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Lecture 5a Soil 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.

1) 2) 3) 4) 5) 6)

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

Orders

Fine-loamy mixed, superactive, mesic Aquic Argiud olls   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 Argi udolls  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 Based on differences between soil horizons Great Sub Order Order Group Argi = Clay accumulation

Sub Groups

(not required to know)  Fine-loamy mixed, superactive, mesic Aquic Argiudolls Describes a profile characteristic, wetness, sand, tonguing of E, 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 , Sub Group Sub Order Great Group Order  Based on soil properties that affect management and root penetration, such as texture, temperature, and depth

Series = Le Sueur –

this is where the soils of the week names are from – ie Lester, Clarion, Nashwauk etc.

Fine-loamy mixed, superactive, mesic Aquic Argiudolls Family  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.) Sub Group Sub Order Great Group 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 thinner lighter color Mollic Histic more organic matter low base saturation Umbric

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

Oi E Bhs Bs 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

Spodic more Al and Fe very weathered Oxic Argillic Cambic less developed more sodium Natric

            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 carbonates, A Ochric + cambic or argillic or other diagnostic feature.

Bw Bk C

Aridisol in Idaho

A Bt Bk Bkqm R

Aridisol - Nevada

 NaCl Salt Az the surface and in the subsurface.

C1 C2

Mollisols - oll

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soils with thick, dark, soft surface - mollic + cambic, natric, argillic high base - soils of the or none saturation 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

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

Alfisol -- alf

  fertile forested soils with ochric and argillic forested soils high base saturation (> 35%) 7% of the world.

Ultisols - ult

  soils more weathered than Alfisols and argillic ochric - low base saturation < 35% - redder and more acid than Alfisols 8.5% of the world - less fertile than Alfisols Bt2 BC

Alfisol & Ultisol

Histosols - ist

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

Oe1 Oe2 Oe3 Oe4 Oa 2C 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 A A Bw Ab Bwb Andisol from Idaho Bw 2BC 2C 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

Oxisol

Ap1 Ap2 Bo1 Bo2 Bo3

Oxisol Puerto Rico

Ap A Bo1 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 Alfisol -Udalf -

Dropped in 1998

Entisol -

Boroll

- Aquoll - Ustoll

Boralf -

Aqualf Orthent - Psamment – Aquent Fluvent Inceptisol - Udept - Aquept Spodosol - Orthod Vertisol - Aquert Histosol - Fibrist - Hemist - Saprist

Suborder definitions

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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 Orthent A Bw Not Cambic due to being too sandy C

  Fluvent – Soils of the floodplains.

Lots of layers that are deposited when the river floods

Orthod

Minnesota Orthod Wisconsin Orthod A E Bhs Bs C

Udept - Aquept

EUTRUDEPTS

Aquert

Fibrist - Hemist - Saprist

Suborder Map You need to know the location of the suborders in Minnesota