Soil Color GES 394 Revised by Mr. Brian Oram

Quick Review

Soil Structure What are the structural types? What are the structural types? Answer: granular, blocky, prismatic, platy, columnar, massive, Single grain, wedge, massive What are the grades of structure ? Answer: Structureless, weak, moderate, strong Is weak subangular blocky a full description of structure? Answer: NO – A full description would be weak medium subangular blocky (1Msbk)

Soil Color Soil color is one property that can be used to describe horizonation and soil morphology. Soil color is one property that can be used to describe horizonation and soil morphology. The change in soil color with depth is directly related to a variety of processes that are occurring in the soil, see Table 1. The change in soil color with depth is directly related to a variety of processes that are occurring in the soil, see Table 1. The soil color does not effect the behavior of the soils, but provides insights into environmental conditions, formation processes, and other influences on the soil. The soil color does not effect the behavior of the soils, but provides insights into environmental conditions, formation processes, and other influences on the soil. Used is used in classifying soils. Used is used in classifying soils.

Range of Soil Color Soil Colors – soils display a wide range of soil color. Soil Colors – soils display a wide range of soil color. Colors can range from reds, yellow, brown, green, blue, gray and black. Colors can range from reds, yellow, brown, green, blue, gray and black. Colors vary in the brightness of the color, tint, and richness. Colors vary in the brightness of the color, tint, and richness. Which one of these colors is GREEN ? Dark greenish gray – 5GY4/1 Greenish Gray – 10GY5/1

Describing Soil Color Munsell Charts are used to provide standard descriptions and names of color. Munsell Chart displays 322 standard color chips. Munsell Charts are used to provide standard descriptions and names of color. Munsell Chart displays 322 standard color chips. The Munsell description is divided into three parts: The Munsell description is divided into three parts: HueHue ValueValue ChromaChroma

Soil Hue Hue refers to the predominant wavelength of Light that is reflected by The soil. The predominant spectral color ! This chart is a 10YR - Hue

Soil Color Wheel- The Range in Soil Hue In NE PA, the most commons hues are 10YR and 7.5YR

Value Value refers to the lightness and darkness of a color in relation to a neutral gray scale. A Value of 0 is black. Value of 10 is absolute white (pure white). Measure of the amount of light that reaches the eye under standard lighting conditions. Gray is the midway point and has a value of

Soil Value

Chroma Chorma refers to the intensity or brightness of the color and has also been described as the purity of the color. It has also been described as the richness of the color. It has also been described as the richness of the color. A Chorma of 0 is a neutral gray and the maximum Chroma is 20, but a value of 20 is never approached, but The Chroma scale on the Munsell Chart starts at 1. 08

Soil Chorma

Describing Soil Color – Three Components 10YR3/6 – dark yellowish brown YR

Describing Soil Color – Three Components Issue: There are 4 colors described as a dark yellowish brown.

Special Cases for Describing Color For Colors that are pure gray, white, and black. There is no chroma and no hue. The letter N (neutral) takes the place of a hue designation, such as N 2.5/ (black). For Colors that are pure gray, white, and black. There is no chroma and no hue. The letter N (neutral) takes the place of a hue designation, such as N 2.5/ (black). When coloring soil – use a moist soil sample. When coloring soil – use a moist soil sample. Describe the soil color in the field. Evaluate the color with the sun at your back. No sunglasses ! Describe the soil color in the field. Evaluate the color with the sun at your back. No sunglasses ! Describe a fresh face and do not crush the sample. Describe the matrix and any “mottled” patterns. Describe a fresh face and do not crush the sample. Describe the matrix and any “mottled” patterns. The matrix color is the dominant soil color – 50% or more of the sample. The matrix color is the dominant soil color – 50% or more of the sample.

What Colors the Soil ? Organic matter darkens the soil and is typically associated with surface layers. Organic matter will mask all other coloring agents. Organic matter darkens the soil and is typically associated with surface layers. Organic matter will mask all other coloring agents. Water Content – Degree of Saturation Controls the rate of nature of the biochemical reactions. Moist soils tend to be darker in color. Primary factor the oxidation state of the system. Water Content – Degree of Saturation Controls the rate of nature of the biochemical reactions. Moist soils tend to be darker in color. Primary factor the oxidation state of the system. Mineral Content Mineral Content Iron (Fe) is the primary coloring agent in the subsoil. The orange brown colors associated with well drained soils are the result of Fe oxide stains coating individual particles in an oxidized state. Manganese (Mn) is common in some soils resulting in a very dark black or purplish black color.

