Click on triangle to see larger version. When finished click on "back" to return to Chapter 2.
Texture by Feel is another way to determine the soil's
textural class name.
Click on triangle to see larger version. When finished click on
"back" to return to Chapter 2.
The textural triangle is used to determine the "Textural Class Name" of the soil. If you know the percent of sand, or silt, or clay (any 2 of 3) you can determine the textural class name from the triangle. You follow along the lines for the respective particle size. For clay the lines go from right to left, for sand they go from lower left to upper right, and for silt from lower right to upper left.
It does not take very much clay in a sandy soil to have a big influence on the soil properties; for example, a loamy sand could have 80 % sand, 5 % clay, and 15 % silt. However, at the other end, the "clay" soils will still have 25 % sand, 30 % silt, and 45 % clay. Clay textures greater than 80% clay are not very common, so clay soils are generally between 45-65 %. Clay's influence on texture will occur even with only a small percentage of clay. This is because of the very high activity of the clay particle.
Loam is often a confusing term. Loam is a soil texture with about equal activity of sand, silt, and clay. Even though there is 28% clay or less, the clay is readily apparent when the soil is felt in the hand. A loam feels like equal parts of sand, silt and clay, but of course it does not have equal parts of each separate. A soil of equal percentage of sand, silt and clay would be a clay loam.
For the soil scientist in the field every day is a situation where they do not have access to a laboratory to use the hydrometer method. Therefore, the simpler method of determining soil texture by the "feel method." is used.
In order to determine the soil texture by feel, the soil must be moistened. Add
a small amount of water until the soil is "putty - like."
You want to be able to move the soil about between your thumb and forefinger.
In doing this manipulation of the moist soil, you are feeling if the soil is
gritty, sticky, or smooth, which are the "feel" characteristics for
sand, clay and silt, respectively.
After you have worked the soil, you try to extrude the soil between your thumb and forefinger to make a "ribbon"; the longer the ribbon, the more the clay in the sample.
Soils with a lot of sand will fall apart, while those with more clay will eventually be able to be worked into a very good ribbon which is > 2 inches long. Silty soils feel very smooth, and a loam feels smooth, yet slightly sticky, and has just a little feel of grit. Eventually, after much practice, you will be able to get pretty good at it.
Soil judgers depend on feel texturing to write their soil profile
descriptions. The photo below shows a soil judger working hard at texturing.
For more information about soil judging go to Soil
Judging at UM.
Before you practice texture by feel in the laboratory, Go To Feel Texture Slidesto see slides of "Ribbons" of Soil
Texturing takes practice, spend some time practicing in the laboratory on the known and unknown samples.
To next chapter for- Soil Texture: Chapter 3- Texture Profiles
Review Chapter 1 - Mechanical Analysis
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