Cotton, Sugarcane, Oilseeds, Tobacco, Maize, Pulses, Potatoes and Fruits.

·       Soil microorganisms – Bacteria, Actinobacteria and Fungi. 

4)    Laterite soil

·       Observed in the areas of high temperature and high rainfall.

·       Also called as “Later soil” which means Brick.

·       Colour – Red because of Iron oxide.

·       Texture – Soft when wet and Hard when dried.

·       Soil formation - Leaching of Laterite rocks

·       Soil composition - Rich in Iron; Poor in Lime, Phosphorous, Calcium and Nitrogen.

·       Soil characteristics

ü  Agriculturally less important.

ü  Bricks are made for house construction.

ü  Non-sticky in nature.

·      Prevalence in Indian states - Karnataka, Kerala, Tamilnadu, Andhra Pradesh, Madhya Pradesh, West Bengal, Odisha, Assam and Orissa hills.

·       Crops grown – Rice, Ragi, Sugarcane, Coconut, Cashew, Tea, Coffee and Rubber.

·  Soil microorganisms – Iron oxiders & reducers (Thiobacillus ferrooxidans and Metallogenium sp.). 

5)    Forest and Hill soil

·       Observed in the areas of high rainfall.

·       Colour – Dark Brown.

·       Texture – Slity loam.

·       Soil formation - Decomposition of Organic matter.

·       Soil composition - Rich in Humus; Poor in Potash, Phosphorous and Lime.

·       Soil characteristics

ü  Characters changes with parent rocks and climate.

ü  Soils are enriched by fallen leaves and rich in Organic matter and Total nitrogen.

ü  Require good deal of fertilizers.

·   Prevalence in Indian states - Himalayan region, Karnataka, Kerala, Tamil Nadu, Western Ghats and Eastern Ghats.

·       Crops grown – Temperate fruits, Spices, Tea and Coffee.

·       Soil microorganisms – Nitrifiers, Denitrifiers and Ammonifiers.

6)    Desert soil

·       Observed under Arid (Lack of water) and Semi-Arid conditions.

·       Desert soils occur in the Low rainfall track.

·       Also called as “Arid soil”.

·       Colour – Red to Brown

·       Texture - Sandy soils.

·      Soil composition - Rich in Soluble salt contents; Poor in Nitrogen and Organic matter and have a high pH value.

·       Soil characteristics

ü  Impure Calcium carbonate content is high which restricts the infiltration of water.

ü  Desert soils are often subjected to Wind erosion.

·    Prevalence in Indian states – Western Rajasthan, North Gujarat and Southern Punjab.

·  Crops grown – Only drought resistant and salt tolerant crops such as Barley, Cotton, Pearl millets, Maize and Pulses.

·     Soil microorganisms – Chemolithotrophs (Pseudomonas sp.). 

7)    Saline and Alkali soil

·       Also called as “Usara soil”

·       Soil formation - Accumulation of Soluble salt.

·   Soil composition - Rich in Chloride, Calcium, Sodium, Potassium and Magnesium; Poor in Nitrogen and Calcium.

·       Soil characteristics

ü  Infertile soil.

ü  Gypsum is added to improve the soil.

·     Prevalence in Indian states - Bihar, Uttar Pradesh, Haryana, Punjab, Rajasthan and Maharashtra.

·    Crops grown – Barseem (Trifolium alexandrinum – Fodder for Cattles), Dhaincha (Sesbania grandifola - Agathi) and Leguminous crops (Alfalfa, Clover, Peas, Beans, Lentils, Lupins, Mesquite, Carob, Soy and Peanuts).

·       Soil microorganisms – Halophilic microorganisms.

 

8)    Peaty soil

·       Seen in regions with High rainfall and Average temperatures

·       Also called as “Marshy soil”.

·       Colour – Black

·       Texture – Loamy texture (Combination of Sand, Slit and Clay sized particles)

·       Soil composition – Rich in Organic matter and Humus.

·       Soil characteristics

ü  Highly acidic soil.

ü  Suitable for agriculture, but these soils need proper care so they do not leach away all their nutrients in the heavy rainfall.

·       Prevalence in Indian states – Bihar, Uttaranchal, Tamil Nadu, Kerala, Coastal track of Orissa, Sunderban area of West Bengal.

·      Crops grown – When properly drained and fertilized, these soils produce good crops of Rice.

·       Soil microorganisms – Anaerobic microorganisms are present in high number.