1. Soils Up Close: The Soil Profile and Horizon Characteristics

2. I. The Soil Profile A. Profiles vs
I. The Soil Profile A. Profiles vs. Pedons Soil Profile: a two-dimensional body, commonly studied in artificial cuts. Soil Pedon: a three-dimensional body, with the same thickness as a profile, but with a surface area that ranges between 1 and 100 square meters.
From: Birkeland, 1999

3. I. The Soil Profile
B. Gaining the 3rd Dimension

4. I. The Soil Profile
B. Gaining the 3rd Dimension
Roadcut/Construction Excavation

5. I. The Soil Profile
B. Gaining the 3rd Dimension
2. Pit Excavation

6. I. The Soil Profile
B. Gaining the 3rd Dimension
3. Soils Augering

7. The Soil Profile
C. Major Components of Soil

8. The Soil Profile
C. Major Components of Soil
Mineral Matter 45%
Organic Matter 05%
Water 25%
Air 25%

9. II. Soil Profile Horizons A. Master Horizons

10. I. The Soil Profile A. Master Horizons…… O A E B C R
Solum
Solum: Consists of the surface and subsoil layers
that have undergone the same soil forming conditions.
Epipedon: “over the soil"; the uppermost layer of
soil that serves as the diagnostic horizon.

12. E R

17. E

18. E

20. “Zone of Leaching” Or
“Zone of Eluviation”

21. Zone of illuviaton

22. Diagnostic properties (B horizon)
Thickness
Color
Texture
Structure

24. R

25. II. The Soil Profile C. Subhorizons

27. Subhorizons

28. Subhorizons

29. Subhorizons

30. Subhorizons

31. III. Soil Profile Characteristics

33. III. Soil Profile Characteristics
A. Texture

34. III. Soil Profile Characteristics A. Texture Major categories Boulder
Stones
Cobble
Gravel
Sand
Silt
Clay
600 mm
250 mm
76 mm
2 mm
0.05 mm
0.002 mm

37. < mm
Texture
2.0 to mm
0.062 to 0.05 mm

38. Texture < 0.002 mm Common in B Horizons Common in A Horizons
2.0 to mm
0.05 to mm
Common in A Horizons over Granites

39. III. Soil Profile Characteristics
A. Texture
2. Importance of Texture in Soils Work

40. III. Soil Profile Characteristics
A. Texture
2. Importance of Texture in Soils Work
Reflects character of Parent Material

41. III. Soil Profile Characteristics
A. Texture
2. Importance of Texture in Soils Work
Reflects character of Parent Material
Affects processes within the soil

42. III. Soil Profile Characteristics A. Texture
2. Importance of Texture in Soils Work
Reflects character of Parent Material
Affects processes within the soil
Degree of horizon development (fine vs. coarse-grained soils)
Drainage properties
Engineering properties

43. III. Soil Profile Characteristics A. Texture
2. Importance of Texture in Soils Work
Reflects character of Parent Material
Affects processes within the soil
Degree of horizon development
Drainage properties
Engineering properties
Degree of chemical reactivity
Water retention

44. III. Soil Profile Characteristics A. Texture
2. Importance of Texture in Soils Work
Reflects character of Parent Material
Affects processes within the soil
Degree of horizon development
Drainage properties
Engineering properties
Degree of chemical reactivity
Water retention
Erositivity
Tilth

45. III. Soil Profile Characteristics
A. Texture
3. Determining Texture

46. Qualitative Methods

47. Qualitative Methods

48. III. Soil Profile Characteristics
A. Texture
3. Determining Texture

49. III. Soil Profile Characteristics
A. Texture
3. Determining Texture

50. 20 ml
pipette

52. Determine the settling velocity of a clay particle.
Given:
Clay = mm
Ρw = 1.00 gm/cm3
ρs = 2.70 gm/cm3
µ = * 10-3 (kg/m*s)
g = 981 cm/s2
Find V

54. III. Soil Profile Characteristics B. Color
1.Mechanics
Munsell Color Chart
Hue
Value
Chroma

55. III. Soil Profile Characteristics B. Color
Hue: Actual color of the soil relative to
The primary colors.
7.5 YR is 75% yellow, 25% red

56. III. Soil Profile Characteristics B. Color
Value: Lightness or darkness of color.
Value of 8 will be very light, whereas
Value of 2 is dark.

57. III. Soil Profile Characteristics B. Color
Chroma: Strength of color, e.g., the
amount of pigment in the sample.
A chroma of 7 reflects intense color,
whereas a chroma of 2 exhibits a
weak color.

58. Hue
LIGHT/DARK
(VALUE)
PIGMENTATION
(COLOR)
Munsell Color Chart

60. 2. The Application of Munsell Colors
a. Good Drainage (Well Drained)
Oxidizing Conditions
Yellow-Brown-Red Colors
Fe 2+ → Fe 3+

61. 2. The Application of Munsell Colors
a. Good Drainage (Well Drained)
Oxidizing Conditions
Yellow-Brown-Red Colors
Fe 2+ → Fe 3+

63. 2. The Application of Munsell Colors
b. Poor Drainage (Reducing Conditions)
Greyish-green-blue Colors
“Gleyed Colors”
Fe 3+ → Fe 2+
Hues > 5Y or “Gleyed Page”
of Munsell Chart
Low Chromas (~1)
“Mottles or Redox Features”

67. “Mottles or Redox Features”

68. Soil Colloids

69. III. Soil Profile Characteristics
C. Structure

70. III. Soil Profile Characteristics
C. Structure
In General:
An aggregation of soil particles called peds

71. III. Soil Profile Characteristics
C. Structure
2. Significance
Critical in soil drainage (determines infiltration rates)
Aeration, root penetration, nutrient retention, tilth
Related to genesis and rock type

72. III. Soil Profile Characteristics
C. Structure
3. Types/Categories

73. Common in A Horizon in VA
Loose/Granular
Sand A
Sand and Organics
E,Bx Km
Bq,Bm Bs
Soil Drainage Problems Bt
Well drained, well developed
soils in Virginia Bt Bn
Related to alkaline
(salty) soils, and/or
expansive clays Bt

75. “Durability”
Very Fine
Fine
Medium
Coarse
Very Coarse

78. Very Fine
Fine
Medium
Coarse
Very Coarse

83. III. Soil Profile Characteristics
D. Organic Matter

84. III. Soil Profile Characteristics
D. Organic Matter
What is it, and where is it found?
Underdecomposed plant and animal tissue
Humus (“colloidal soil organic matter that decomposes slowly and colors soils brown or black”) from Birkeland, 1999

85. III. Soil Profile Characteristics
D. Organic Matter
…..where is it found?

86. III. Soil Profile Characteristics
D. Organic Matter
2. Importance
Increases water holding capacity and tilth
Increases cation exchange capacity (nutrient holding capacity)

87. 2. Importance
Increases water holding capacity and tilth
Increases cation exchange capacity (nutrient holding capacity)
Produces chelating compounds (organic acids) that increase solubility of ions
Releases high amounts of carbon dioxide, which accelerates chemical weathering
Sources of CO2:
--atmosphere (0.03% concentration)
--soils ( % concentration)

88. III. Soil Profile Characteristics E
III. Soil Profile Characteristics E. Bulk Density A measure of the weigh of soil per unit volume Important for studying soil moisture movement rates and rates of clay and carbon accumulation (pedogenesis)

89. IV. The Larger View
The value of solid profile descriptions (qualitative and quantitative)

90. Harden Indices