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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