Basic Soils

8/13/2019 Basic Soils

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Soil Basics for DescribingSoil Basics for Describing

Wetland SoilsWetland Soils

Soil ColorSoil ColorColor is just about the mostColor is just about the most

importantimportant charactisticscharactistics to describeto describe

in a wetland soilin a wetland soil

It is influenced by:It is influenced by:

organic matter content,organic matter content,amount and type of Fe minerals,amount and type of Fe minerals,

moisture contentmoisture content


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-OM

-Fe -OM+Fe

Dr. Martin Rabenhorst

Ap Horizon

-OM

-Fe -OM+Fe

Bt Horizon

Dr. Martin Rabenhorst


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Moist ColorMoist Color

All colorAll colorrequirements (hue,requirements (hue,value, and chroma)value, and chroma)are for moist color.are for moist color.

Features areFeatures areusually more readilyusually more readilyidentifiable in moistidentifiable in moiststate; they may bestate; they may bemissing if soil is toomissing if soil is toowet (let dry).wet (let dry).

Munsell Soil ColorMunsell Soil Color


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Elements of soil colorElements of soil color

HueHue

ValueValue

ChromaChroma

HueHue Hue is created by theHue is created by the wavelengthwavelength of theof the

light rays. Think of it as one of thelight rays. Think of it as one of the

rainbow colors.rainbow colors.

Common soil hues are R (red), YRCommon soil hues are R (red), YR

(yellow(yellow--red), and Y (yellow).red), and Y (yellow).

Other hues found on gleyed pages are NOther hues found on gleyed pages are N

(neutral), GY (green(neutral), GY (green--yellow), G (green), Byellow), G (green), B

(blue), and PB (purple(blue), and PB (purple--blue)blue)


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Gradation of huesGradation of hues

Soil color hues can be expressed as 2.5,Soil color hues can be expressed as 2.5,

5, 7.5 and 10.5, 7.5 and 10.

A 5 hue (i.e. 5Y) is the purest of that hueA 5 hue (i.e. 5Y) is the purest of that hue

(all yellow).(all yellow).

As you go higher or lower you get mixturesAs you go higher or lower you get mixtures

of other hues (YR is yellowish red).of other hues (YR is yellowish red).

Hue in the Munsell Soil Color ChartHue in the Munsell Soil Color Chart


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GleyGley HuesHues

Grayish, Bluish, andGrayish, Bluish, and

GreenishGreenish

Hues on theHues on the GleyGley PagePage

Gley Hues

Gleyed Matrix


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Value: amount of light reflected

10/0 = Pure White

5/0 = Gray

0/0 = Pure Black

All light

reflected

No lightreflected

Much lightreflected

Little light

reflected


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ChromaChroma: concentration of hue: concentration of hue

Neutral Color PureNeutral Color Pure

ColorColor

____|________|______|______|_______|______|________|______|______|_______|__

__

/0 /2 /4 /6 /8/0 /2 /4 /6 /8

Increasing concentration of hueIncreasing concentration of hue -------->>


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Common Names and Notations givenCommon Names and Notations given

on lefton left--hand side of open bookhand side of open book

MunsellMunsell notation vs. English namenotation vs. English name

10 R 6/6 LIGHT RED10 R 6/6 LIGHT RED

10 R 6/8 LIGHT RED10 R 6/8 LIGHT RED

2.5 YR 6/8 LIGHT RED2.5 YR 6/8 LIGHT RED

7.5 YR 6/8 REDDISH YELLOW7.5 YR 6/8 REDDISH YELLOW

10 YR 6/8 BROWNISH10 YR 6/8 BROWNISHYELLOWYELLOW

5 Y 6/8 OLIVE YELLOW5 Y 6/8 OLIVE YELLOW

5 B 6/1 BLUISH GRAY5 B 6/1 BLUISH GRAY


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Optimum ConditionsOptimum Conditions

Direct Sunlight on color chipsDirect Sunlight on color chips

Light at Right Angles to pagesLight at Right Angles to pages

Soil Moist (required)Soil Moist (required)

If conditions are not optimum, documentIf conditions are not optimum, document

conditions on data sheet.conditions on data sheet.

Whats mostWhats most

important?important?

ChromaChroma is mostis most

important to describeimportant to describe

correctly.correctly.

You must know whetherYou must know whether

the soil isthe soil is chromachroma 2 or2 or

less, or >2.less, or >2.

