11. Soil orders.pptx ........soil resource inventory

Soil Order
Characteristics & Distribution
Lecture: 11
1
11 April 2024
SAC 201 Soil Resource Inventory (1+1)

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USDA Soil Taxonomy
Order
12 orders
Name of order Formative element
Entisol ent
Inceptisol ept
Alfisol alf
Ultisol ult
Oxisol ox
Vertisol ert
Mollisol oll
Aridisol id
Spodosol od
Histosol ist
Andisol and
Gelisol el
USA VIA HOME AG
MAAGAVI HOUSE
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AVAGAMI HOUSE

3
Entisols (Soils of initial origin / immature )
 Very recently developed mineral soils with no
diagnostic horizon (other than ochric or anthropic epipedon)
 Slight degree of soil formation (either limiting
time or exceeding unfavorable condition )
 Parent material:
 Resistant to weathering (parent material quartz)
 Not altered much by soil forming process
Characteristics
Distribution
 Associated with steep slopes, flood plains, coastal lands and sand dune areas
 World: Sahara (Africa), Asia, Australia, middle-east countries, South America, USA,
South Africa and Russia (Constitute 18% of soils worldwide)
 India: Flood plains, sand dunes, rocky humid regions and coastal land forms distributed
in all the states

4
Entisols (Soils of initial origin / immature )
 Susceptible to erosion
 Poor physical condition
 Lesser depth in case of eroded soils
 Psamments: Lesser clay content, Low water holding
capacity, low nutrient status
Constraints
Utility
1. Recent alluvium: Productive & suitable for agriculture
2. Barren sands & eroded soils: Infertile; grazing & forestry use
3. Sand dune areas: Raising single crop by conserved moisture
Classification
1. Aquents 2. Arrents (fragments of diagnostic horizon) 3. Psamments
4. Fluvents (recent flood plains) 5. Orthents (Non-fluviatile)

5
Inceptisols – Recently developed soil
 Early stage of soil formation (beyond Entisols but < Alfisols)
 Poor soil profile development
 Presence of diagnostic horizons viz., cambic, umbric or mollic
 Limited leaching
 Less accumulation of material in subsoil
 Soils developed owing to the alteration of parent material to
develop soil structure
Characteristics
Distribution
 Throughout the world are commonly found forming in
alluvium on floodplains and delta deposits.
 Varied climatic conditions: Semi-arid to humid)
 All vegetation conditions: Grassland to tundra forest
 They constitute 15% of soils worldwide

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Inceptisols– Recently developed soil
1. Aquepts
2. Udepts
3. Ustepts
4. Xerepts
5. Cryepts
6. Anthrepts: Plaggen/anthropic epipedon
Classification
Utility
1. Many Inceptisols agriculturally very productive and provide excellent natural grazing
 In past most of this soils were Brown Forest, Andisol and Soil Brun Acide

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Alfisols
 Light coloured surface horizon (Ochric epipedon)
 Presence of Argillic sub horizon (accumulation of clays)
 Base saturation : > 35%
 Surface horizon: Grey to brown
 Strongly weathered soils than Inceptisol but less weathered
than Ultisol
 Having a favorable moisture balance and good fertility,
they are very productive soils for agriculture.
Characteristics
Distribution
 Sub-humid and humid regions
 World: USA, South America, Northern Europe, Africa, Brazil,
southeast Asia, eastern Australia and Russia (constitute 10%
of soils worldwide)
 In India, Red soils (Rhod-, Pale-, Hapl- ustalfs) predominantly
observed in TN, AP, Karnataka, MH, Orissa, MP, Assam,
Arunachal Pradesh, Bihar and HP

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Alfisols
 Productive and suitable for agriculture
 In India, these soils growing crops like, wheat, maize,
sorghum, rice, and horticultural crops (mango. Cashew,
jackfriuts and litchi)
Utility
Classification
1. Aqualfs
2. Ustalfs
3. Udalfs
4. Xeralfs
5. Cryalfs
 In past most of this soils were
Gray Brown Podzols, Planosols
and some half Bog soils

