Learn what your soil is made of with our Soil Jar Science experiment!
- 1 pint or quart glass jar with a tight fitting lid
- Liquid dish soap
- Shovel or trowel
- Head outside and dig a hole. Aim to go at least 6-8 inches deep.
- Now dig out some more soil and add it to your jar. Fill the jar about halfway.
- Now add clean clear water, not quite to the top, a little more than ¾ full.
- Add 1 tsp of liquid dish soap. The dish soap acts as a surfactant which keeps the soil particles separate.
- Tighten the lid and shake the jar for several minutes.
- Set the jar aside where it won’t get bumped or disturbed, at least 3-4 hours or overnight. (Now’s a good time to go back outside and fill in that hole you dug!)
Since you’ll have some time while you wait for your soil to settle, get to know the different components of soil: sand, clay, and silt.
- Has the largest particles
- Particles are round which leaves larger spaces between particles
- Water drains quickly from sandy soils (because of those larger spaces between particles)
- Nutrients also drain more quickly
- Has the smallest particles
- Particles are flat. Their flatness and tininess means they fit tightly together
- Water drains slowly from clay
- Is somewhere in the middle
- Particles are larger than clay but smaller than sand
When these three types of soil are mixed together in amounts that are ideal for growing plants, it’s called loam. In general, “loamy” soils are about 40% sand, 40% silt, and 20% clay. Let’s see how “loamy” our soil sample is by looking at how the soil settled in the jar we collected and shook up:
Bottom Layer = Sand: this is where the larger, heavier particles settle
Middle Layer = Silt
Top Layer = Clay
What if there’s stuff floating at the top of the water? That’s any organic matter that was in the soil sample, bits of leaves for example.
Does the color reveal anything about the soil? Sure does. Lighter colors usually contain less organic matter, darker colors more.
How do people use this soil test? Some gardeners test the soil of their garden beds or a place they are thinking about planting a new garden. Finding out what your soil is made up of can tell you how close you are to that ideal loamy soil for gardening.