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.  Clay, being the smaller size of particles, feels sticky.  It takes 12,000 clay particles lined up to measure one inch.  Silt, being moderate in size, has a smooth or floury texture.   [Table 1 and Figure 1]

Table 1.  Size of Sand, Silt, and Clay

Name	Particle Diameter
Very coarse sand	2.0 to 1.0 millimeters
Coarse sand	1.0 to 0.5 millimeters
Medium sand	0.5 to .25 millimeters
Fine sand	0.25 to 0.10 millimeters
Very fine sand	0.10 to 0.05 millimeters
Silt	0.05 to 0.002 millimeters
Clay	below 0.002 millimeters

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]

Figure 2.  Soil Texture Triangle

Identifying Texture by Feel

Feel test – Rub some moist soil between fingers

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

Ball squeeze test – Squeeze a moistened ball of soil in the 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 thumb and fingers

• Sandy or 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

Note: A soil with as little as 20% clay may behave as a heavy clayey soil.  A soil needs 45% to over 60% sand to behave as a sandy soil.

Soil Texture by Feel

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 jar) ¼ full of soil.
4. Add water until the jar is ¾ full.
5. Add a teaspoon of powdered, 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 with some soils it 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.

    [clay thickness]
    --------------------  =  ___ percent clay  
    [total thickness]

    [silt thickness]
    --------------------  =  ___ percent silt  
    [total thickness]

    [sand thickness]
    --------------------  = ___ percent sand  
    [total thickness]

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

 

 

Additional Information – CMG GardenNotes on Soils, Fertilizers and Soil Amendments:

#211 The Living Soil
#212 Earthworms
#213 Managing Soil Tilth
#214 Estimating Soil Texture
#215 Soil Compaction
#216 Mulching with Wood/Bark Chips, Grass Clippings and Rock
#217 Soil Drainage
#221 Soil Tests
#222 Soil pH
#223 Iron Chlorosis
#224 Saline Soils
#231 Plant Nutrition
#232 Understanding Fertilizers
#233 Calculating Fertilizer Rates
#234 Organic Fertilizers
#241 Soil Amendments
#242 Using Manure
#243 Using Compost
#244 Cover Crops and Green Manure Crops

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