Estimating Soil Texture:
Sand, Silt or Clayey?
Outline
- Sand, silt, and clay
- Soil texture triangle
- Identifying soil texture by measurement
- Identifying soil texture by feel
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
Fine sand
Medium sand
Coarse sand
Very coarse sand
0.10 to 0.25 millimeters
0.25 to 0.5 millimeters
0.5 to 1.0 millimeters
1.0 to 2.0 millimeters
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]
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.D.S.A]
Identifying Soil Texture by Measurement
- Spread soil on a newspaper to dry. Remove all rocks, trash, roots, etc. Crush lumps and clods.
- Finely pulverize the soil.
- Fill a tall, slender jar (like a quart canning jar) 1/4 full of soil.
- Add water until the just is 3/4 full
- Add a teaspoon of non-foaming dishwasher detergent.
- 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.
- Set the jar where it will not be disturbed for 2-3 days.
- Soil particles will settle out according to size. After 1 minute, mark on the jar the depth of the sand.
- After 2 hours, mark on the jar the depth of the silt.
- When the water clears mark on the jar the clay level. This typically takes 1 to 3 days, but some soils may take weeks.
- Measure the thickness of the sand, silt, and clay layers.
- Thickness of sand deposit ____
- Thickness of silt deposit ____
- Thickness of clay deposit ____
- Thickness of total deposit ____
12. Calculate the percentage of sand, silt, and clay.
- [clay thickness] / total thickness] = ___ percent clay
- [silt thickness] / total thickness] = ___ percent clay
- [sand hickness] / [total thickness] = ___ percent sand
13. Turn to the soil texture triangle and look up the soil texture class.
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
Additional Information
CMG GardensNotes on fertilizers
- Calculating Fertilizer Application Rates, #233
- Iron Chlorosis, #223
- Organic Fertilizers, #234
- Plant Nutrition, #231
- Soil Tests, #221
- Understanding Fertilizers, #232
CMG GardenNotes on soil amendments
- Cover Crops and Green Manure Crops, #244
- Making Compost, #246
- Soil Amendments, #241
- Using Compost in the Home Garden, #243
- Using Manure in the Home Garden, #242
CMG GardenNotes on soil management
- Asking Effective Questions about Soils, #251
- Earthworms, #218
- Estimating Soil Texture, #214
- Introduction to Soils, #211
- Iron Chlorosis, #223
- Managing Soil Tilth, #213
- Mulches for the Vegetable Garden, #715
- Mulching with Wood/Bark Chips, Grass Clippings and Rock, #245
- Soil Compaction, #215
- Soil Drainage, #219
- Soil pH, #222
- Soil Tests, #221
- The Living Soil, #212
- References and Review Questions: Soils, Fertilizers and Soil Amendments, #210
- Homework: Soil, Fertilizers, and Soil Amendments, #253
- Worksheet: Soil Texture and Structure Lab, #252
- CMG GardenNotes are available online at www.cmg.colostate.edu
- Colorado Master Gardener/Colorado Gardener Certificate Training is made possible by a grant from the Colorado Garden Show, Inc.
- Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating
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No endorsements of products mentioned is intended nor is criticism implies of products not mentioned.- Copyright. 2010. 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