9
Aridisols (Soils of arid region)
 Soils remain dry for most part of the year
 A negative moisture balance in these soils inhibits eluviation [Salts
accumulation: Surface and/or in solum]
 Presence of calcic, gypsic or salic horizons [Calcification and salinization are
important soil forming processes acting in these soils]
 Presence of ochric epipedon
 They are light in color - little vegetation to add organic matter to the soil profile
 Soil horizons are weakly developed and Na ion is often high in concentration
Characteristics
Distribution
 Mineral soils of dry places [arid and semiarid] where moisture is scarce; high ground
water table
 World: Africa, Australia, South America, USA, South Asia and Russia
 India: Rajasthan, Punjab & Haryana (non-gypsiferous) and Gujarat
(constitute 12% of soils worldwide)

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Aridisols (Soils of arid region)
 Limited soil moisture (Aridic climate) or Xerophytic climatic
conditions and brackish water comes to surface
 Higher salt content
Constraints
Utility
1. Productive if water is available with reclamation
2. Suitable for grazing and tree crops tolerant to salinity
Classification
1. Cryids
2. Salids
3. Durids
4. Gypsids
5. Argids
6. Calcids
7. Cambids: common type
of Aridisols

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Ultisols - similar to Alfisols except low base saturation
 More weathered soils than Alfisols
 Presence of argillic or kandic horizon
 More acidic than Alfisols but not as acidic as Spodosols
 Highly weathered soils, they are often red / yellow in color
reflecting the oxidation of iron and aluminum.
 Accumulation of clay at subsoil which distinguishes
them from Oxisols which do not.
Characteristics
Distribution
 Warm, humid and subtropical regions
 High rainfall and forested vegetation
 Mid to low altitudes regions
 World: USA, South America, south-east Asia and central Africa
 India: Kerala, Tamil Nadu, Orissa and north eastern states

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Ultisols - similar to Alfisols except low base saturation
1) Aquults 2) Udults 3) Ustults 4) Xerults 5) Humults: high OC (12 kg/m2) within 1m soil
Classification
Utility
1. Suitable for agriculture after liming and fertilization
2. Suitable for pineapple, sugarcane, coffee, cocoa, coconut and rubber
3. Suitable for natural vegetation
 Fertility: Low
 Base saturation: low (<35%)
Constraints

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Oxisols (Strongly weathered mineral soils of Tropics)
 Surface: Oxic horizon
 High Fe & Al oxides
 Silica leached out
 Low in weatherable minerals, bases and exchange capacity
 Low water and nutrient holding capacity
 Clay content: High but non sticky (1:1 type; Kaolinite)
 Poor in fertility
 Low cation exchange capacity
Characteristics
Distribution
 Found in warm, rainy climates under broadleaf, evergreen
vegetation
 World: Central Africa, South America and South-east Asia
 India: In tropical India Not yet reported

14
Oxisols (Strongly weathered mineral soils of Tropics)
1. Aquox 2) Torrox 3) Ustox 4) Udox 5) Perox
Classification
Utility
1. Grazing, forestry
2. Plantation crops: Coffee, rubber, cocoa, sugarcane
3. Tropical fruit crops: Pineapple, coconut, cashew nuts,
jackfruit
1. Shifting agriculture (>20 years) common practice adopted in such areas
 Low in fertility
 Phosphate fixation (High Fe and Al)
 Liable to crusting (hard surface layer)
 Chemically-degraded soils
Constraints

15
Mollisols (dark coloured, organic, grassland soils)
 Mollisols are among the most fertile soils (best agricultural soils) on the Earth
 Thick and organic matter rich (Mollic epipedon)
 Well-structured (granular or crumb) top soil; soft consistency when dry.
 Soil colour: Dark brown to black organic rich surface layers.
 High WHC; High base saturation with abundant calcium
 Subsurface horizons either rich in illuviated clay (Argillic) or
 calcareous (Calcic) or gypsiferous (Gyspic) nature
Characteristics
Distribution
 Grassland soils of Sub-humid (semiarid) to humid environment
 World: USA, South America and Russia
 India: Tarai region of UP, Uttarkhand, HP, Bihar, MH and MP

