Soil Taxonomy- Properties 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 Desert soils have low

organic content. Grasslands have high

organic content.

The exact type of vegetation is also important because it also affects pH.

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

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

1) Orders (12)2) Suborders (54)3) Great Groups (211)4) Subgroups (1,100+)5) Family (7,000+)6) Series (a lot!)

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

This is the name of oneOf the 12 large categories

Mollisol - oll

Oder - root of order

Orders

Highest and most general of the soil classification system (similar to the phylum in plant taxonomy)

Based on conditions under which the soil developed

Fine-loamy mixed, superactive, mesic Aquic Argiudolls

Orderoll = Mollisols

Suborders

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

Fine-loamy mixed, superactive, mesic Aquic Argiudolls

SubOrder

Order

Ud = Udic Moisture

Great Groups (not required to know)

Based on differences between soil horizons

Fine-loamy mixed, superactive, mesic Aquic Argiudolls

GreatGroup

SubOrder

Order

Argi = Clay accumulation

Sub Groups (not required to know)

Describes a profile characteristic, wetness, sand, etc.

GreatGroup

Fine-loamy mixed, superactive, mesic Aquic Argiudolls

SubGroup

SubOrder

Order

Aquic = wet soil

Family (not required to know)

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

GreatGroup

Fine-loamy, mixed, superactive, mesic Aquic Argiudolls

FamilySubGroup

SubOrder

OrderTexture, clay minerals, CEC, temp,

Series (not required to know)

Named from the town or landscape feature near where the soil was first recognized (Eleva= Eleva, WI or Gale for Galesville, WI .)

GreatGroup

Fine-loamy mixed, superactive, mesic Aquic Argiudolls

FamilySubGroup

SubOrder

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

Entisol Inceptisol Andisols Spodosols Mollisols Alfisols Ultisols Oxisols Aridisols Vertisols Histosols Gelisols

The 12 Soil Orders

Orders with unique parent materials:

Andisols (and)

Volcanic ash soils.

Histosols (ist)

Organic soils.

Vertisols (ert)

High shrink/swell clay soils.

Orders formed in unique environments.

Aridisols (id)

Arid climates. CaCO3 accumulation

in subsoil.

Gelisols (el)

Colder climates. Permafrost layer

within 2 m of surface.

Oxisols (ox)

Tropics and subtropics.

Intensely weathered.

Orders by age.

Entisols (ent)

‘Baby’ soil. Little to no

morphological development.

Inceptisols (ept)

‘Toddler’ soils. Weakly developed

sub-surface horizons.

Ultisols (ult)

Older soils. “Ultimately

weathered”. Strongly leached. Sub-surface clay

accumulation. < 35% base sat. in

sub-soil.

Orders developed under unique vegetative ecosystems.

Alfisols (alf)

Forest soils. Usually an A-E-B

type horizon development.

The A horizon is usually less than 25 cm.

Mollisols (oll)

Grasslands soil. Thick, dark A

horizon. High % base

saturation.

Spodosols (od)

Acid forest soils. Usually sandy. Thick, bright white E

horizon. Sub-surface layer of

accumulated metal-humus complex (Bhs and Bs horizons).

Summary:

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

http://soils.usda.gov/technical/soil_orders/ http://www.soils4teachers.org/lessons-and-ac

tivities http://www.cals.uidaho.edu/soilorders/orders.

htm