Title: Soil Profiles and Horizons
1Soil Profiles and Horizons
2AcknowledgementThis work was supported in
part by the National Decentralized Water
Resources Capacity Development Project with
funding provided by the U.S. Environmental
Protection Agency through a Cooperative Agreement
(EPA No. CR827881-01-0) with Washington
University in St. Louis. The results have not
been reviewed by EPA or Washington University in
St. Louis. The views expressed in this
presentation are solely those of NCSU, and
University of Arkansas and EPA and Washington
University in St. Louis do not endorse any
products or commercial services mentioned in the
presentation.
3Citation
- -Lindbo, D.L., M. H. Stolt, R. Miles, and D. L.
Mokma. 2005. 3. Field Description of Soils Soil
Horizons Power Point Presentation. in (D.L.
Lindbo and N. E. Deal eds.) Model Decentralized
Wastewater Practitioner Curriculum. National
Decentralized Water Resources Capacity
Development Project. North Carolina State
University, Raleigh, NC.
4Soil Profile Language
- There is a standard nomenclature or language
used to describe soils - The ability to understand the nomenclature used
by soil scientists aids in communication between
the installer, designer, and regulator - Often the nomenclature will identify features in
the soil that have a direct bearing on soil
properties related to wastewater treatment and
dispersal
5Soil Profile Descriptions
- Soil Profile - A vertical section of the soil
extending through all its horizons and into the
parent material. - Soil Horizon - A layer of soil, approximately
parallel to the surface, having distinct
characteristics produced by soil forming
processes. - Soil Layer - A layer in the soil deposited by a
geologic force (wind, water, glaciers, oceans,
etc.) and not relating to soil forming process.
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7Soil Horizon Designations
- Soil horizons designated by a combination of
CAPITAL LETTERS-lower case letters-ARABIC
NUMERALS - Master Horizons and Layer Major breaks in the
soil O, A, E, B, C, and R. - Subordinate Distinctions Lower case letters
used as suffixes to designate specific master
horizons. i.e. Ap, Bw, Cg - Vertical Subdivisions A horizon designated by a
single combination of letters which needs to be
subdivided. i.e. Bw1, Bw2, Cg1, Cg2.
8Organic (O) Horizons
- O horizons or layers Layers dominated by
organic material. - Field Criteria
- 18 organic matter
- Dark color (never used by itself)
- Low strength, light dry weight, high fiber
content - Typically a surface horizon-if buried may
indicate disturbance - Subordinate Distinctions of O Horizon
- Oa-Highly decomposed organic material (Muck)
- Oe-Moderately decomposed organic material (Mucky
Peat) - Oi-Slightly decomposed organic material (Peat)
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16O Horizons Considerations
- Limitations to on-site wastewater
treatment/disposal - Fire hazard
- Low strength
- Low permeability
- Wet
- Limitation only when the O horizon is
sufficiently thick - Regardless of thickness the above limitations
still must be considered
17A Horizons
- Referred to as topsoil and typically ranging from
1-12 inches (2-30 cm) thick (may be more in
certain circumstances). Mineral horizon formed
at the surface or below an O horizon.
Characterized by an accumulation of humified
organic matter intimately mixed with the mineral
fraction. - Field Criteria
- Mineral soil material
- Mix of well decomposed organic matter and mineral
material - Surface mineral horizon
- Typically dark in color-darker than underlying
horizons - Typical Subordinate Distinctions of A Horizon
- Ap-Plowing or other disturbance
18A Horizon
19Ap Horizon
20A Horizon gradual boundary
21Clod from plow
22A Horizon Considerations
- Generally, suitable structure (granular)
- Offer high degree of treatment potential due to
higher OM content. - Evaluate and Ap for potential plow pan
- Evaluate for redoximorphic feature
- Redox concentrations-pore linings
- Redox depletions-low chroma areas
23E Horizons
- Mineral horizon in the upper part of the soil
typically underlying an O or A horizon. Light
colored, leached horizons ranging from not being
present to several centimeters thick - Field Criteria
- Zone of eluviation - removal of clays, Fe, Al,
and humus - Lighter in color than over or underlying horizon
- Near surface, below O or A horizons and above a B
horizon
24E Horizon (cont.)
- Formed by weak organic acids that strip coatings
(clay, OM, Fe, etc.) from sand grains. Light
color due to the natural color of the mineral
grains. - Subordinate Distinctions of E Horizons
- Eg-Strong gleying, indicates prolonged periods of
saturation - Ex-Fragipan dense, restrictive horizon
25E Horizon
26E Horizon
27E Horizon
28E Horizon
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30E Horizon Considerations
- Structure variable
- Must determine if the colors are due to leaching
or redox conditions or both - May restrict water movement
- Thickness-if restrictive can it be removed?
31B Horizons
- Referred to as subsoil. They are the zone of
accumulation with in the soil. In well drained
soils it has the brightest colors. May extend
over a meter below the surface.
32B horizon (cont.)
