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Soil ColorSoil Color

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CitationCitation

--Lindbo, D.L., M. H. Stolt, R. Miles, and D. L. Lindbo, D.L., M. H. Stolt, R. Miles, and D. L. Mokma. 2005. 3. Field Description of Mokma. 2005. 3. Field Description of Soils: Color Soils: Color –– Power Point Presentation. Power Point Presentation. inin (D.L. Lindbo and N. E. Deal eds.) Model (D.L. Lindbo and N. E. Deal eds.) Model Decentralized Wastewater Practitioner Decentralized Wastewater Practitioner Curriculum. National Decentralized Water Curriculum. National Decentralized Water Resources Capacity Development Project. Resources Capacity Development Project. North Carolina State University, Raleigh, North Carolina State University, Raleigh, NC.NC.

Soil ColorSoil Color

Why color? Why color? It is the most obvious and easily It is the most obvious and easily determined soil characteristic. Important determined soil characteristic. Important characteristics can be inferred from soil characteristics can be inferred from soil color.color.

Coloring agents in the soilColoring agents in the soil

Organic matter darkens the soil. Organic matter will Organic matter darkens the soil. Organic matter will mask all other coloring agents.mask all other coloring agents.Iron (Fe) is the primary coloring agent in the subsoil. Iron (Fe) is the primary coloring agent in the subsoil. The orange brown colors associated with well drained The orange brown colors associated with well drained soils are the result of Fe oxide stains coating individual soils are the result of Fe oxide stains coating individual particles.particles.Manganese (Mn) is common in some soils resulting in Manganese (Mn) is common in some soils resulting in a very dark black or purplish black color.a very dark black or purplish black color.

Color PatternsColor Patterns

Matrix color is the dominant color in the Matrix color is the dominant color in the soil.soil.Mottling is spots or blotches of color in the Mottling is spots or blotches of color in the soil that differ from the matrix color. soil that differ from the matrix color. Redoximorphic features are mottles that Redoximorphic features are mottles that relate to the aeration or drainage of the relate to the aeration or drainage of the soil.soil.

Elements of soil colorElements of soil color

CoatingsCoatings

Structural grainsStructural grains

Types of CoatingsTypes of Coatings

Organic matter coatingsOrganic matter coatingsFe and/or Mn coatings (Mineralogy)Fe and/or Mn coatings (Mineralogy)

Source of Soil ColorsSource of Soil Colors

RedRed--BrownBrownFe(OH)Fe(OH)33nHnH22OOHydrated Hydrated Ferric OxideFerric Oxide

YellowYellowFeOOHFeOOHGoethiteGoethiteRedRedFeFe22OO33HematiteHematitePurplish BlackPurplish BlackMnOMnO22ManganeseManganese

ColorColorCompositionCompositionMaterialMaterial

Black organic coatingsBlack organic coatings

Gray: No coatingsGray: No coatings

Red: Hematite and Goethite

Yellow: Goethite

Fe-oxide coatings

Why is color important?Why is color important?

1 2 3

What color is this?What color is this?

What color is this?What color is this?

What color is this?What color is this?

What are these colors?What are these colors?

SpectrumSpectrum

HueHue

YR

GYB

P

PR R

PB Y

BG G

HueHue

Hue is a measure of the chromatic Hue is a measure of the chromatic composition of light that reaches the eye, composition of light that reaches the eye, such as: red (R) or yellow (Y). such as: red (R) or yellow (Y). Hues (10R through 5Y) are divided into Hues (10R through 5Y) are divided into four segments of equal visual steps, For four segments of equal visual steps, For example, yellowexample, yellow--red (YR) hue are red (YR) hue are identified as 2.5YR, 5YR, 7.5YR, and identified as 2.5YR, 5YR, 7.5YR, and 10YR 10YR

ValueValue

0 51 2 3 4 6 8 97 10

ValueValueValue indicates the degree of lightness or Value indicates the degree of lightness or darkness of a color relative to gray; darkness of a color relative to gray; value extends from pure black (0/) to pure white value extends from pure black (0/) to pure white (10/); (10/); value is a measure of the amount of light that value is a measure of the amount of light that reaches the eye, gray is perceived as about reaches the eye, gray is perceived as about halfway between black and white and has a halfway between black and white and has a value notation of 5/.value notation of 5/.Lighter colors have values between 5/ and 10/; Lighter colors have values between 5/ and 10/; darker colors are between 5/ to 0/.darker colors are between 5/ to 0/.

ChromaChroma

0 8

ChromaChroma

Chroma is the relative purity or strength of the Chroma is the relative purity or strength of the spectral color. Chroma indicates the degree of spectral color. Chroma indicates the degree of saturation of neutral gray by the spectral color. saturation of neutral gray by the spectral color. chromas extend from /0 for neutral colors to /8 chromas extend from /0 for neutral colors to /8 as the strongest expression of the color;as the strongest expression of the color;Some cards have symbols such as N 6/. These Some cards have symbols such as N 6/. These are totally achromatic (neutral color), and have are totally achromatic (neutral color), and have no hue and no chroma, only a value.no hue and no chroma, only a value.

