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

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, tonguing of E, 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 = Le Sueur – this is where the soils of the week names are from – ie Lester, Clarion, Nashwauk

etc.

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.)

GreatGroup

Fine-loamy mixed, superactive, mesic Aquic Argiudolls

FamilySubGroup

SubOrder

Order

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

Soil Taxonomy- Diagnostic Surface Epipedons

Mollic Epipedon - thick, dark, soft, surface layer.

Characteristics Thick - greater than 10

inches; High base saturation> 50%;

Mineral soil Soils formed under

prairie vegetation

Other Epipedons Umbric - like

mollic, but low base saturation

Histic - Organic Soil - saturated with water, > -% organic matter

Ochric - thin, light colored - surface layers that do not fit any of the above

Base Saturation = relative amount of bases (Ca, Mg, K)in the soil,Low %= few, high% = many

Comparison of Epipedons

Ochric Histic

Mollic

Umbric

thinner

lighter color

more organicmatter

low basesaturation

Diagnostic Subsurface Horizons Argillic - illuvial

horizon of clay accumulation - Bt

Natric - same as argillic but with > 15% exchangeable sodium (Na) - Btn

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 or Bhsm

OiEBhsBs

C

subsurface horizons (cont.)

Oxic - very weathered layer of only Fe and Al oxides and 1:1 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

Comparison of Subsurface Diagnostic Horizons

Oxic

very weathered

Spodic Cambic

Argillic

Natric

more Al and Fe

less developed

more sodium

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

Entisol - ent

Recent soils - minimal development, little horizonation, young soils.

12.5% of world, Ochric + none

Entisol - Idaho

A

R

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

Vertisol = Bss at slickenslide

Inceptisol - ept

Inception - soil shows the beginning of horizon development, little or no illuviation,

15.8% of world, Ochric or Umbric + cambic.

Inceptisol

Soil Formed in colluvial material in mountains of Idaho.

Aridisols - id

Arid regions of the world (19%), < 10 in. of rainfall, usually contain carbonates,

Ochric + cambic or argillic or other diagnostic feature.

A

Bw

Bk

C

Aridisol in Idaho

ABt

BkBkqm

R

Aridisol - Nevada

AzBzC1

C2

NaCl Salt accumulates on the surface and in the subsurface.

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

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.

A1A2BwBCR

Spodosols- od

acid sandy soils with thick E and red Bhs - ochric and spodic -

5.4 % of the world - infertile soils.

OiE

Bhs

Bs

C

Alfisol -- alf

fertile forested soils with ochric and argillic - high base saturation (> 35%) - forested soils

7% of the world.

Ultisols - ult

soils more weathered than Alfisols - ochric and argillic - low base saturation < 35% - redder and more acid than Alfisols

8.5% of the world - less fertile than Alfisols

AE

Bt1

Bt2

BC

Alfisol & Ultisol

Histosols - ist

peat soils - organic material - histic

0.8% of the world Histic Epipedon.

Oe1

Oe2

Oe3

Oe4

Oa2C

Photo USDA

Dyad

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

Andisols - and

soils from volcanic ash - very light - low bulk density –

1% or the world

Andisol from Idaho

A

Bw

2BC

2C

ABwAbBwb

Ab’

Oxisols - ox

Soils with Oxic horizon - very weathered - soils of the tropics. low pH - acid soils - high in 1:1 clay minerals

9.2% of world

OxisolAp1

Ap2

Bo1

Bo2

Bo3

Oxisol Puerto Rico

ApABo1

Bo2

BC

C

Gelisol - el

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

Cf - horizon

Soil Orders USA

Soil Orders in Minnesota

Soil Orders – Wisconsin & Northern Illinois

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

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

Udoll - Ustoll - Aquoll

Ustoll

Udalf - Boralf - Aqualf

Orthent - Psamment – Aquent - Fluvent

A

Bw

C

Orthent

Not Cambic due to being too sandy

Fluvent – Soils of the floodplains.

Lots of layers that are deposited when the river floods

OrthodWisconsin Orthod

A

E

Bhs

Bs

C

Minnesota Orthod

Udept - Aquept

EUTRUDEPTS

Aquert

Fibrist - Hemist - Saprist

Suborder Map

You need to know the location of the suborders in Minnesota