1. Soil Properties Willie Harris apatite@ufl.edu Acknowledgments:
Wade Hurt
Mike Vepraskas
FAESS Soil Scientists
Website to download files of talks:
wgharris.ifas.ufl.edu.hsw.htm

2. Meaning of “Soil” Means different things to different people.
USDA definition … if it helps you to sleep.
Willie’s take on the USDA concept of soil:
Soil is material on landscapes that either:
Has horizons formed from processes that occurred since deposition or exposure, or
Has the in-place ability to support rooted plants.

3. Factors of Soil Formation
Parent Material
Time
Soil
Climate
Relief
Organisms

4. Floodplain
Young
Minimal development
Low terrace
“Middle aged”
Moderate development
High Terrace
Old
Maximal development

5. Soils as a Cosmic Experience - Evidence on a high hill that a
river once was there.

6. Difference Between Mineral and Organic Soil Material
Organic if: %OC ≥12% x % Clay

7. Degree of Organic Matter Decomposition
≥ 2/5 fibers (volume) after rubbing = Fibric
< 1/6 fibers (volume) after rubbing = Sapric
Intermediate = Hemic
Fibric = low degree of decomposition
Hemic = intermediate degree of decomposition
Sapric = high degree of decomposition

8. Properties used in describing soil layers
a. Color: A key property in hydric soil interpretation
Most evident
Influenced by OM and redox-sensitive metals
Wetness affects OM and redox-sensitive metals

9. Color is described using the Munsell Color Book
Here, the
book is opened
to the 10R
Page …

10. Hue:
Related to
Wavelength
Value:
Related to
reflectance
Chroma: Degree of spectral purity

11. Here, the
book is opened
to the 10YR
Page …
Notation works
Like this:
yellowish brown (10YR 5/6)
value
hue
chroma

12. Hue Red 0 2.5R 5R 7.5R 10R Yellow-Red 0 2.5YR 5YR 7.5YR 10YR Yellow
Hues highlighted in yellow are the common soil hues.
Y 5Y 7.5Y Y

13. Value The Lightness or Darkness of Spectral Color 10/0 - Pure White
5/0 - “Gray”
0/0 - Pure Black
The Lightness or Darkness of Spectral Color

14. Chroma “Neutral” “Pure” Color Color /0 /2 /4 /6 /8
/ / / / /8
Increasing strength of color
Increasing grayness

15. Reading Soil Colors Optimum conditions Natural light Clear, sunny day
Midday
Light at right angles
Soil moist

16. Contrast of Colors Faint -- evident only on close examination
Contrast refers to the degree of visual distinction between associated colors.
Faint -- evident only on close examination
Distinct -- readily seen
Prominent -- contrast strongly
Hydric soil indicators specify distinct or prominent.

17. Abundance and Size of Color Contrasting Areas
Few -- less than 2%
Common -- 2 to 20%
Many -- more than 20%
Fine -- < 5 mm
Medium -- 5 to 15 mm
Coarse -- > 15 mm
Abundance more important for Hydric Soils

18. b. Texture - proportions of sand, silt, and clay
The mineral component is usually described by it’s texture. Soil texture refers to the relative amounts of the variously sized soil separates. Where:
Gravel and larger fragments are >2 mm in diameter.
Sand is mm in diameter.
Silt is 0.05 to mm in diameter.
Clay is < mm in diameter.

19. Relative Sizes of Soil Particles
Sand ( mm)
Silt ( mm)
Clay (<0.002 mm)

20. USDA Textural Classes - Defined by “textural triangle”

21. “Basic” Soil Texture Triangle
Clay
Clayey
Loamy
Sandy
Sand
Silt

22. c. Structure: Way soil particles aggregate into larger units with planes of weakness between them. Individual aggregates called peds.
Common surface structure is granular: small spheroids
Examples of common subsurface structure:
Prismatic or
Columnar
Blocky
Platy

23. Soil Horizon Designations
Soil horizons are layers formed via soil processes
Master Horizons
O – High organic matter content; “organic soil material”!
A – Enriched in organic matter content; but not “organic soil material”!
– At surface or below O
– May be an “A” if disturbed (e.g., plowing)
E – Loss of fine-textured components; “eluviation”
– Characterized by clean sand, light color (high value, low chroma)
B – Accumulation of components translocated from above
– In-situ accumulation of metal oxides
– Other in-situ gains and losses
C – Little or no alteration; rock structure often evident
R – Rock

24. Transition Horizons

25. Subordinate Distinctions within master horizons
Convey information about soil genesis and disturbance
Designated by lower case. EX: Bt, Bw, Ap
Important ones for Florida:
Ap - plowed or disturbed surface
Bt - illuvial accumulation of clay
Btg - illuvial clay + iron reduction or depletion
Bh - illuvial accumulation of aluminum and carbon
Oi - fibric organic soil material
Oe - hemic organic soil material
Oa - sapric organic soil material

26. Horizon Boundaries

27. Bringin’ it all back home
A YR 3/1; sand; cw boundary
E YR 5/2; sand; gw boundary
E YR 7/1; sand; as boundary
Bh - 5 YR 2/1; sand; gw boundary
Btg YR 5/2; sandy clay loam;
gw boundary; blocky structure
Btg YR 6/2; sandy clay loam;
blocky structure