Hue is probably leastHue is probably leastimportant, unless youimportant, unless you

have ahave a GleyGley huehueChromasof 2 or less


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Depleted Matrices

Depleted MatrixDepleted Matrix

RequiredRequired1144

RequiredRequired224 or 54 or 5

Not requiredNot required 22 66

Not requiredNot required11 55

Redox concentrationsRedox concentrationsChromaChromaValueValue


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Describing Soil ColorDescribing Soil Color

Matrix colorMatrix colorpredominant colorpredominant color

Mottle colorsMottle colorssplotches of contrastingsplotches of contrasting

colorcolor

ll Redoximorphic featuresRedoximorphic features

ll LithochromicLithochromic featuresfeatures

ll Organic matterOrganic matter

ll

OtherOther

Describing mottlesDescribing mottles

ColorColor

AbundanceAbundance

SizeSize

ContrastContrast


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AbundanceAbundance

Few < 2% surface areaFew < 2% surface area

Common 2 to < 20 surfaceCommon 2 to < 20 surface

areaarea

Many >= 20 surface areaMany >= 20 surface area


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SizeSize

Fine < 2 mmFine < 2 mm

Medium 2 to < 5 mmMedium 2 to < 5 mm

Coarse 5 to < 20 mmCoarse 5 to < 20 mm

Very Coarse 20 to < 76 mmVery Coarse 20 to < 76 mm

Extremely Coarse >= 76 mmExtremely Coarse >= 76 mm

Recommend giving actual dimension in mm.

ContrastContrast

FaintFaint

DistinctDistinct

ProminentProminent


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Organic MatterOrganic Matter

Organic Soil MaterialOrganic Soil Material

Mucky modified mineralMucky modified mineral

Organic coatingsOrganic coatings

70% black

50% black

90% black

OrganicCoatings


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Soil material that is saturated with waterSoil material that is saturated with water

for long periods or artificially drained and,for long periods or artificially drained and,

excluding live roots, has an organic carbonexcluding live roots, has an organic carbon

content of: 18 percent or more with 60content of: 18 percent or more with 60

percent or more clay, or 12 percent orpercent or more clay, or 12 percent or

more organic carbon with 0 percent clay.more organic carbon with 0 percent clay.

Soils with an intermediate amount of claySoils with an intermediate amount of clay

have an intermediate amount of organichave an intermediate amount of organiccarbon.carbon.

Types of Organic Soil MaterialTypes of Organic Soil Material MuckMuckHighly decomposedHighly decomposed --


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TextureTexture

The relative proportion of sand, silt andThe relative proportion of sand, silt and

clay.clay.

Estimated in the field by feel.Estimated in the field by feel.

Particle Size ClassificationParticle Size ClassificationClassClass

GravelGravel

SandSand

SiltSilt

ClayClay

Size (mm)Size (mm)

> 2.00> 2.00

0.050.05 -- 2.002.00

0.0020.002 -- 0.050.05

< 0.002< 0.002


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Textural TriangleTextural Triangle


Color of organic soil material may beColor of organic soil material may be

importantimportant

MuckMucksapric materialsapric material

Mucky peatMucky peathemichemic materialmaterial

PeatPeatfibric materialfibric material


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Mucky modified textureMucky modified texture

Mucky modified mineral soil has 0% clayMucky modified mineral soil has 0% clay

and between 5 and 12% organic carbon,and between 5 and 12% organic carbon,

60% clay and between 12 and 18%60% clay and between 12 and 18%

organic carbon, or intermediate amountsorganic carbon, or intermediate amounts

of clay and intermediate amounts ofof clay and intermediate amounts of

organic carbon.organic carbon.

Mucky Modified MineralMucky Modified MineralA USDA soil texture modifier, e.g. muckyA USDA soil texture modifier, e.g. mucky

sand. Mucky modified mineral soil with 0sand. Mucky modified mineral soil with 0

percent clay has between 5 and 12percent clay has between 5 and 12

percent organic carbon. Mucky modifiedpercent organic carbon. Mucky modified

mineral soil with 60 percent clay hasmineral soil with 60 percent clay has

between 11 and 18 percent organicbetween 11 and 18 percent organic

carbon. Soils with an intermediate amountcarbon. Soils with an intermediate amountof clay have intermediate amounts ofof clay have intermediate amounts of

organic carbon.organic carbon.