Hue, Value and ChromaHue, Value and Chroma

Munsell Color SystemMunsell Color System

Hue refers to the dominant wavelength of light Hue refers to the dominant wavelength of light (red, yellow, green, etc.).(red, yellow, green, etc.).Value refers to the lightness and darkness of a Value refers to the lightness and darkness of a color in relation to a neutral gray scale.color in relation to a neutral gray scale.Chroma is the relative purity or strength of the Chroma is the relative purity or strength of the Hue.Hue.NotationNotation

HueHue ValueValue//ChromaChroma10YR10YR 55//66

10YR Page10YR Page

Gley ColorsGley Colors

Refer to colors on the Gley PagesRefer to colors on the Gley Pages10Y, 5GY, 10GY, 10G, 5BG, 5B, 5B, or 10Y, 5GY, 10GY, 10G, 5BG, 5B, 5B, or 5PB with value 4+ and chroma 15PB with value 4+ and chroma 15G with value 4+ and chroma 1 to 25G with value 4+ and chroma 1 to 2N with value 4+N with value 4+5Y with value 4+ and chroma 1 5Y with value 4+ and chroma 1 Gray colors are not always Gley colorsGray colors are not always Gley colors

Gley PagesGley Pages

Recording Soil ColorsRecording Soil Colors

Soil should be moist...This is the most Soil should be moist...This is the most common way soil colors are recorded.common way soil colors are recorded.Always use sunlight. Do not use artificial Always use sunlight. Do not use artificial light. Do not wear sunglasses or tinted light. Do not wear sunglasses or tinted glasses.glasses.Always use a freshly exposed face or ped. Always use a freshly exposed face or ped. Do not crush or rub the soil before getting a Do not crush or rub the soil before getting a color.color.Determine the matrix and all subordinate Determine the matrix and all subordinate colors (mottles).colors (mottles).

SizeSize

<2 mm <2 mm –– finefine22--5 mm 5 mm –– mediummedium55--20 mm 20 mm -- coarsecoarse2020--76 mm 76 mm –– very coarsevery coarse>76 mm >76 mm –– extremely coarseextremely coarseRule of thumb Rule of thumb

your thumb nail is approximately 15 mmyour thumb nail is approximately 15 mmyour pinkie finger nail is approximately 10 mmyour pinkie finger nail is approximately 10 mm

PercentPercent

<2% <2% -- fewfew22--20% 20% -- commoncommon>20% >20% -- manymany

Each 1/4th

of any one square has

the same amount of

black

ContrastContrast

FaintFaintDistinctDistinctProminentProminent

Faint ContrastFaint Contrast

Evident only on close examination.Evident only on close examination.Same hue (page):Same hue (page):

0 to 2 units value change, and0 to 2 units value change, and1 chroma change1 chroma change

Distinct ContrastDistinct Contrast

Readily seen but moderate to the color to Readily seen but moderate to the color to which compared. which compared. Same hue (page):Same hue (page):

2 to 4 units value change and2 to 4 units value change and<4 units chroma change<4 units chroma change

Or same hue (page): Or same hue (page): <4 units value change and<4 units value change and1 to 4 units chroma change1 to 4 units chroma change

Distinct Contrast (cont.)Distinct Contrast (cont.)

Or a hue change of 1 color chart (page):Or a hue change of 1 color chart (page):<2 units value change and<2 units value change and<1 chroma unit change<1 chroma unit change

Prominent ContrastProminent Contrast

Strongly contrasting colors to which they Strongly contrasting colors to which they are compared. are compared. Same hue (page):Same hue (page):

>4 value unit change and >4 value unit change and >4 chroma unit change >4 chroma unit change

Or a hue change of 1 color charts (page):Or a hue change of 1 color charts (page):>2 value unit change and >2 value unit change and >1 chroma unit change >1 chroma unit change

Or a hue change of 2 or more pagesOr a hue change of 2 or more pages

Note that the criteria for Note that the criteria for contrast for use of hydric contrast for use of hydric

soil indicators are soil indicators are different.different.

ExampleExample

Faint

Distinct

Prominent

Chroma

Val

ue7

5

432

1987654321

6

ExampleExample

Faint

Distinct

Prominent

10YR

2.5Y

5Y

7.5Y

2.5YR

5YR

7.5YR

ContrastContrast

PP

DD

ChromaChromaValueValueHueHue

>0>0oror>0>02+ page2+ page>1>1oror>2>21 page1 page>4>4oror>4>4samesameProminentProminent<1<1andand<2 <2 1 page1 page

>1 to <4>1 to <4andand<4<4samesameoror

<4<4andand>2 to <4>2 to <4samesameDistinctDistinct<1<1andand0 to <20 to <2samesameFFFaintFaint

Difference in Color Between Difference in Color Between Matrix and MottleMatrix and Mottle

CodeCodeContrast Contrast ClassClass

Example: Soil PedExample: Soil Ped

Matrix – 10YR 4/4Coating – 10YR 5/6Lining – 5YR 5/8Depletion –10YR 4/1Depletion –2.5Y 4/3

Example Example

DistinctDistinct2.5Y 4/32.5Y 4/310YR 4/410YR 4/4

DistinctDistinct10YR 4/110YR 4/110YR 4/410YR 4/4

ProminentProminent5YR 5/85YR 5/810YR 4/410YR 4/4

DistinctDistinct10YR 5/610YR 5/610YR 4/410YR 4/4

ContrastContrastFeatureFeatureMatrixMatrix

MatrixFeature

Feature

Matrix

Feature

Matrix

Feature 2

Feature 1

Matrix

Feature 2

Matrix

Feature 1

Feature 2

Feature 1

Matrix