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"Soil color is one of the most obvious features of
soil and organic matter has long been known as one of the primary
pigmenting agents in soil," said Skye Willis, lead author of the Iowa
State study that was published in the March-April issue of the Soil
Science Society of America Journal.
Soil field descriptions made in the U.S. are based
upon the Munsell color system – field scientists match soil color to
standardized color chips based upon hue, chroma, and value. Additional
laboratory tests, such as the chroma meter, offer rapid quantification
of soil color. In general, darker soil colors indicate more SOC is
present.
To test the efficiency of color analysis as a
measure of SOC content on different landscapes, scientists collected
soil samples from an agricultural field and an adjacent native prairie
in northeast Iowa. Scientists analyzed the color of soil samples using
three tests:
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Soil cores were split in half and matched to a
color chip in a Munsell Soil Color Book
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The matrix color of soil layers were described
according to Munsell Soil Book
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Soil was ground and analyzed by a chroma meter,
an instrument used to digitally record the color reflectance of soil
sample.
From these three assessments, scientists determined
the soil color (represented by hue, value and chroma) and predicted
the SOC content.
According to Willis, "We found that typical
description colors done by a soil scientist were nearly as effective
in predicting SOC as the more expensive and tedious method of deriving
colors by a chroma meter."
Color analysis is capable of predicting SOC values
more accurately in common land areas (agricultural fields) in
comparison to less common land areas (native prairies). Additional
studies are needed to better predict SOC under native soil conditions.
This rapid SOC measurement will increase the
understanding, prediction, and modeling efficiency of carbon
distribution across fields, watersheds, and larger regions as the
current methods of characterizing SOC are costly and time-consuming.
As an alternative to direct measurements of SOC, soil color can be
used as an efficient predictor of SOC soil contents. |
