Montana Soils

The Color Palette

Soils are important for the beauty their many colors add to our landscape. Most of us overlook this natural beauty because we see it every day. Often these colors blend with vegetation, sky, water, and other natural features. Over the centuries, humans have used soil colors to serve as pigments in bricks, pottery, and art work. These artifacts from the past give us an idea of how early people lived and worked.

Montana has over 1,300 different soil types. Each soil has its own unique characteristics. This map does not depict the true colors of these soils. Rather, it shows a general trend of lighter colored top soils in the driest parts of the east with the darkest top soils in the rich, moister grassland regions. Forested mountainous areas are midway between. The reason for the darkest top soils is that they have more organic matter built up over thousands of years in the high root-density grassland communities. More vegetation with high root densities result in organic matter to build rich topsoil and stain the soil a darker color.

Generalities About Montana Soil Colors

• Even if an area is light in color overall, darker soils can be found. A darker color means more organic matter is present as a result of additional moisture and plant growth.
• Similarly, light soils can be found in areas that are generally darker. In this case, a light soil often shows where soil development is thinner due to slope or as a result of erosion. Also, lighter soil colors can be found in subsoil.
• The colors of subsoil and, to a lesser degree, top soil are based on parent material.

Definitions

• Organic matter consists of plant and animal material that has decomposed to various degrees.
• Parent material is the bedrock or mineral that soil forms from.
• Top soil is the top layer of soil that is most affected by vegetation.

How Soils Are Grouped

Red, pale red, black, brown, yellow, yellowish-red, grayish-brown are all colors of soil. However, describing soils in these terms is not very exact! So, just like paint stores, there is a book of soil colors used worldwide called the Munsell Soil Color Charts. The color information is based on the soil classification system used by soil scientists for describing soils. Soil samples are compared to the colors in the charts and given a specific value. Agronomists, biologists, archeologists, geologists, zoologists, and other scientists also use these charts to document colors.

Soils in Montana have been put into general groups with dominant soil characteristics. Iron provides the greatest variety of pigments, colors range from yellow to brown to red. Soils with high amounts of organic matter decompose into black humus—in grasslands the dark color permeates the layers of soil. Soils with high amounts of lime are almost white. Soils with a green tinge have higher amounts of copper.

Black, Black/Brown – Soil that has high organic matter content and nutrients for plants. These are deep soils formed mainly in materials transported by water, ice, or gravity. This includes glacial deposits and soil deposited by rivers.
Gold – Soil from certain sandstones.
Taupe – Clayey soils with lower organic matter content. Soils formed mainly in residual materials from ancient sea beds.
Red – Soil with a high iron content.
Cream – Soil with high amounts of lime or formed in wind-blown silty material.

For More Information

For instructions on collecting local soils, processing them, and making paint for your own art work, see the Natural Resources Conservation Service (NRCS) publication, “Painting With Soil.”

Learn more about soils and find educational materials for other natural resource topics on the NRCS Conservation Education webpage.

You can also purchase prepared soil samples from the Montana Chapter of the Soil and Water Conservation Society (SWCS). To order the soil, submit the Soil Painting Kit form on the Montana SWCS Chapter website. Educational materials for soils will be added to the Chapter website as they are updated. Check back for new tools.

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Montana Soils: The Color Palette (347 KB)

Last Modified: 06/29/2007