16
Mollisols (dark coloured, organic, grassland soils)
1. Aquolls
2. Albolls: Albic (bleached) horizon over an argillic or natric
horizon and which has chroma 2 or less
3. Udolls
4. Ustolls
5. Xerolls
6. Cryolls
7. Rendolls: 40% or more of CaCO3 content either within or
below mollic epipedon
Classification
Utility
1. Suitable for farming (wheat, maize, sorghum)
2. In drier regions used for grazing

17
Vertisols - Clay rich, dark coloured soils
 Clay content: > 30 %
 Swells on wetting & Shrinks on drying
 Colour: Black or dark
 Sticky and plastic in consistency
 Surface deep cracks under dried condition
 Sub surface horizon
 Gilgai micro-relief or slickensides
Characteristics
Distribution
 Parent materials containing basaltic composition
 Sub-humid to semi-arid climates (RF: 500 to 1500 mm/year)
with pronounced dry season
 World: Africa, Australia, and USA
 India: Maharashtra, TN, AP, MP and Rajasthan
(constitute 2 % of soils worldwide)

18
Vertisols - Clay rich, dark coloured soils
1) Xererts 2) Torrerts 3) Uderts
4) Usterts 5) Aquerts 6) Cryerts
Classification
Utility
1. Very productive if managed
2. Suitable for agriculture with management measures
3. Suitable for dryland and rainfed farming
1. Swell shrink properties
2. High clay content
3. Poor infiltration rate or hydraulic conductivity
4. Susceptible to water erosion
Constraints

19
Histosols (Soils rich in organic matter)
 Originated from organic materials (peat, muck, bog soils)
with thick peaty horizon (Histic epipedon)
 Organic matter is 12 - 30 %
 The minimum amount of OM required is 20%, if no
clay content
 Thumb rule, a soil without permafrost and have half or more
of upper 80 cm is organic matter
 High quantities of plant and animal residues in various
stages of decomposition (lower in swamps than herbaceous)
 Moderate accumulation of iron and aluminium sulphates,
iron pyrite (tidal swamp areas)
 Rate of accumulation of peat is 0.5 to 1 mm per year
 They are often "mined" for peat which is dried and burned
as fuel.
Characteristics

20
Histosols (Soils rich in organic matter)
 Need for drainage: reducing anaerobic condition
 Sulphate accumulated soils: No drainage (formation of H2SO4)
 Toxicity of Fe and Al and Deficiency of phosphorus
Constraints
Utility
1. Hemists and Fibrists: Suitable for natural vegetation (growing vegetables)
2. Folist: Suitable for farming
Classification
1. Folists: free drained areas 2. Fibrists: depression areas 3. Hemists: Moderately
decomposed OM 4. Saprists: Highly decomposed
Distribution
 Water saturated environment
 Temperate regions (slow decomposition)
 World: Europe, USA, Canada and north-west Asia
 India: pockets of Kerala, Tripura and Andaman & Nicobar islands

21
Spodosols - Strongly weathered mineral soils
 Surface horizon: Bleached, wood ash coloured, mineral soil
 Subsurface: Accumulation of humus (Bh) and sesquioxides (Bs)
 Surface litter composed of pine needles breaks down
in the presence of water to form a weak organic acid.
 Coarse textured siliceous parent material favours free leaching
conditions
Characteristics
Distribution
 Under coniferous vegetation
 Cool, humid climate conditions
 World: Europe, Canada and USA
 India: Not reported

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Spodosols - Strongly weathered mineral soils
1. Aquods 2. Orthods 3. Cryods 4. Humods: High OC (> 6%) within spodic horizon
Classification
Utility
1. Grazing, forestry
2. Agriculture: Need management and fertilization
 Fertility: Low
Constraints
Podzol, Brown podzolic and Hydromorphic soils (Groundwater podzols)

23
Andisol (Soils of volcanic origin)
 Colour : Dark
 Bulk density : < 0.9 Mg m-3
 Don’t have albic horizon but have andic properties
 Parent material: 60% Volcanic ash with in 60 cm depth
 Mineral composition: High allophane
 Porosity: High and Surface area: High
 Water holding capacity: High
 Very fertile
 Fixes Phosphorous
Characteristics
Distribution
 World: Japan, Indonesia, New Zealand, Phillipines, Rift valley of Africa, west coast of
USA and south America
 volcanic islands and mountains of "The Ring of Fire", that encircles the Pacific Ocean
from North America through Japan
 India: Andaman and Nicobar

