Jar Soil Test

OSU Extension, Agricultural Literacy Coordinator

When you think about texture, you probably think about words like ‘smooth’, ‘rough’, ‘fuzzy’ or ‘scratchy’. Texture is the physical feeling of something when you touch it. Soils have textures too, although it’s not usually the first thing people think of when they talk about soil. Soil is made up of organic matter like dead plant roots and leaves, but the part of soil that gives it texture is the mineral part that is made from different sizes of rocks that have been worn down. There are three sizes of these worn-down rock particles: sand, silt, and clay. While these are all small particles to us, in the soil they are really different! Sand is the largest particle size and has a really gritty, rough texture. Silt is the next largest particle size and has a soft, smooth texture (sort of like baby powder). Clay is the smallest particle size and has a smooth, sticky texture (think of modeling clay). When these soil particles are present in different amounts, they give soil a distinct texture that, with the help of an ordinary jar, will let you know how much of what particle size is in your soil. Knowing the texture of your soil is helpful because it can tell you if you will need to water more often (sandy soil), if you will need to be careful to not do anything when the soil is wet so it doesn’t get compacted (clayey soil), or if your soil is somewhere in between (loamy soil).

To do a jar test at home, you’ll need a few basic items:

• A quart sized jar with a lid
• Soil (enough to fill the jar half full)
• Calgon water softener (optional, will still work without it)

Fill your jar half full with soil (remove any rocks) and wet the soil enough to make it muddy and then tap the jar to settle the soil. Then mark the soil level with a marker or white-out. If you have Calgon water softener, add a teaspoon to the jar. Fill the jar to the top with water and put the lid on tightly. Shake the jar really well so that the soil is well mixed with the water. Put the jar down on a table or counter and leave it for 40 seconds then mark the soil level on the jar. This is the sand portion of your soil. Leave the jar undisturbed for six hours then mark the soil level on the jar. The distance between your sand mark and the new mark is the silt portion of your soil. The distance between your very first mark and your silt mark is the clay portion of your soil.

You can calculate the percent sand, silt, and clay by measuring the depth of the soil from the bottom of the jar to your first mark (sand) in inches, then the first mark (sand) up to the second mark (silt), and the distance from the second mark (silt) to the starting mark (the one you made before shaking it up). The percent sand is the depth of the sand layer divided by the total depth then multiplied by 1.19 (this converts from percent volume to percent weight). The percent silt is the depth of the silt layer divided by the total depth then multiplied by 0.87. The percent clay is 100 minus the percent sand plus the percent silt then multiplied by 0.94.

Find your soil on the table below!

Source: soils4teachers.org

photos courtesy of Tracy Wilson

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