Estimating Soil Texture:
Sand, Silt or Clayey?

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Note: For additional information on managing soils refer to CMG GardenNotes #213, Managing Soil Tilth.

Sand, Silt and Clay

Texture refers to the size of the particles that make up the soil.  The terms sand, silt, and clay refer to relative sizes of the soil particles.  Sand, being the larger size of particles, feels gritty.  Silt, being moderate in size, has a smooth or floury texture. Clay, being the smaller size of particles, feels sticky.  [Table 1 and Figure 1]


Table 1.
The Size of Sand, Silt and Clay
Name
Particle Diameter
Clay
below 0.002 millimeters
Silt
0.002 to 0.05 millimeters
Very fine sand
Fine sand
Medium sand
Coarse sand
Very coarse sand
0.05 to 0.10 millimeters
0.10 to 0.25 millimeters
0.25 to 0.5 millimeters
0.5 to 1.0 millimeters
1.0 to 2.0 millimeters
Gravel
2.0 to 75.0 millimeters
Rock
greater than 75.0 millimeters (~2")


comparative size of sand, silt and clay

Figure 1.  Comparative size of sands, silt and clay. If clay was the size of a dot on the page, silt and sands would be a comparative size.


Soil Texture Triangle

The Soil Texture Triangle gives names associated with various combinations of sand, silt and clay.  A coarse-textured or sandy soil is one comprised primarily of medium to coarse size sand particles.  A fine-textured or clayey soil is one dominated by tiny clay particles.  Due to the strong physical properties of clay, a soil with only 20% clay particles behaves as sticky, gummy clayey soil.  The term loam refers to a soil with a combination of sand, silt, and clay sized particles.  For example, a soil with 30% clay, 50% sand, and 20% silt is called a sandy clay loam.  [Figure 2]

Soil Textural Triangle
Figure 3.  Soil Textural Triangle - Based on the triangle, a loamy soil has 40% sand, 20% clay and4-% silt. A sandy loam has 60% sand, 10% clay and 30% silt. [Source: U.S.D.A.]

Identifying Soil Texture by Measurement

  1. Spread soil on a newspaper to dry.  Remove all rocks, trash, roots, etc.  Crush lumps and clods.

  2. Finely pulverize the soil.

  3. Fill a tall, slender jar (like a quart canning jar) 1/4 full of soil.

  4. Add water until the just is 3/4 full

  5. Add a teaspoon of non-foaming dishwasher detergent.

  6. Put on a tight fitting lid and shake hard for 10 to 15 minutes.  This shaking breaks apart the soil aggregates and separates the soil into individual mineral particles.

  7. Set the jar where it will not be disturbed for 2-3 days.

  8. Soil particles will settle out according to size.  After 1 minute, mark on the jar the depth of the sand.

  9. After 2 hours, mark on the jar the depth of the silt.

  10. When the water clears mark on the jar the clay level.  This typically takes 1 to 3 days, but some soils may take weeks.

  11. Measure the thickness of the sand, silt, and clay layers.
  1. Thickness of sand deposit  ____
  2. Thickness of silt deposit  ____
  3. Thickness of clay deposit   ____
  4. Thickness of total deposit  ____

12. Calculate the percentage of sand, silt, and clay.

  1. [clay thickness] / total thickness]  =  ___ percent clay
  2. [silt thickness] / total thickness]  =  ___ percent clay
  3. [sand thickness] / [total thickness]  =  ___ percent sand

13.  Turn to the soil texture triangle and look up the soil texture class.

Soil texture by measurement

Figure 3. Texture by Measurement - Measure the depth of the sand, silt and clay layers.



Identifying Soil Texture by Feel

Feel test – Rub some moist soil between fingers. [Figure 4]

  • Sand feels gritty.
  • Silt feels smooth.
  • Clays feel sticky.

Ball squeeze test – Squeeze a moistened ball of soil in the hand. [Figure 4]

  • Coarse texture soils (sand or loamy sands) break with slight pressure.
  • Medium texture soils (sandy loams and silt loams) stay together but change shape easily.
  • Fine textured soils (clayey or clayey loam) resist breaking.

Ribbon test – Squeeze a moistened ball of soil out between thumb and fingers. [Figure 4]

  • Ribbons less than 1”
  • Feels gritty = coarse texture (sandy) soil
  • Not gritty feeling = medium texture soil high in silt
  • Ribbons 1-2”
  • Feels gritty = medium texture soil
  • Not gritty feeling = fine texture soil
  • Ribbons greater than 2” = fine texture (clayey) soil

Note: A soil with as little as 20% clay will behave as a clayey soil.  A soil needs 45% to over 60% medium to coarse sand to behave as a sandy soil.  In a soil with 20% clay and 80% sand, the soil will behave as a clayey soil.


Figure 4. Soil texture by feel flow chart

soil texture by feel flow chart



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Authors: David Whiting (CSU Extension), Carl Wilson (CSU Extension, retired) and Jean Reeder, Ph.D. (USDA-ARS, retired). Artwork by David Whiting.

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  • Copyright. 2011. Colorado Master Gardener Program, Colorado State University Extension. All Rights Reserved. CMG GardenNotes may be reproduced without change or additions, for nonprofit educational use.

Revised December 2011

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