24
Andisol (Soils of volcanic origin)
Utility
Productive, suitable for less P demanding crops/agriculture eg. Sweet Potato
 P fixation is the main constraint
 Civil construction: Not suitable
 Liable for wind erosion
 Management : Low bulk density, poor compactability, fluffiness
Constraints
Classification
1. Aquands
2. Cryands
3. Torrands
4. Udands
5. Ustands
6. Xerands
7. Vitrands: Andisols that
have a duripan or petro
calcic (60% vitric
volcanic ash)

25
Gelisol (Soils of permafrost regions)
 Contains gelic materials
 Presence of permafrost within 2m depth
 Cryoturbation (Frost churning): predominant
 Soil forming process is limited (may or may not
present diagnostic horizon)
 Freezing and thawing: Major factor
 No downward movement of soil solution
Characteristics
Distribution
 Tundra region (Northern and southern hemisphere)
 World: Northern USA, Canada, Green land, Russia,
Mangolia and Russia.
 India: not yet reported (higher Himalayas)

26
Gelisol (Soils of permafrost regions)
 Very low soil temperature
 Low organic matter
 Poor soil development
Constraints
Utility
1. Not cultivable (cold climate)
2. Suitable for natural vegetation
Classification
1. Histels: Organic soil materials or saturated with water for 30 or more days in a year
2. Turbels: Shows cryoturbation in the form of irregular, broken or distorted horizon
boundaries
3. Orthels
Cryoturbation

11. Soil orders.pptx ........soil resource inventory

Salient characteristics of soil orders
Based on Diagnostic property Order
Nature of soil material Very high content of organic matter Histosols
Cracking or swell-shrink clay Vertisols
Andic material > 35 cm soil Andisols
Dark organic surface layer underlain by permafrost Gelisols
Presence or absence of
diagnostic horizons
Spodic horizon Spodosol
Oxic horizon Oxisols
Argillic horizon but High base status Alfisols
Argillic horizon but with low base saturation Ultisols
Mollic epipedon and high base saturation Mollisols
Cambic horizon (or) umbric, plaggen epipedon Inceptisols
No distinct horizons Entisols
Soil moisture regimes Aridic or dry or saline Aridisols
29

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Order Typical Character
Alfisol Argilic subsoil horizon, BS >35 % (red soil), suitable to agriculture
Andisol
Volcanic soils, BD: < 1 Mg m-3; Fixes phosphorous, more porous, WHC – high, Suitable for
less P demanding crops
Aridisol
Dry soil conditions, accumulation of salt, calcic, gypsic or salic horizons, organic matter –
Low, Productive if water available
Entisol
Soil formation - initial stage; No profile development, PM – Not altered; poor physical
conditions; alluvial soil – Fertile, sand dunes – infertile
Histosol Rich OM (12-30 %), Dark colour, peat, muck soils, suitable for farming and natural vegetation
Gelisol Permafrost layers, cryoturbation, freezing and thawing, low OM; Suitable for natural farming
Inceptisol
Recently developed soil; soil formation – early stage, poor profile development, cambic,
umbric, mollic horizons, suitable for farming
Mollisol Grass land soils; dark, high OM, structured, WHC – High, BS – High, suitable for farming
Oxisol
Strongly weathered, High Fe &Al, Low fertility, High 1:1 clay, low CEC, fixation of P, Suitable
for natural farming, tree crops
Spodosol
Strongly weathered mineral soil, Surface: humus accumulation and Fe&Al oxides
Accumulation, fertility – Low, suitable for grazing, forestry
Ultisol
Similar to Alfisol; BS: < 35%; Argilic, kandic horizon, acidic, Fertility – Low; Suitable to
agriculture after amendments
Vertisol
Clay > 30 %; dark, presence of surface cracks in summer, shrink and swell properties, slicken
sides at subsurface, suitable for dry land and rainfed farming
Ease
Recall

11. Soil orders.pptx ........soil resource inventory

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11. Soil orders.pptx ........soil resource inventory