Soil Morphology and Classification

1. Soil Morphology and Classification

2. Purpose The Language of Soils Loamy, siliceous, hyperthermic grossarenic paleudult

3. Morphology and Classification of Soils Based on physical and chemical properties Color Texture Structure Density/Porosity Water Movement Reactivity of mineral and organic colloids Soil acidity and pH

4. Color Dark/grayish-black color Orange vs. Gray colors Texture Sandy vs. Clayey Structure Good vs. Poor Structure Density Porosity, organic matter, compaction Water Pore sizes, porosity, water movement, saturation Reactivity Cation exchange capacity Acidity Plant tolerances, buffering, base saturation All are used to classify soils

5. Soil Formation

6. Factors Affecting Soil Formation The 5 soil forming factors Climate Organisms/Vegetation Parent material Topography Time

7. Climate Temperature and Precipitation Rates of chemical, physical, biological processes Cold dry climates – weak to modest profile development Warm, humid climates – strong, deep profile development

8. Organisms/Vegetation O.M. accumulation Profile mixing Nutrient cycling Soil structure Soil solution (% B.S.)

9. Parent Material Affects texture, vegetation, nutrients clay mineralogy, CEC Deposition Colluvial (gravity) Alluvial (streams) Marine (oceans) Lacustrine (lakes) Glacial (ice) Eolian (wind) silt and clay

10. Topography Configuration of land surface – elevation, slope, depressions Hastens or delays climatic forces. Impacts depth of profile development. Water Erosion Vegetation Slope Aspect

11. Time Duration of weathering and all other factors Additions losses translocations transformations

12. McCarty Hall Stable, older sediments E Shands Hawthorne Formation (geologic Clay) Younger sediments Limestone

13. Soil Horizons: first step in classification

14. Soil Horizon designations O horizon • Master Horizons • O organic • A topsoil, O.M., cycling • E elluvial • B developed/accumulation • C parent material • R bedrock A horizon Organic matter E horizon Sandy B horizon Clays/iron C horizon Parent

15. Master Horizons Enough information? O horizon A horizon R horizon E horizon (Elluvial) C horizon B horizon B horizon (Illuvial)

16. Subordinate Distinctions

17. Subordinate Distinctions b – buried horizon c – concretions d – root restrictive g – gleying h – illuvial organic matter k – carbonates m – cementation o - oxic p – plowing/disturbance q – secondary silica r – soft bedrock (saprolite) s – illuvial sesquioxides and O.M. t – clay accumulation v – plinthite w – development of color/structure x - fragipan

18. Subordinate Distinctions g – gleying h – illuvial organic matter p – plowing/disturbance t – clay accumulation w – development of color/structure o – oxic

19. (g = gleying) Subordinate Distinction • Oxygen deprived or reduced state due to water saturation. • Reduction of iron (Fe III to Fe II) • low chroma • Often used with B master horizon (Bg horizon), also E and C horizon. oxidized material Fe3+ oxidized gleyed material Fe2+

20. h = organic accumulation Subordinate Distinction • Accumulation of illuvial organic matter-metal complexes • Coatings on sand and discrete particles • h = “humic” • value and chroma approximately 3 or less • Used with the B master horizon (e.g. Bh horizon) * Bh horizon “spodic horizon”

21. p = plowed Subordinate Distinction Disturbed surface horizon (cultivation, pasture, forestry) Used with the A master horizon (e.g. Ap horizon) Ap horizon

22. t = clay accumulation Subordinate Distinction Translocation of clay or formed in place Coatings or discrete Used with the B master horizon (e.g. Bt) If reduced, can be used with the g sub horizon (Btg)

23. w = color or structure Subordinate Distinction Non-illuvial development of color or structure “w” can = “weak” Commonly used with the B master horizon (e.g. Bw) Bw

24. Subordinate Distinction o = oxic horizon Low activity clays Few weatherable materials Little rock structure Fe and Al oxides

