Environmental Engineering Reference
In-Depth Information
4.5.2 Components of Soil Color
The four components that have the most affect on soil color are organic compounds
(usually black or brown), manganese (Mn) oxides (usually black), iron (Fe) oxides
(usually red, orange, or yellow), and the color of the mineral grains (usually clear or
neutral gray). Soil color is determined by matching a moist soil to a chip in the
Munsell
Book of Color. Each chip has a specific hue, value, and chroma,
identified on the printed page facing each page of chips.
4.5.2.1 Hue
Hue is the chromatic composition (color) of light that reaches the eye. Each
Munsell
page is a different hue that is printed on the upper right corner. Most
soils in the Mid-Atlantic Region are on the 10YR (yellow red) page, with redder
colors on pages to the left of 10YR and more yellow and grayer colors on pages to
the right of 10YR. Additional hues are also used to describe soils on the gleyed
pages. These hues include greens, blues, and neutral colors (white, gray, and black).
4.5.2.2 Value
Value is the degree of lightness or darkness of soil color. The value notations are
found on the left margin of each page beside each row. The lower values have
darker color, while higher values have lighter colors. Value is a continuous scale
from 0 to 10. Whenever soil colors do not match a value chip exactly you can round
the value to the nearest chip.
4.5.2.3 Chroma
Chroma is the strength or purity of color. The chroma notations are found on the
bottom margin of each page under each column. The lower chromas have more
neutral (often grayer) color, while highest chromas have the strongest expression
of that particular hue. Technically, chroma has no upper limit to the scale, but
typically the range found in soils is 0-8. Soil colors that do not match a chroma chip
exactly, should be noted as falling between the two color chips. This can be done
by estimating a decimal value (10YR 4/2.2) or by using a + (10YR 4/2+). Some
Field Indicators require chromas of
x.
So knowing whether the soil color meets a chroma or is in between a chroma is
important.
x while others may require a chroma
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