Lecture 5a Soil Taxonomy

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Lecture 5aSoil Taxonomy

• Purpose of Soil Taxonomy
• 1. Organize knowledge about soils
• 2. Understand relationships among different soils
• 3. Establish groups or classes for practical
  purposes.
• a. predicting behavior
• b. identifying best uses
• c. estimating productivity
• d. extending research results

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Soil Taxonomy

• Soils are classified into into six categories
  based on diagnostic characteristics
• The last category will place the soils into one
  of the 12 Soil Orders.

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Soil Taxonomy
Fine-loamy mixed, superactive, mesic Aquic
Argiudolls
(This is the name of a specific soil in Soil
Taxonomy)

• Orders (12)
• Suborders (54)
• Great Groups (211)
• Subgroups (1,100)
• Family (7,000)
• Series (a lot!)

This is the name of one Of the 12 large categories
Mollisol - oll
Oder - root of order
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Orders
Fine-loamy mixed, superactive, mesic Aquic
Argiudolls

• Highest and most general of the soil
  classification system (similar to the phylum in
  plant taxonomy)
• Based on conditions under which the soil developed

Order oll Mollisols
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Suborders
Fine-loamy mixed, superactive, mesic Aquic
Argiudolls

• Grouped by similarities in soil formation such as
  wetter/dryer soil, colder/warmer soil, etc.

Ud Udic Moisture
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Great Groups
Fine-loamy mixed, superactive, mesic Aquic
Argiudolls
Sub Order
Order
Great Group

• Based on differences between soil horizons

Argi Clay accumulation
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Sub Groups
Fine-loamy mixed, superactive, mesic Aquic
Argiudolls
Sub Order
Sub Group

• Describes a profile characteristic, wetness,
  sand, tonguing of E, etc.

Order
Great Group
Aquic wet soil
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Family
Fine-loamy, mixed, superactive, mesic Aquic
Argiudolls
Sub Order
Sub Group
Family
Order
Texture, clay minerals, CEC, temp,
Great Group

• Based on soil properties that affect management
  and root penetration, such as texture,
  temperature, and depth

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Series Le Sueur
Fine-loamy mixed, superactive, mesic Aquic
Argiudolls
Sub Order
Sub Group
Family
Order
Great Group

• Named from the town or landscape feature near
  where the soil was first recognized (Lester
  Lester Prairie, MN. Other examples Clarion,
  Nashwauk, Milaca, Port Byron, Zimmerman. Le Sueur
  for Le Sueur County, MN.)

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Diagnostics Horizons- Used to place soils into
one of the 12 Soil Orders

• Surface (Epipedon)
• Mollic
• Umbric
• Histic
• Ochric

• Subsurface
• Argillic
• Natric
• Spodic
• Oxic
• Cambic
• None

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Soil Taxonomy- Diagnostic Surface Epipedons

• Mollic Epipedon - thick, dark, soft, surface
  layer.
• Characteristics
• Thick - greater than 10 inches High base
  saturationgt 50
• Mineral soil
• Soils formed under prairie vegetation

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Other Epipedons

• Umbric - like mollic, but low base saturation
• Histic - Organic Soil - saturated with water, gt
  - organic matter
• Ochric - thin, light colored - surface layers
  that do not fit any of the above

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Comparison of Epipedons
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Diagnostic Subsurface Horizons

• Argillic - illuvial horizon of clay accumulation
  - Bt
• Natric - same as argillic but with gt 15
  exchangeable sodium (Na) - Btn

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Diagnostic Subsurface Horizons

• Spodic - illuvial accumulation of oxides of Al
  and Fe (sesquioxides) and OM, red or dark red
  color - only found in acid sandy soils, with high
  rainfall- generally found below E horizon.
  Contains a Bhs or Bs horizon

Oi E Bhs Bs C
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subsurface horizons (cont.)

• Oxic - very weathered layer of only Fe and Al
  oxides and 11 clay minerals, low pH and not very
  fertile (found in tropical soils) Bo
• Cambic - slightly altered layer - not weathered
  enough to be argillic, Bw horizon designation or
  development of color and or structure
• NONE - no diagnostic subsurface horizon present

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Comparison of Subsurface Diagnostic Horizons
Spodic
Cambic
less developed
more Al and Fe
Argillic
very weathered
more sodium
Oxic
Natric
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12 Soil Orders - Each Order has a diagnostic
epipedon and subsurface horizons which could be
none. WEB SITE for soil orders
www.mines.uidaho.edu/pses/teach_res

• Entisol
• Inceptisol
• Andisols
• Spodosols
• Mollisols
• Alfisols

• Ultisols
• Oxisols
• Aridisols
• Vertisols
• Histosols
• Gelisols

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Entisol - ent

• Recent soils - minimal
  development, little
  horizonation, young
  soils.
  