- Field Criteria
- Subsurface horizon formed below an O, A, E
horizon and above the C horizon - Formed as a result of soil forming processes
- Weakest expression is color development
- Illuvial concentration-zone of accumulation
- Single grained or weak structure not massive
- Subordinate Distinctions of B Horizons
- Bw-Development of color or structure
- Bt-Accumulation of clay
- Bg-Strong gleying, indicates prolonged periods of
saturation - Bh-Illuvial accumulation of humus
- Bs-Illuvial accumulation of sesquioxides
- Bm-Cementation or induration
- Bx-Fragipan dense, restrictive horizon
- Bv-Presence of plinthite
- Bss-slickensides
33Bw Horizon Considerations
- Weakly structured but not massive
- May contain redoximorphic features
34Bw Horizon
35Bw Horizon
36Bw Horizon
37Bt Horizon Considerations
- Higher clay content than overlying horizon
- Weakly to strongly structured
- May appear massive in auger borings
- Can restrict water movement even if no
redoximorphic features are present - May contain redoximorphic features particularly
around roots and ped faces
38Bt Horizon
39Clay Skin
40Bg Horizon Considerations
- Formed under saturated and reduced conditions
- Indicative of water table for long duration (gt 21
days) - May contain some redox concentrations
- Must have value gt4 and chroma lt2
41Bg Horizon
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44Bg Horizon
45Bh Horizon Considerations
- Hummus accumulation-feel greasy
- Primarily found in sandy textured soils
- May indicate high water table (Aquod) or not
(Orthod) - May or may not be restrictive to water movement
- Multiple Bh horizons may occur
46Bh Horizon
47Bh Horizon
48Bs Horizon Considerations
- Sesquioxde (Fe and Al-oxides) accumulation often
associated with Bh horizons - Primarily found in sandy textured soils
- May contain redoximorphic features
- May indicate high water table (Aquod) or not
(Orthod) - May or may not be restrictive to water movement
- Multiple Bs horizons may occur
49Bs Horizon
50Bs Horizon
51Bs Horizon
52Bss Horizon Considerations
- Formed by shrinking and swelling of clays.
- Low permeability
- Can disturb foundations etc.
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54Bss Horizon
55Bss Horizon
56Bm Horizon Considerations
- Cemented horizons
- Restrictive to water movement
- Variable thickness
57Bm Horizons
58Bm Horizon
59Bx Horizon Considerations
- Apparently cemented horizon but will slake in
water - Dense and brittle
- Appear massive but may have a secondary prismatic
structure - Restrictive to water movement often causing a
perched water table - May contain redoximorphic features
60Bx Horizon
61Seam
6230 cm (12 inches)
Plan View
63Bv Horizon Considerations
- Contains plintihite
- May be restrictive to water movement
64Plinthite
65Bv Horizon
66C Horizon
- Referred to as substratum. These horizons and
layers are little affected by soil forming
processes (unweathered geologic material). - Field Criteria
- Little affected by soil-forming processes
- Geologic layering
- Lack of color development, color of unweathered
geologic material - Subordinate Distinctions of C Horizons
- Cd-Dense unconsolidated sediment
- Cg-Strong gleying, indicates prolonged periods of
saturation - Cr-Weathered or soft bedrock
- Ck-Presence of carbonates
67C Horizon Considerations
- Shows little evidence of alteration yet can be
easily dug with a spade. - Water movement through it will be primarily
controlled by its texture - May or may not exhibit redoximorphic features
68 C horizon
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70C horizon
71C or Cr Horizon Considerations for Residual Soils
- Saprolite, can be dug with a spade
- May contain redoximorphic features
- May or may not be restrictive to water movement
72C horizon
73C horizon
74Cr horizon
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76Cd Horizon Considerations
- Dense, often massive
- May contain redoximorphic features
- Restrictive to water movement
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79Cg Horizon Considerations
- Formed under saturated and reduced conditions
- Indicative of water table for long duration (gt 21
days) - May contain some redox concentrations
80Cg Horizon
81Cg Horizon
82Ck Horizon Considerations
83R Horizons
- Bedrock that can not be dug with a spade
84Soil Surface
Lithologic Discontinuity or R horizon
85Transitional and Mixed Horizons
- Transitional horizons
- Combine master horizon designations
- i.e. AE is an horizon that is more A than E but
has characteristics of both, an EA is more E than
A - Mixed horizons
- Combine master horizons with a slash (/)
- i.e. A/E is an horizon with E material mixed into
dominantly A material
86A vs E horizon
- A horizons have a high OM content
- E horizons have low OM content
- E horizons often feel sandier (coarser) than the
A horizon - E horizons have a higher value and chroma
87E vs B horizon
- E horizons are sandier (coarser) than B horizons
- E horizons are higher in value and chroma
- B horizons have more clay
- B horizons have more Fe
88Examples
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95Fripp Series
96Ousley Series
97Stockade Series
98Goldsboro Series
99Rains Series
100Chewacla Series
101Dothan Series
102Wagram Series
103Appling Series
104Cecil Series
105Green Level Series
106Hiwassee Series
107Tate Series
108Buladean Series
109Biltmore Series
110Hayesville Series
111Burton Series
112Wayah Series