Field Notes: Decoding Soil with the Munsell Color Chart

Soil analysis is an essential part of environmental science, providing key insights into land composition, hydrology, and ecological health. In this installment of our “Field Notes” blog series, where we explore essential tools used by Princeton Hydro’s team, we take a deep dive into the Munsell Soil Color Chart—a standardized system that allows professionals to classify and communicate soil characteristics with accuracy. This tool is particularly useful in wetland delineations, where soil color helps determine whether an area meets the criteria for wetland classification.

Understanding Soil Through Color

What if the ground beneath your feet could tell a story? Soil isn’t just dirt; it’s a dynamic, living record of the landscape’s history, composition, and ability to sustain life. One of the most revealing clues in soil analysis is color, which reflects key properties such as drainage, organic matter content, and oxidation levels.

To decode these color variations, scientists rely on the Munsell Soil Color Chart, a standardized system that classifies soil hues based on three components:

• Hue – The dominant color of the soil (e.g., red, yellow, brown, gray).
• Value – The lightness or darkness of the color.
• Chroma – The intensity or saturation of the color.

By matching a soil sample to a color chip in the Munsell book, scientists can precisely classify soil types and infer critical environmental conditions. For example, well-drained soils often appear brown or red due to oxidation, whereas poorly drained soils, such as those found in wetlands, tend to be black, gray, or even blue due to prolonged water saturation.

Applying the Munsell Chart in the Field

One key application of the Munsell Soil Color Chart is in wetland delineation, a process that determines whether a particular area meets the hydrologic, vegetative, and soil criteria for wetland classification. Soil scientists use an auger to extract a sample from the ground, where the first 6 to 12 inches, also known as the upper part, of the soil profile is the most important for determining whether the soils are hydric.

Hydric soils are defined as those that form under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part of the soil. The landscape of the site also plays a crucial role in hydric soil development. Factors such as hydrology, slope, landform, soil materials, and vegetation influence how these conditions emerge. These environmental factors trigger biogeochemical processes that lead to the development of distinct hydric soil indicators, including:

• Redoximorphic features – Oftentimes visible patterns promoted by anaerobiosis, such as the accumulation of organic matter and the reduction, movement, or accumulation of elements including iron and manganese.
• Organic matter content – Darker colors suggest higher organic material accumulation.
• Soil texture and composition – Scientists analyze whether the soil is loam, silt, sand, muck, clay, or a mixture.

Once a scientist identifies a hydric soil, they refer to the Munsell Soil Color Chart to classify its matrix color and any hydric soil indicators present. This classification helps determine whether the area qualifies as a wetland under regulatory guidelines.

Conducting a Soil Profile Analysis with Ivy Babson, PWS

Before conducting a wetland delineation, Princeton Hydro Environmental Scientist Ivy Babson, PWS, first determines which United States Army Corps of Engineers (USACE) Wetland Delineation Region her site is located in—an essential step for ensuring proper classification. For a recent wetland delineation, Ivy identified her site as being within the Northcentral and Northeast Region and conducted pre-delineation research, which revealed that the area was characterized by shallow bedrock and exposed boulders.

Upon arriving at the site, Ivy observed that the wetland had formed within an old basin. The sloped basin floor supported hydrophytic vegetation, including cattails, sedges, and rushes, with visible drainage patterns and hummock-hollow microtopography indicating prolonged wet conditions.

Collecting and Analyzing Soil Samples

Once Ivy selected a suitable location for a soil boring, she used a Dutch auger to extract a soil sample. The first 6 inches of the profile revealed very dark mineral soils with a high amount of decomposed organic material. Using the Munsell Soil Color Chart, she classified the sample as 10YR 2/1—a black, saturated mucky loam.

She also identified strong brown (7.5YR 4/6) redoximorphic features along plant root pore linings, indicating iron reduction due to prolonged saturation:

Before progressing the soil profile further, Ivy noted the groundwater table was very high (about 3 inches) relative to the soil surface:

The next six inches of soil maintained a similar composition before transitioning at nine inches to a gray clay layer (10YR 5/1) with many yellowish-brown (10YR 5/6) redoximorphic features occurring as reduced iron soft masses, another clear indicator of prolonged saturation:

By 15 inches, Ivy hit bedrock, confirming that groundwater was perched above the rock layer, creating the saturated conditions necessary for hydric soil development.

Identifying Hydric Soil Indicators

To determine whether the site met wetland criteria, Ivy referred to the USACE’s Regional Supplement to the Wetland Delineation Manual, which provides region-specific hydric soil indicators. She identified several key indicators in her soil profile:

• Depleted Below Dark Surface (A11) – A depleted or gleyed matrix beginning within 12 inches of the surface, which is located under a dark-colored surface layer.
• Loamy Mucky Mineral (F1) – A mucky loam layer at least 4 inches thick, starting within 6 inches of the surface.
• Depleted Matrix (F3) – A soil layer with 60% or more chroma of 2 or less, beginning within 10 inches of the surface. Redoximorphic concentrations are required in soils with matrix values/chromas of 4/1, 4/2, and 5/2.
• Redox Dark Surface (F6) – A soil layer with a dark matrix with redoximorphic concentrations appearing as iron soft masses or pore linings.

The combination of these four hydric soil indicators proves that the area is a wetland and is subject to conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part of the soil—a conclusion supported by the area’s shallow bedrock, high water table, and saturated soil conditions.

Seeing Soil Through an Artistic Lens

Ivy draws a unique parallel between soil analysis and Vincent van Gogh’s Starry Night, transforming scientific observation into an artistic analogy:

“Looking at the Starry Night painting, my eyes are immediately drawn to the bright yellow stars and white moon against the dark blue night sky. In soil analysis, the dark blue sky represents the matrix of the soil, while the bright stars and moon resemble hydric soil indicators that ‘pop’ out. The streaking cypress tree in the painting? That’s like a redoximorphic concentration of manganese forming around a plant root. Just as these elements make Van Gogh’s painting unique, hydric soil indicators reveal the unique story of the land beneath our feet.”

The Broader Impact of Soil Classification

Beyond wetland delineation, soil classification is a key component of environmental restoration, conservation planning, and land management. The ability to analyze and interpret soil properties helps scientists understand long-term landscape changes, assess soil health, and develop strategies for sustainable land use.

The Munsell Soil Color Chart is particularly valuable in tracking environmental shifts. Subtle variations in soil color can indicate changes in moisture levels, organic content, or chemical composition—factors that influence everything from erosion control to habitat restoration. Soil analysis can reveal how a site has responded to past land use or whether a conservation area is recovering as expected.

By decoding soil characteristics with precision, environmental professionals can make informed decisions that support healthy ecosystems, improve water management, and guide responsible development. The Munsell Soil Color Chart remains a trusted resource in this process, providing a universal language for soil classification and environmental assessment.

Stay tuned for more entries in our “Field Notes” series, where we’ll explore other essential tools used by Princeton Hydro’s team in environmental science, engineering, and ecological restoration.

To learn more about the entire wetland delineation process, check out our “A Day in the Life” blog, where we follow Ivy into the field as she conducts a wetland delineation.

• Environmental Education
• Natural Resource Management
• Wetland Restoration