• 12.5 of world,
  Ochric none

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Entisol - Idaho
A R
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Vertisol - ert

• Inverted - soils with
  high clay content, large
  shrink swell potential
  - gradually invert on
  themselves,
• 2.1 of the world,
  Mollic or Ochric none

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Vertisol Bss at slickenslide
soil cracks
Slickenslide
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Inceptisol - ept

• Inception - soil shows the beginning of horizon
  development, little or no illuviation,
• 15.8 of world, Ochric or Umbric cambic.

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Inceptisol

• Soil Formed in colluvial material in mountains
  of Idaho.

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Aridisols - id

• Arid regions of the
  world (19), lt 10 in.
  of rainfall, usually
  contain carbonates,
  
• Ochric cambic or
  argillic or other
  diagnostic feature.

A Bw Bk C
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Aridisol in Idaho
A Bt Bk Bkqm R
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Aridisol - Nevada

• NaCl Salt
  
  accumulates on
  the surface and
  in the
  subsurface.

Az Bz C1 C2
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Mollisols - oll

• soils with thick, dark,
  soft surface - mollic cambic,
  natric, argillic or none -
  high base
  saturation - soils of the prairie
  
• 9 of the world

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Mollisol

• This mollisol formed in a new parent material
  (loess) that buried the original soil -the Btb (b
  buried).
• Mollisol from Kansas that is developed in
  Limestone bedrock.

A1 A2 Bw BC R
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Spodosols- od

• acid sandy soils with
  thick E and red Bhs -
  ochric and spodic -
• 5.4 of the world -
  infertile soils.

Oi E Bhs Bs C
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Alfisol -- alf

• fertile forested soils with ochric and
  argillic - high base
  saturation (gt 35) -
  forested soils
• 7 of the world.

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Ultisols - ult

• soils more weathered
  than Alfisols - ochric
  and argillic - low base
  saturation lt 35 - redder and
  more acid than Alfisols
• 8.5 of the world - less
  fertile than Alfisols

A E Bt1 Bt2 BC
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Alfisol Ultisol
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Histosols - ist

• peat soils - organic
  material - histic
• 0.8 of the world
• Histic Epipedon.

Oe1 Oe2 Oe3 Oe4 Oa 2C
Photo USDA
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Dyad

• Describe the Soil Order that is most likely found
  in your home town.

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Andisols - and

• soils from volcanic ash
  - very light - low bulk
  density -- 1 or the world

A Bw 2BC 2C
A Bw Ab Bwb Ab
Andisol from Idaho
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Oxisols - ox

• Soils with Oxic horizon - very weathered - soils
  of the tropics. low pH - acid soils - high in
  11 clay minerals
• 9.2 of world

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Oxisol
Ap1 Ap2 Bo1 Bo2 Bo3
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Oxisol Puerto Rico
Ap A Bo1 Bo2 BC C
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Gelisol - el

• New Order as of 1998 - soils with permafrost
  (formerly Cryochrepts - or frozen Inceptisols)
• Cf - horizon

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Soil Orders USA
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Soil Orders in Minnesota
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Soil Orders Wisconsin Northern Illinois
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Soil Suborders of Minnesota

• Mollisol - Udoll - Boroll - Aquoll - Ustoll
• Alfisol - Udalf - Boralf - Aqualf
• Dropped in 1998
• Entisol - Orthent - Psamment Aquent -
  Fluvent
• Inceptisol - Udept - Aquept
• Spodosol - Orthod
• Vertisol - Aquert
• Histosol - Fibrist - Hemist - Saprist

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Suborder definitions

• Ud - Udic moisture moist -southern Mn type
  climate Us Ustic Dry
• Bor - Boreas northern Mn. Climate (Frigid
  Temperature regime)
• Aqu - Aquic moisture saturated soil - high
  water table - Gleyed conditions
• Orth - true or simple - regular Entisols
  Spodosols
• Psamm - sand - sandy Entisols
• Fluv - floodplain irregular Organic matter

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Udoll - Ustoll - Aquoll
Ustoll
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Udalf - Boralf - Aqualf
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Orthent - Psamment Aquent - Fluvent
Orthent
A Bw C
Not Cambic due to being too sandy
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• Fluvent Soils of the floodplains.
• Lots of layers that are deposited when the river
  floods

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Orthod
Minnesota Orthod
Wisconsin Orthod
A E Bhs Bs C
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Udept - Aquept
EUTRUDEPTS
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Aquert
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Fibrist - Hemist - Saprist
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Suborder Map
You need to know the location of the suborders in
Minnesota
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What is the soil order here? --gt
Entisol
The End