Soil Color

Though it has little impact on a soil’s use or behavior, color is another characteristic which can be used to classify and better understand a soil’s condition. Soil colors are described using a standard Munsell color chart. Three components of color are described:

• Hue – redness or yellowness, given as a number and letter combination (such as 2.5YR for a very yellowish soil or 10R to a very reddish soil)
• Value – lightness or darkness; given as a number, 0 refers to black
• Chroma – intensity or brightness; given as a number, 0 refers to neutral gray

A soil’s color is determined by holding the soil next to the color chips and selecting the chip which best matches the color of the soil.

Soil colors are the result of the organic matter content, the water content, and the presence of oxidized iron and/or manganese. Organic matter attributes a dark or even black color to a soil. Water also darkens soil color; wet soils are generally darker in color than dry soils. For this reason, it is important to indicate whether a soil was wet or dry when the color was determined. The presence of iron oxides in a soil typically gives it a red or reddish-brown color, though organic matter can mask this color. Anaerobic conditions, or conditions with limited oxygen, yield gray or blue shades. Some minerals also produce distinctive colors.

Color is a useful soil characteristic because it can tell us about the hydrologic regime or drainage status of a soil. Bright colors suggest well-drained soils, because under well-drained and aerated soils, soil minerals will become oxidized and display bright shades. Conversely, iron is chemically altered to compounds with grayish shades under prolonged conditions without oxygen, such as being underwater. Wetland soils very often exhibit gray, blue, or gray-green colors.

For more information…

More information on soil colors and the minerals which cause them.