Soil Profile

1. Soil Profile

3. Soil genetic horizons -HORIZON: soil layer parallel to surface with characteristics produced by soil-forming processes

4. 3 basic soil units (scale) Pedon: smallest volume called a soil Polypedon: soil body (2 or more pedons) in which soils are relatively uniform Soil Series: groups of like polypedons

5. profile: one side of pedon, showing all horizons; 2-D

8. Master horizons O A E B C R Not every soil has all of these!!!

9. O horizon Organic material Same as litter layer or “duff”

10. Oi slightly decomposed (litter) : FIBRIC Oe intermediate decomposition: HEMIC Oa highly decomposed : SAPRIC Oi Oe Oa

12. A horizon (“TOPSOIL”) • topmost mineral horizon accumulation of well-decomposed O.M. • Often bioturbated • surface horizon disturbed by plowing (Ap)

13. Field trip: • Ap : Agassiz clay, drumlin, prairie

14. A horizon in grassland

15. Buried A horizon Ab

17. E horizon • LOSS of • silicate clay, Fe & Al oxides, humus by eluviation • carbonates, gypsum by leaching

18. Leaching vs. eluviation LEACHING: removal of soluble minerals (Ca, Mg, Na) in solution ELUVIATION: loss (by water) of suspended materials (clay, humus, oxides) ”emigrating”

19. E horizon • lighter color than A • Because the colorful humus and Fe, Al oxides have eluviated away • coarser texture than B • Because the clay eluviated away

20. E horizon in forest soil

23. B horizon • ACCUMULATED (illuviated ) ”immigration” silicate clay, Fe & Al oxides, carbonates, gypsum, humus • distinguished from A or E: • stronger, redder, or darker color • OR different texture

25. Bh Has illuviated humus from E (dark, brown or black stain at top of B) Bs Has illuviatedsesquioxides of Fe, Al from E (reddish color at top of B) Bhs Has both

27. E Bhs

28. O A E Bh Bs

29. Bw Bhs E

30. Bhs

31. A E Bhs

32. A E Bhs Bw

33. Bt An accumulation of silicate clay in B Can recognize it if you have clay in the B but not as much clay in the A Look at textures for drumlin, prairie, Agassiz clay (soybean field)

34. Bk Has precipitated carbonates in it; White nodules or streaks Strongly effervescent

36. w : used if you see a change in B that is not accounted for by other subhorizon letters • Bw If you see changes in color, texture, structure within a B

39. C horizon • Mineral horizon (not bedrock) underlying A,E,B horizons • not affected by soil-forming processes • may be parent material

41. C in field trip cores? • If you had only coarse sand and rocks (with no clay or silt) in bottom of cores in drumlin, you may have hit till (C) • Bottom of cores in Agassiz clay may have ben lake clay (C)

42. R horizon Consolidated rock

43. Transitional horizons Zone of transition between master horizons AB A B; A dominates BA A B; B dominates AC A C; A dominates EB E B; E dominates etc….

45. Mixed horizons One horizon scattered within another horizon B/A mixed A&B; B is matrix for A E/B E is matrix etc….

47. Numbers after letters Changes within master horizon for which there is no subhorizon designation e.g., A1 A2 for color change within A

49. Additional subhorizons that you will need to know: g ss o n