Cheap and Easy Mason Jar Soil Composition Test

What’s the Point?

The mason jar soil test will give a great snap shot as to what the soil texture in your gardening space is. Soil texture is important for drainage, retaining of nutrients, and root health (especially root vegetable growth). Once soil texture is determined, there are a lot of simple amendments that can effectively balance the soil if needed.

Simply simple

This test is so simple to complete that I sent my kids out to prepare it with minimal verbal instructions. Now, if you know my kids, them following verbal instructions at all can be a nightmare. So hopefully that sells you on the simplicity of this test preparation. I can’t say the same for the analysis, but that is what I am here for.

Supplies

• Mason jar and lid (or another glass jar)
• Water
• Soil from growing area
• Ruler (preferable with the metric system because it makes your math easier)
• Calculator or the ability to do long division
• Soil texture chart (shown below)

Preparing the Sample

1. Fill the jar halfway with soil.
2. Fill the jar the rest of the way with water.
3. Shake the jar vigorously for about 30 seconds until well mixed.
4. Let the jar sit for 24 hours until the different soil types have settled separately.

Analyzing the Sample

Soil types settle in layers due to their weight. Sand is on the bottom, then silt, and the lightest, clay, is on the top. In order to obtain the soil type with the chart, the percentage of each type of soil in the sample will need to be determined. To do this is where the dreaded math comes (and if you ask my kids, I evented math to ruin their lives).  At this point, measure the total soil height. Then measure the total height of each soil type and record these numbers.

Soil Math 101

This math will be based on my results, but can easily be completed using any measurements. As seen below, each individual soil texture measurement will be divided by the total soil height. This number will then be multiplied by 100 to find the percentage. So with my sand measurement being 2.5 cm and my total soil height being 4.8 cm I would divide 2.5 by 4.8 which equals 0.52. Next, I will multiply 0.52 by 100 which tells me that my soil is 52% sand.

What do these numbers mean?

These percentages can now be applied to the soil texture chart. This is done by starting with sand and following the corresponding diagonal left facing line. Note where this line goes. Next, follow the horizontal line that corresponds with the clay percentage and note where it passes or goes near the sand line. Finally, go to the diagonal right facing line for the silt and find which area it intersects with the other to lines on the chart. Below you will find a video charting my soil type. This area represents the type of soil that is in your garden.

What to do with this information?

Ideal soil type is loam. That being said, great plants can still be grown in soil that isn’t loam and poor soil can generally be amended easily. Using the soil texture chart to decide what type or soil you have too much of or too little add and true some of the following suggestions.

Too much clay

• Till soil, and add any combination of the following:
  • Organic Matter
  • Sand
  • Saw dust
  • Manure
  • Lawn clippings
  • Worm casings
  • Planting a cover crop to aerate soil and add organic matter

Too much sand

• Add any combination of the following:
  • Organic Matter
  • Green manure
  • Lawn clippings
  • Humus
  • Or Peat moss

Too much silt

• Add (surprise, surprise) organic matter, and:
  • Decomposed wood shavings
  • Mulch
  • Manure

Is this type of soil test sufficient?

Overall, this is an excellent, easy, fast, and inexpensive way to get a pretty good idea of what kind of soil you’re starting with or to evaluate after adding amendments. Many tests can also be completed over a large area for the same price. This test can be performed at state labs, such as University of Idaho Lab, but can get pricy in a hurry. This wouldn’t be my recommendation unless you need a very precise type soil for specialty crops or if you’re continuing to have issues after amending soil. If you would like to test for nutrient content, check out my soil test guide.