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Identifying “Problem” Hydric
Soils
Objectives
�Understand why “problem” hydric soils occur
�Be able to predict where problem hydric soils may occur
�Identify and document problem hydric soils
NC/NE Supplement Problematic Hydric Soils
1. Sandy soils2. Red parent materials3. Dark parent materials4. Fluvial deposits within floodplains5. Recently developed wetlands6. Seasonally ponded soils7. Wet soils with high chroma subsoils8. Discharge areas for iron-enriched
groundwater
Problematic Soil Indicators
A10 – 2 cm Muck A16 – Coast Prairie Redox
S3 – 2” Mucky Peat or Peat S7 – Dark Surface
S8 – Polyvalue Below Surface S9 – Thin Dark Surface
F12 – Iron/Manganese Masses F21 – Red Parent Material
TF12 – Very Shallow Dark Surface
Saturated, but not Reduced
�Low organic matter �e.g., sands
�No iron �e.g., E horizons of Spodosols, sands
�Oxygenated water �slopes, sands and gravels, “perched”
water tables�Cold temperatures�High pH, salinity
� problem in the West
Slope wetland in Glacier National Park
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Problem Hydric Soils
�Dark A horizons > 12” thick�Mostly Mollisols (Mollic epipedons)�Dark colors from high OM mask redox
features�Thick, sandy E horizons
�Most often Spodosols�Also Grossarenic Ultisols in the Southeast
�Lack of Fe in E horizon�Soils with little development
�Usually Entisols�Sandy soils, low OM, recent deposits on
floodplains
Problem Hydric Soils
�Parent materials�Reddish colored
�e.g., materials derived from glacial till deposits
�Gray colored�e.g., shale and dolomite parent materials
Soils with thick Dark Surfaces
� Most are Mollisols � Dark-colored mineral soils
with accumulation of OM in the upper part
� Generally prairie soils, but are extensive soils occurring in herbaceous wetlands throughout the U.S.
MOLLISOLS
Why a Problem?
�Lack redoximorphic features in upper part�redox features,
where present, are often masked by dark colors due to OM
�Commonly disturbed by tillage
Soils with Dark-Colored Surfaces
�Critical to look at the color of the B horizon� often more than 10” deep
�Whole profile color trends (dry to wet)�Hue - trend from red to yellow�Value and Chroma - decrease
�A horizon�becomes thicker, darker, yellower, some
redox�B horizon
�yellower, grayer, redox
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Soils with Dark-Colored Surfaces
�Color below Dark Surface �Edge effect *�Landscape position *
* Pertinent in all soils
“Tricks of the Trade”
Spodosols
� Mineral soils that have a spodic horizon.
� Amorphous mixtures of OM and Al, with or without Fe, have accumulated.
� Usually have a gray to light gray eluvial (E) horizon overlaying the
di
SPODOSOLS
Why a problem?
� Lack redoximorphic features in the upper part� Fe leached into lower
layers� sandy materials low in
OM� B horizon colors not
always diagnostic� Fe in upper B horizons
not responsive to oxidation / reduction reactions
Spodosols (what to look for)
�Surface layer of peat or muck�Black-colored mineral surface layer
�70% black, not salt and pepper�Splotchy, streaky, or “dirty” E horizon�High-chroma redox features in the E
horizon�Partly or wholly cemented spodic
(ortstein) within 12”�Gray colors below the spodic “Dark Surface Sand” Samples
90% 70% 50%
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Recently Deposited Soils
�mineral soils withlittle or no
horizon development
�young soils on unstable landscapes�e.g., floodplains
�sandy soils
Entisols
ENTISOLS
Why a Problem?
� Lack redoximorphic features in upper part� recently deposited
material�sandy materials
low in organic matter
� Colors can be “lithochromic”
Entisols - Two Divisions
� Fluvents and Fluvaquents - mostly loamy and clayey
� Psamments and Psammaquents - sandy
Udifluvent Udipsamment
Fluvaquents
�May have to rely on evidence of flooding�stratifications�USGS stream
gauge data�possibly chroma 3
with redox (A16)
Sandy Entisols
�Not necessarily “recent” origin
�Sandy parent material�little weatherable
minerals�lack of organic
matter
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Sandy Soils (what to look for)
�Same as Spodic surface layers�e.g., muck, peat, dark-colored mineral
layer�Blotchy colored subsoils
�stripped matrix�2.5Y or 5Y hues with 3-chroma matrix
and some redox features (A16)�caution, 3 chroma should not be inherited
from parent material
Problem Soils, Parent Material
�Gray colored�Lacustrine and alluvial
deposits�Dolomite and shale
parent materials
Problem Soils, Parent Material
�Reddish colored
�Great Lakes region glacial lacustrine and till deposits
Red soils get “browner” as they get wetter
Well drained
SWP drained
Poorly drained
Still not sure?�Landscape position, landscape
position…�compare soil profiles from various
landscape positions
�Look at the entire soil profile�top to bottom, not just 10” or immediately
below the A
Landscape Position
� Critically influences water flow and soil formation
� Most wetlands, even groundwater seeps, are on some sort of concave surface
Divergent
Convergent
Slope Block Contour
Hill Slope Elements and Curvature
Upslope
Upslope
After Pennock et al., 1987Overland and Throughflow:
Convergent landscapes
Throughflow
Runoff
InfiltrationPercolation
Potential hydric soilzone
“Epiaquic”
“Endoaquic”
Modified from Pennock et al., 1987
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Landscape Transect Approach
� Soils occur as a continuum on the landscape
� Describe a known “wet” soil
� Describe a known “upland” soil
� Use judgment to discern the boundary
Wettest UplandWet ???
Still not sure?�Indicators of wetland hydrology and a
hydrophytic plant community�herbaceous layer is often more diagnostic
than trees
�When all else fails....
… MONITOR !!Apply the technical
standard
… MONITOR !!Apply the technical
standardNC/NE Supplement
Procedure
1. Is hydrophytic vegetation present? If Yes, go to 2.
2. Is 1 primary or 2 secondary hydrology indicators present? If Yes, go to 3.
3. Will landscape position collect water? If Yes, go to 4.
4. The soil is hydric if:
NC/NE Supplement Procedure
a. Soils meet one of these indicators:(1) 2 cm muck (A10)(2) Coast prairie redox(A16) (3) 5 cm mucky peat or peat (S3)(4) Dark surface (S7)(5) Polyvalue below surface (S8)(6) Thin dark surface (S9)(7) Iron-manganese masses (F12)(8) Red parent material (F21)(9) Very shallow dark surface (TF12)
OR
NC/NE Supplement Procedure
b. One or more of these problematic soil situations is present:
1. Sandy soils2. Red parent materials3. Dark parent materials4. Fluvial deposits within floodplains5. Recently developed wetlands6. Seasonally ponded soils7. Wet soils with high chroma subsoils8. Discharge areas for iron-enriched groundwater
OR
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NC/NE Supplement Procedure
c. Soils changes color when exposed to air (4” layer starting within 12” of the surface: must have matrix value > 4 & chroma < 2 and become redder by > 1 hue page or chroma within 30 minutes)
ORd. Soil reacts to alpha, alpha-dipyridyl (4” within 12” of soil surface)
ORe. Gauge data, water-table monitoring data or direct hydrologic observations show ponding or flooding or high water table for 14 consecutive days
If YES to any of the above, soil is hydric. Mark “other” on data form and explain in remarks
Matrix 10YR 3/3
Mottles10 YR 5/1 &10YR 4/1