25. Subordinate Distinctions g – gleying h – illuvial organic matter p – plowing/disturbance t – clay accumulation w – development of color/structure o – oxic

26. Subordinate Distinctions and Organic Matter

27. a, e, i Subordinate Distinction Denotes the degree of organic matter decomposition in the O horizon. Oa – highly decomposed (sapric) Oe – moderately decomposed (hemic) Oi – slightly decomposed (fibric) Sapric –most decomposed, low plant fiber, low water content Hemic – intermediate decompostion Fibric – least decomposed, recognizable fibers

28. Summary Master: O, A, E, B, C, R Subordinate symbols: g, h, p, t, w and a,e,i Examples: Oa, Oe, Oi Bt Bg Btg Bw Ap

29. Other Designations

30. Vertical Subdivisions Bt horizons Characterized by similar master and/or subordinate properties separated by “degree”. Bt1 Bt2 Bt3

31. Transitional Horizons Transitional layers between master horizons. AE EB BE Dominant character Subordinate Character

32. Ap AE E Bh Bt Btg1 Btg2 Synthesis

33. Soil Taxonomy

34. Soil Classification/Taxonomy Hierarchical Soil Profile Based on soil profile characteristics and the concept of soils as a natural body. Observable properties: color, texture, structure, pH, O.M… Genesis 1883 V.V. Dukachaev: climate, vegetation, soil 1927 C.F. Marbut (USDA) applied to U.S. (1965)

35. Soil Classification/Taxonomy USDA classification system Soil Survey Staff 1965 Soil Taxonomy published 1975 • Adamsville: Hyperthermic, uncoated Aquic Quartzipsamment

36. Soil Taxonomy Hierarchy Kingdom Phylum Class Order Family Genus Species Order Suborder Great group Sub group Family Series 12 63 250 1400 8000 19,000

37. Units for Soil Classification Pedon – smallest three-dimensional unit that displays the full range of properties characteristic of a given soil. (1-10 m2 of area) - the fundamental unit of soil classification Polypedon – group of closely associated pedons in the field Soil Series – class of soils world-wide which share a common suite of soil profile properties

38. Soil Sampling Units Malabar Series

39. Diagnostic Horizons for Classification Surface Subsurface

40. Diagnostic Surface Horizons Epipedons Mollic Umbric Ochric Histic Melanic Plaggen Anthropic

41. Diagnostic Surface Horizons X = Florida Melanic X Plaggen Mollic Histic X Umbric Anthropic X Ochric X

42. Mollic Epipedon Thickness > 18-25 cm Color value < 3.5 moist chroma < 3.5 moist Organic Carbon > 0.6 % Base Saturation > 50 % Structure stronglydeveloped Organic carbon = organic matter x 0.57

43. View Tim Kiser's map Taken in Elkhart, Iowa (See more photos here) 41°27' 04" N, 93°31' 52" W41.451073-93.530988

44. Umbric Epipedon Meets all criteria of the Mollic epipedon, except base saturation < 50% Chemically different than Mollic

45. Ochric Epipedon Too: thin light low in O.M Mollic Umbric Ochric = pale Extremely common

46. Histic Epipedon Organic horizon Formed in wet areas Black to dark brown Low bulk density 20-30 cm thick Organic = > 20% - 35% O.M. (water saturation, clay content)

47. Melanic Epipedon Similar in properties to Mollic Formed in volcanic ash Lightweight, Fluffy

48. Anthropic Horizon • Resembles mollic • (color, o.m.) • Use by humans • Shells and bones • Water from humans

49. Plaggen Epipedon Produced by long-term (100s yrs.) manuring Old, human-made surface horizon Absent in U.S. > 50 cm thick

50. Diagnostic Surface Horizons Epipedons Mollic Umbric Ochric Histic Melanic Plaggen Anthropic Very common “specialized” Human-derived