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Soil HorizonsSoil Horizons

Master Horizons and LayersMaster Horizons and Layers

O horizons or layers:O horizons or layers: Layers dominatedLayers dominated

by organic materialby organic material


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A Horizons:A Horizons: Mineral horizons that have formedMineral horizons that have formed

at the surface or below an O horizon; theyat the surface or below an O horizon; they

exhibit obliteration of all or much of the originalexhibit obliteration of all or much of the original

rock structure and show one of the following:rock structure and show one of the following:

ll an accumulation ofan accumulation of humifiedhumified organic matter intimatelyorganic matter intimately

mixed with the mineral fraction and not dominated bymixed with the mineral fraction and not dominated by

properties characteristic of E or B horizons, orproperties characteristic of E or B horizons, or

ll Properties resulting from cultivation, pasturing, orProperties resulting from cultivation, pasturing, or

similar kind of disturbancesimilar kind of disturbance


E Horizon:E Horizon: Mineral horizons in which the mainMineral horizons in which the main

feature is loss of silicate clay, iron, orfeature is loss of silicate clay, iron, or

aluminum, or some combination of these,aluminum, or some combination of these,

leaving a concentration of sand and sitleaving a concentration of sand and sit

particles. These horizons exhibit obliterationparticles. These horizons exhibit obliteration

of all or much of the organic rock structure.of all or much of the organic rock structure.


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B Horizon:B Horizon: Horizons which have formed belowHorizons which have formed below

an A, E, or O horizon; they are dominated by thean A, E, or O horizon; they are dominated by the

obliteration of all or much of the original rockobliteration of all or much of the original rock

structure and show one of the following:structure and show one of the following:

ll Illuvial concentration of silicate clay, iron, aluminum,Illuvial concentration of silicate clay, iron, aluminum,

humus, carbonates, gypsum, or silica, alone or inhumus, carbonates, gypsum, or silica, alone or in

combination with other characteristics (See keys tocombination with other characteristics (See keys to

soil Taxonomy)soil Taxonomy)


C Horizons or Layers:C Horizons or Layers: Horizons or layers,Horizons or layers,excluding hard bedrock, that are little affectedexcluding hard bedrock, that are little affectedbyby pedogenicpedogenicprocesses and lack theprocesses and lack theproperties of O, A, E, or B horizons. Most areproperties of O, A, E, or B horizons. Most aremineral layers. The material of C layers maymineral layers. The material of C layers maybe either like or unlike the material frombe either like or unlike the material fromwhich thewhich the solumsolumhas presumably formed.has presumably formed.

The C horizon may have been modified, evenThe C horizon may have been modified, evenif there is no evidence ofif there is no evidence of pedogenesispedogenesis..


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R Layers:R Layers: Hard BedrockHard Bedrock

Common Horizon Suffixes forCommon Horizon Suffixes for

Organic HorizonsOrganic Horizons

aa Highly decomposed organic materialHighly decomposed organic material

ee Organic Material of intermediateOrganic Material of intermediate

decompositiondecomposition

ii Slightly decomposed organic materialSlightly decomposed organic material


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Common Hydric Soil HorizonCommon Hydric Soil Horizon

SuffixesSuffixes ggstrongstrong gleyinggleying

wwweak color orweak color or sructuresructure

pptillage or other disturbancetillage or other disturbance

ttaccumulation of silicate claysaccumulation of silicate clays

bbburied genetic horizonburied genetic horizon

Soil HorizonsSoil HorizonsOi -- Organic slightly decomposed

Oe -- Organic moderately decomposed

Oa-- Organic highly decomposed

A-- mineral mixed with organic (humus)

E-- Horizon of maximum eluviation of

silicate clay and Fe and Al oxides, etc

AB or EB-- Transitional to B, more like A or E

BA or BE -- Transitional to A or E, more like B

B-- Most clearly expressed portion of B horizon

C -- Zone of least weathering, accumulation of

Ca and Mg carbonates, cementation, sometimes

high bulk density

R-- Bedrock

BC- Transitional to C, more like B


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A horizon

E horizon

B horizon

C horizon

A horizon

B horizon(unmottled)

B horizon

(unmottled)


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Describing SoilsDescribing Soils

1.1. Look at soil profile and identify topLook at soil profile and identify top

2.2. Break profile into layers (horizons) ofBreak profile into layers (horizons) of

uniform color, mottles, and cracksuniform color, mottles, and cracks

3.3. Describe each layer (horizon):Describe each layer (horizon):

ColorColor

MottlesMottles

DepthsDepths

Type of horizon (A, B, C)Type of horizon (A, B, C)

Matrix Color: 10YR 3/1

Mottle Color: 10YR 4/21 cm diam., 20%


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Horizon DescriptionHorizon Description

A, 0A, 0--20 cm, very dark gray (10YR 3/1) with20 cm, very dark gray (10YR 3/1) with

20%, distinct, dark grayish brown (2.5Y20%, distinct, dark grayish brown (2.5Y

4/2) mottles, 1 cm diameter.4/2) mottles, 1 cm diameter.


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Basic Soils

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