Soil Coloring MaterialChemical CompositionColor ManganeseMn02Purplish Black HematiteFe203Red GeothiteFeOOHYellow Hydrated Ferric OxideFe(OH)3*nH20Red Brown CalciteCaC03Whitish GlauconiteKMg(Fe,Al)(SiO3)6.3H2OGreenish

Black organic coatings Thank you – Dr. David Lindbo (NCSU)

Red: Hematite and Goethite Yellow: Goethite Gray: No coatings Thank you – Dr. David Lindbo (NCSU)

Where is the Color? Think of the soil ped as an M&M. An M&M has a hard outer shell and then a chocolate center. Think of the soil ped as an M&M. An M&M has a hard outer shell and then a chocolate center. Ok – Well the uncoated soil separates (sand, silt, and clay) are gray and the minerals (Fe, Mn, Silicates, Carbonates, and Organics) create the outer shell or coating. Ok – Well the uncoated soil separates (sand, silt, and clay) are gray and the minerals (Fe, Mn, Silicates, Carbonates, and Organics) create the outer shell or coating. Brown Soil Coating Fe Under Reducing Conditions Gray – Low Chroma Soil Iron Leached from Matrix Fe+2 in Matrix, Less Fe+3

Color Patterns-Mottling Matrix color is the dominant color in the soil. Matrix color is the dominant color in the soil. Mottling is spots or blotches of color in the soil that differ from the matrix color. The pattern may relate to the aeration or drainage of the soil. Mottling is spots or blotches of color in the soil that differ from the matrix color. The pattern may relate to the aeration or drainage of the soil. Gleyed colors are low chroma matrix colors with or without mottles. If the soil is gleyed it is likely to be reduced and wet for much of the year. Gleyed colors are low chroma matrix colors with or without mottles. If the soil is gleyed it is likely to be reduced and wet for much of the year. Mottling associated with periods of saturation and anaerobic conditions are known as redoximorphic features. Mottling associated with periods of saturation and anaerobic conditions are known as redoximorphic features. Note the soil moisture condition when describing. Soils that contain reduced iron may appear light in place, but become darker as the reduce iron begins to oxidize. Note the soil moisture condition when describing. Soils that contain reduced iron may appear light in place, but become darker as the reduce iron begins to oxidize.

Describing Soil Color- For a Redoximorphic Feature Describe the Matrix Color – 50% or more of the soil. Describe the Matrix Color – 50% or more of the soil. Describe the color for the Zone of Reduction – This will typically be the zone with a low chroma. Describe the color for the Zone of Reduction – This will typically be the zone with a low chroma. Describe the color and Zone of Accumulation – This will likely be an area with a high chroma. Describe the color and Zone of Accumulation – This will likely be an area with a high chroma. When describing the color, include notation to include the amount of the surface that is represented by the color. This becomes most critical in determining hydric features and in some states siting land-based wastewater disposal systems. Use the following terminology to describe abundance. When describing the color, include notation to include the amount of the surface that is represented by the color. This becomes most critical in determining hydric features and in some states siting land-based wastewater disposal systems. Use the following terminology to describe abundance. < 2% - few 2-20 % - common > 20% - many

Matrix Color Zone of Reduction Zone of Accumulation 5YR5/6 (> 20% many) 5YR4/4 – reddish brown 5YR7/1 (10 % -common ) Note- Any Ideas of the Soil Structure????

Describing Mottled Size Size ClassSymbolCriteria Fine1< 2 mm Medium22 to < 5 mm Coarse35 to < 20 mm V. Coarse420 to < 76 mm Extremely Coarse5> 76 mm

Degree of Contrast This represents the degree of difference between the matrix and the “mottled” pattern. Types of Contrast Faint – difficult to see in place Faint – difficult to see in place Distinct – easy to see in the test pit Distinct – easy to see in the test pit Prominent – easy to see from outside the pit. Prominent – easy to see from outside the pit.

Degree of Contrast

Example Faint Distinct Prominent Chroma Value Thank You Dr. Lindbo

Example Faint Distinct Prominent 10YR 2.5Y 5Y 7.5Y 2.5YR 5YR 7.5YR Thank You Dr. Lindbo

Examples MatrixFeatureContrast 10YR 4/4 10YR 6/3 Faint 10YR 6/4 10YR 4/2 Distinct 10YR 5/6 10YR 4/1 Prominent 10YR 5/4 5YR5/3Distinct

Reduced matrix Does the soil have reduced Iron? Add a,a’-dipyridyl dye – A red color – positive for reduced iron

Quick Review

What is the Soil Color ? 10YR Page YR6/3 – pale brown

Soil Color GES 394 Revised by Mr. Brian Oram