Soil TaxonomyProperties of Soil
Plant & Soil Science
Property #1: Soil has Horizons (layers)
Property #2: Soil has Color…
Property #3: pH Levels
Soil Property #4 - Organic Content
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Desert soils have low
organic content.
Grasslands have high
organic content.
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The exact type of
vegetation is also
important because it
also affects pH.
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Pine needles add acid
to the soil.
Grasses conserve
calcium and
magnesium (bases).
Most crops like a
neutral pH.
Order
Soil Taxonomy- 12 Soil Orders
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Soils are
classified into
into six
categories based
on diagnostic
characteristics
The last (largest)
category will
place the soils
into one of the
12 Soil Orders.
Soil Taxonomy
Fine-loamy mixed, superactive, mesic Aquic Argiudolls
(This is the name of a specific soil in Soil Taxonomy)
1)
2)
3)
4)
5)
6)
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
Orders
Fine-loamy mixed, superactive, mesic Aquic Argiudolls
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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
Suborders
Fine-loamy mixed, superactive, mesic Aquic Argiudolls
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Grouped by similarities in
soil formation such as
wetter/dryer soil,
colder/warmer soil, etc.
Sub
Order
Order
Ud = Udic Moisture
Great Groups (not required to know)
Fine-loamy mixed, superactive, mesic Aquic Argiudolls
Sub
Order
Great
Group
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Based on differences
between soil horizons
Order
Argi = Clay
accumulation
Sub Groups (not required to know)
Fine-loamy mixed, superactive, mesic Aquic Argiudolls
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Describes a profile
characteristic, wetness,
sand, etc.
Sub
Group
Sub
Order
Great Order
Group
Aquic = wet soil
Family (not required to know)
Fine-loamy, mixed, superactive, mesic Aquic Argiudolls
Family
Texture, clay minerals, CEC, temp,

Based on soil properties that
affect management and root
penetration, such as texture,
temperature, and depth
Sub
Group
Sub
Order
Great
Group
Order
Series (not required to know)
Fine-loamy mixed, superactive, mesic Aquic Argiudolls
Family
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Named from the town or landscape
feature near where the soil was
first recognized (Eleva= Eleva, WI
or Gale for Galesville, WI .)
Sub
Group
Sub
Order
Great
Group
Order
Soil Orders – Upper Midwest
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
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Entisol
Inceptisol
Andisols
Spodosols
Mollisols
Alfisols
Ultisols
Oxisols
Aridisols
Vertisols
Histosols
Gelisols
The 12 Soil
Orders
Orders with unique parent materials:
Andisols (and)
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Volcanic ash soils.
Histosols (ist)
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Organic soils.
Vertisols (ert)
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High shrink/swell
clay soils.
Orders formed in unique
environments.
Aridisols (id)
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Arid climates.
CaCO3 accumulation
in subsoil.
Gelisols (el)
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Colder climates.
Permafrost layer
within 2 m of
surface.
Oxisols (ox)
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Tropics and
subtropics.
Intensely weathered.
Orders by age.
Entisols (ent)
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‘Baby’ soil.
Little to no
morphological
development.
Inceptisols (ept)
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‘Toddler’ soils.
Weakly developed
sub-surface
horizons.
Ultisols (ult)
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Older soils.
“Ultimately
weathered”.
Strongly leached.
Sub-surface clay
accumulation.
< 35% base sat. in
sub-soil.
Orders developed under unique
vegetative ecosystems.
Alfisols (alf)
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Forest soils.
Usually an A-E-B
type horizon
development.
The A horizon is
usually less than 25
cm.
Mollisols (oll)
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Grasslands soil.
Thick, dark A
horizon.
High % base
saturation.
Spodosols (od)
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Acid forest soils.
Usually sandy.
Thick, bright white E
horizon.
Sub-surface layer of
accumulated metalhumus complex
(Bhs and Bs
horizons).
Summary:
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3 orders with unique parent materials
(Andisols, Histisols, Vertisols).
3 orders with unique environments
(Aridisols, Gelisols, Oxisols).
3 orders by age of development (Entisols,
Inceptisols, Ultisols).
3 orders by unique vegetative influence
(Alfisols, Mollisols, Spodosols).
Resources
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http://soils.usda.gov/technical/soil_orders/
http://www.soils4teachers.org/lessons-andactivities
http://www.cals.uidaho.edu/soilorders/orders.
htm