Determining Soil Constituent Percentages
Country: United States
Date: December 2007
How do you determine the percentage of clay, sand, and sit is in soil?
This is difficult to answer because "clay", "sand", and "silt" (sic) are
not chemically defined, nor is there a "test" to specifically define these
various types of soil. There could be some tests that could be done, but
ultimately these would be arbitrarily setting sedimentation rates, color
or some other classification.
The easiest and least expensive for you is probably this: you can get a set
of screens to separate the components, weigh each fraction, and determine
percentage of each fraction. Check a science supply catalog in the
geology/earth science section.
The analysis of percentage of sand, silt, and clay is usually
done mechanically but could be done digitally with an microscopically
derived image. The size order of soil particles is sand (largest),
silt (next largest), and clay (smallest). Sand particles can be
ten times larger than silt particles and hundreds of times larger
than clay particles, so they can be separated by size fairly easily
with a series of sieves. The percentage of each can then be determined
by weight (gravimetric).
David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory
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Update: June 2012