1. Soil Morphology and Classification

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

3. Reactivity of mineral and organic colloids
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 Texture Structure Density Water Acidity 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. Organisms/Vegetation
Factors Affecting Soil Formation
The 5 soil forming factors
Climate
Organisms/Vegetation
Parent material
Topography
Time

7. Temperature and Precipitation
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.)
The mineral content of leaves, limbs, stems of vegetation influences the soil character and particularly acidity. Pines tend to be low in calcium, magnesium, potassium reducing nutrient cyclinig compared to deciduous trees.

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 Water Erosion Vegetation Slope Aspect
Configuration of land surface – elevation, slope, depressions
Hastens or delays climatic forces.
Impacts depth of profile development.
Water
Erosion
Vegetation
Slope
Aspect
Standing versus removal of water, erosion on slopes, accumulation in depressions.

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

12. Stable, older sediments
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. Subordinate Distinction (g = gleying)
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+
Photographs showing redoximorphic features (soil mottling) which are color patterns in the soil formed by the oxidation and reduction of iron and/or manganese caused by saturated conditions within the soil. Redoximorphic features are used to estimate the depth to seasonal high watertable
oxidized
gleyed
material
Fe2+

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

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

24. o = oxic horizon Subordinate Distinction Low activity clays
Few weatherable materials
Little rock structure
Fe and Al oxides
The oxic horizon has:           a. a CEC7  < 16cmol(+)/kg of clay and an ECEC < 12 cmol(+)/kg of clay which is due to the low activity clay minerals (1:1 clays, Fe and Al oxides, etc)           b.  < 10% weatherable minerals in the sand fraction           c.  < 5% rock structure

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. Subordinate symbols: g, h, p, t, w and a,e,i
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
Characterized by similar master and/or subordinate
properties separated by “degree”.
Bt horizons
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…
1935, 1949,1965 comprehensive and shared by 43 other countries,
Genesis
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 strongly developed
Organic carbon = organic matter x 0.57

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

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

45. Ochric Epipedon Too: thin light Mollic low in O.M 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

51. Organic Matter Accumulation
O.M. accumulation
Histic
Mollic, Umbric
ochric
time
Parent
material
Vegetation
established
tmax = 3000 yrs

52. Diagnostic Sub-surface Horizons

53. Diagnostic Subsurface Horizons
Formation
Translocation
Transformation
Clays Organic Matter Oxides

54. Subsurface Horizons Organic Matter Clays Oxides Formation
Translocation
Transformation
Subsurface Horizons
Organic Matter Clays Oxides
Dark colors
Metals (Fe, Al)
smectites
Iron
Aluminum
Kaolinite
Also: salts, carbonates, sulfides

55. Diagnostic Subsurface Horizons
Albic
Argillic
Spodic
Oxic
Kandic
Cambic
Sombric
sulfuric
Natric
Agric
Calcic
Gypsic
Salic
Duripan
Fragipan
Placic
Sub-Horizon Designations

56. Diagnostic Subsurface Horizons
Albic (white) Horizon
Light-colored (Value > 6 moist )
Elluvial (E master horizon*)
Low in clay, Fe and Al oxides
Generally sandy textured
Low chemical reactivity (low CEC)
Typically overlies Bh or Bt horizons
albic
*not all E horizons are albic horizons

57. Diagnostic Subsurface Horizons
Argillic Horizon
Illuvial accumulation of silicate clays
Illuvial based on overlying horizon
Clay bridges
Clay coatings
Accumulation based on absolute increases compared to relevant horizon above or below. Argillic horizon. An argillic horizon is an illuvial horizon in which layer-silicate clays have accumulated to a significant extent by illuviation. They have formed below the surface of a mineral soil but may be exposed at the surface by erosion. In general, this is a B horizon which has an increase in clay content of at least 1.2 times that of the eluvial horizon above and is, in general, parallel to the surface of the polypedon. This increase of 20% in clay content occurs most in soils within a vertical distance of less than 30 cm. In case of clayey soils, this requirement would be unreasonable. If the surface horizon is greater than 40% clay, the increase of clay needed is only 8%. For sandy soils with less than 15% clay, an increase of 3% is required for meeting the criteria of an argillic horizon. In other words, if the clay content of the eluvial horizon is between 15 and 40%, an increase in clay of 20% is needed to meet the requirements for an argillic horizon.

58. Diagnostic Subsurface Horizons
Argillic Horizon
Kandic Horizon
High
Low
Activity of Clays
Necessary
Illuviation of clay
Not Necessary

59. Diagnostic Subsurface Horizons
Spodic Horizon
Illuvial accumulation of organic matter
and aluminum (+/- iron)
Dark colored (value, chroma < 3)
Low base saturation (acidic)
Formed under humid acid conditions
Spodic

60. Elluviation and Illuviation
Elluviation (E horizon and A horizons)
Organic matter
Clays A Bt A E Bh E
Bh horizon
Bt horizon
Spodic horizon
Argillic horizon

61. Diagnostic Subsurface Horizons
Oxic horizon
Highly weathered (high temperatures, high rainfall)
- High in Fe, Al oxides
- High in low-activity clays (kaolinite < smectite < vermiculite)
activity

62. Diagnostic Horizons Epipedons Subsurface Mollic Umbric Ochric Histic
Melanic
Plaggen
Anthropic
Albic
Kandic
Argillic
Spodic
Oxic

63. Soil Taxonomy Diagnostic Epipedons Diagnostic Subsurface horizons
Moisture Regimes
Temperature Regimes