1. 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

2. 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.

3. 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

4. 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

5. Suborders
Fine-loamy mixed, superactive, mesic Aquic Argiudolls
Sub
Order
Grouped by similarities in soil formation such as wetter/dryer soil, colder/warmer soil, etc.
Ud = Udic Moisture

6. Great Groups (not required to know)
Fine-loamy mixed, superactive, mesic Aquic Argiudolls
Sub
Order
Order
Great
Group
Based on differences between soil horizons
Argi = Clay
accumulation

7. Sub Groups (not required to know)
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

8. Family (not required to know)
Fine-loamy, mixed, superactive, mesic Aquic Argiudolls
Sub
Order
Sub
Group
Family
Texture, clay minerals, CEC, temp,
Order
Great
Group
Based on soil properties that affect management and root penetration, such as texture, temperature, and depth

9. 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
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.)

10. 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

11. 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

12. 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

13. Comparison of Epipedons
Ochric
Histic
Mollic
Umbric
thinner
lighter
color
more
organic
matter
low base
saturation

14. Diagnostic Subsurface Horizons
Argillic - illuvial horizon of clay accumulation - Bt
Natric - same as argillic but with > 15% exchangeable sodium (Na) - Btn

15. 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

16. 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

17. Comparison of Subsurface Diagnostic Horizons
Spodic
Cambic
less
developed
more Al
and Fe
Argillic
very
weathered
more sodium
Oxic
Natric

18. 12 Soil Orders - Each Order has a diagnostic epipedon and subsurface horizons – which could be “none”. WEB SITE for soil orders =
Entisol
Inceptisol
Andisols
Spodosols
Mollisols
Alfisols
Ultisols
Oxisols
Aridisols
Vertisols
Histosols
Gelisols

19. Entisol - ent
Recent soils - minimal development, little horizonation, young soils.
12.5% of world, Ochric + none

20. Entisol - Idaho A R

21. Vertisol - ert Mollic or Ochric + none
Inverted - soils with high clay content,
Large shrink swell potential
gradually invert on themselves,
2.1% of the world,
Mollic or Ochric +
none

22. Vertisol = Bss at slickenslide
soil cracks
Slickenslide

23. Inceptisol - ept
Inception - soil shows the beginning of horizon development, little or no illuviation,
15.8% of world, Ochric or Umbric + cambic.

24. Inceptisol
Soil Formed in colluvial material in mountains of Idaho.

25. 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

26. Aridisol in Idaho A Bt Bk
Bkqm R

27. Az Bz C1 C2 Aridisol - Nevada
NaCl Salt accumulates on the surface and in the subsurface. Az Bz C1 C2

28. 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

29. 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

30. 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

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

32. 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 A E
Bt1
Bt2 BC

33. Alfisol & Ultisol

34. Histosols - ist peat soils - organic material - histic
0.8% of the world
Histic Epipedon.
Oe1
Oe2
Oe3
Oe4 Oa 2C
Photo USDA

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

36. 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

37. 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

38. Oxisol
Ap1
Ap2
Bo1
Bo2
Bo3

39. Oxisol Puerto Rico Ap A
Bo1
Bo2 BC C

40. Gelisol - el
New Order as of soils with permafrost (formerly Cryochrepts - or frozen Inceptisols)
Cf - horizon

41. Soil Orders USA

42. Soil Orders in Minnesota

43. Soil Orders – Wisconsin & Northern Illinois

44. 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

45. 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

46. Udoll - Ustoll - Aquoll
Ustoll

47. Udalf - Boralf - Aqualf

48. Orthent - Psamment – Aquent - FluventBw C
Not Cambic due to being too sandy

49. Fluvent – Soils of the floodplains.
Lots of layers that are deposited when the river floods

50. Orthod
Minnesota Orthod
Wisconsin Orthod A E
Bhs Bs C

51. Udept - Aquept
EUTRUDEPTS

52. Aquert

53. Fibrist - Hemist - Saprist

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

55. What is the soil order here? -->
Entisol
The End