Soil Texture Analysis “The Jar Test”

Soil is a medium comprised of soil particles, organic matter, water, air, and living organisms, all of which are important to the soil’s overall health and the plants that grow in it. There are three primary soil particles: sand, silt, and clay. The relative percentages of these components present make up the soil’s texture. Texture is related to soil porosity and directly impacts soil and plant health by affecting moisture and air holding capacity in soils.

The ideal soil texture is a mix of sand, silt, and clay particles, known as a loam. However, in most cases, the particles will not be balanced, and the soil must be amended by adding organic amendments. To evaluate soil texture, use a simple jar test to determine the percentages of sand, silt, and clay. Once the percentages are calculated, the soil textural triangle can be used to determine the soil type.

Soil Texture Analysis “The Jar Test” Procedure

Materials:

Straight-edged, clear jar
Permanent marker
Ruler
Watch or stopwatch
Mesh sieve or old colander

Procedure:

1)Using a mesh sieve or old colander, sift the soil to remove any debris, rocks, and large organic matter (leaves, sticks, roots, etc.).
2) Fill the jar ⅓ full of the soil to be tested

A jar filled a ⅓ of the way with soil.
Drew Jeffers, ©2018, Clemson Extension

3) Fill the remainder of the jar with clean water, but leave some space at the top.

Fill the remainder of the jar with water, leaving space at the top.
Drew Jeffers, ©2018, Clemson Extension

4) Cap the jar and shake vigorously until the soil turns into a uniform slurry.
5) Set on a level surface and time for one minute.
6) Place a mark on the outside of the jar, showing the coarse sand layer settled at the bottom of the jar.

Jar showing the coarse sand layer settled at the bottom of the jar.
Drew Jeffers, ©2018, Clemson Extension

7) Leave the jar in a level spot for 2 hours.
8) Mark the top of the next settled layer with the permanent marker. This is the silt layer.

Jar showing the silt layer.
Drew Jeffers, ©2018, Clemson Extension

9) Leave the jar on a level spot for 48 hours.
10) Mark the top of the next settled layer with the permanent marker. This clay layer has settled on top of the silt layer.

Jar showing the clay layer.
Drew Jeffers, ©2018, Clemson Extension

11) Using a ruler, measure and record the height of each layer and the total height of all three layers. Use the soil texture analysis worksheet below to record the results.

Using a ruler, measure and record the height of each layer and the total height of all three layers.
Drew Jeffers, ©2018, Clemson Extension

12) Use the soil texture triangle to estimate the soil type for the site.
a) The clay percentages are listed on the triangle’s left side. Lines corresponding to clay percentages extend from the percentages reading left to right (see red line).
b) The silt percentage is on the right side, with lines extending downwardly, diagonally from right to left (see green line).
c) The sand percentage is on the right side, with lines extending upwardly, diagonally from right to left (see blue line).
13)Track the lines with the percentages measured and find the spot on the triangle where all three lines intersect. The region where these lines intersect indicates the soil type present. The example shown represents a loam soil texture.

Most soils in South Carolina will require some form of organic amendments. Adding organic matter to clay and sandy soil can help with:

Nutrient holding capacity
Improved drainage
Reducing compaction

For more information on amending soils, see HGIC 1655, Soil Conditioning – Establishing a Successful Gardening Foundation.