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Lecture 5a Soil Taxonomy

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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 - Fluvent
Bw 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

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