Lecture 5a Soil Taxonomy

1. 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

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, mesicAquic 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 • 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, mesicAquic Argiudolls Order oll = Mollisols

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

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

7. Sub Groups (not required to know) • Describes a profile characteristic, wetness, sand, tonguing of E, etc. Fine-loamy mixed, superactive, mesicAquic Argiudolls Sub Order Sub Group Order Great Group Aquic = wet soil

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

9. 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.) Fine-loamy mixed, superactive, mesic Aquic Argiudolls Sub Order Sub Group Family Order Great Group

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

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

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

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 • 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. 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 1998 - 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 Orthent A 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