Soil Texture

Soil texture is a term used to describe the different sizes of mineral particles that make up a soil. Another way to look at it is to think about the different textures of clothing that you wear. Your cotton shirt is made of smaller fibers, while a burlap bag is made up of larger fibers. Each type of material feels different to the touch because they are made up of different sized fibers. The same is true of soil, however soil is made up of mineral particles instead of cloth fibers. Soil particles can be classified into 3 main size classes or “separates”: sand (2.00 to 0.05 mm diameter), silt (0.05 to 0.002 mm diameter), and clay (less than 0.002 mm diameter). Most soils are a mixture of sand, silt, and clay. Different names are given to the soil depending on what percentages of sand, silt, and clay the soil is made up of.

Why is soil texture important?

In general, sandy soils are usually not as fertile. Sandy soils have a harder time retaining moisture and nutrients (water and nutrients just run right through it). Crops can grow in sandy soils, but probably would require more water and fertilization. Sandy soils are typically good for building roads and buildings.

The majority of the time, finer textured soils are more fertile and are able to retain moisture and nutrients more efficiently. However, some soils that are really fine textured become too sticky when wet and too hard when dry to grow crops. They also may shrink and swell too dramatically, which isn't very desirable if you want to build a road or building.

References

Brown, R.B. Soil Texture. University of Florida. Available at: http://edis.ifas.ufl.edu/SS169

Singer, M.J. and D.N. Munns. Soils and Introdcution. 1999. Prentice-Hall, Inc. Upper Saddle River, New Jersey.

Soil Texture Experiment

Identifying Texture by Feel (courtesy of Colorado State University, Cooperative Extension consumer horticulture specialist and Colorado Master Gardener coordinator; C. Wilson, Extension horticulture agent, Denver County; and A. Card, Extension horticulture agent, Boulder County. 12/03)

Feel test – Rub some moist soil between your fingers.
• Sand feels gritty.
• Silt feels smooth.
• Clays feel sticky.

Ball squeeze test – Squeeze a moistened ball of soil in your hand.
• Coarse textures (sand or sandy loam) soils break with slight pressure.
• Sandy loams and silt loams stay together but change shape easily.
• Fine textured (clayey or clayey loam) soils resist breaking.

Ribbon test – Squeeze a moistened ball of soil out between your thumb and fingers.
• Sandy soils won’t ribbon.
• Loam, silt, silty clay loam or clay loam soil ribbons less than 1 inch.
• Sandy clay loam, silty clay loam or clay loam ribbons 1 to 2 inches.
• Sandy clay, silty clay, or clay soil ribbons more than 2 inches.
A soil with as little as 20 percent clay may behave as a heavy clayey soil. A soil needs 45 percent to over 60 percent sand to behave as a sandy soil.

Want to learn more?

Colorado State University Extension: Estimating Soil Texture: Sandy, Loamy or Clayey?

Soil Science Education Home Page

University of Florida Extension: Soil Texture