Soil Texture Calculation
Soils are composed of mineral content, organic matter, air and water. The mineral content is often defined by particle size, and is commonly classed into three categories based on particle size as shown.
Sand - 2.00 mm - 0.05 mm
Silt - 0.05 mm – 0.002 mm
Clay - < 0.002 mm
Soil texture is an important characteristic of soil and determines, in part, the ability to hold or drain water, the amount of air available to critters and roots, and the movement of nutrients in the soil. To measure the texture, begin with a shovel and a clean 1 litre mason jar.
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Dig a hole at least 8" or the depth of the shovel. This ensures you will not collect a sample for additives or mulch
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Fill a mason jar to 1/3 with soil. Remove any rocks.
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Fill the jar with clean water and shake for 3 or 4 minutes.
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Set the jar down somewhere where it will not be disturbed for 24 hours.
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In 10 minutes, measure the depth of the first layer, which will be sand. It will have sunk to the bottom. You should see a clear boundary where sand has settled out from the rest of the soil
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In 4 hours, measure the depth of the second layer, which will be silt. It will be cloudy, but do your best to estimate.
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In 24 hours, measure the remainder of the soil, from the top of the silt layer to the bottom of the water. Do your best.
Collection and Measurement
Calculation of Percentage:
The following chart is an example of this calculation. Enter heights of sand, silt and clay on a piece of paper. Then, add them up to determine the total amount of soil. Once you have the total (shown highlighted) use the calculation shown to determine the percentages
The next step is to chart your percentages on the Soil Triangle. Shown right, we have entered the example percentages on the Soil Triangle, and it was determined that the soil is Sandy Loam
Sandy loam is generally a very good garden soil. It drains well while still retaining useful moisture and nutrients, and its loose texture provides good aeration for roots.
Download a copy of the Soil Texture Triangle here and good luck with the calculations.
