Testing Soil Texture – The Mason Jar Test


Knowing the amounts of clay, silt, and sand that make up your garden soil can help you understand how to maximize your garden production [1]. The proportions of sand, clay, and silt have a direct effect on nutrient retention and microbial populations [2]. I’m about to show you a simple test that you can perform, step by step with pictures, so you can determine exactly what kind of soil you have.

To test soil texture using a mason jar, start by filling the jar 1/3 of the way full of well-sifted soil. Add water to almost the top of the jar and some dish soap. Then shake the mixture up. As the soil/water mixture settles over 48-72 hours the sand, silt, and clay will separate forming horizons. Then their proportions can then be determined.

Steps to conduct the ‘jar test’ for soil texture

1 – Gather Materials

Obtain the following materials before starting. You will need a glass jar with straight sides, a ruler, black marker, and granular dish washer detergent. And, dig your soil.

For digging your soil, ensure you take a cross section of at least six inches depth (15 cm). Don’t just scrape the surface, as you want to get a complete picture of your soil.

*Special NOTE – This is a great time to perform a SOIL DRAINAGE test! You can have both tests happen concurrently, thereby learning even more about your garden soil! See our step by step guide to test your soil drainage here!

2 – Sift the soil

Place a kitchen strainer or sieve over a bucket and push the soil through. This will help break up the particles and remove any larger rocks or roots and other organic matter.

I have to tell you that this is a crucial step to obtain a good mixture! The first time I ever performed this step I did not sift the soil. Even after several minutes of shaking the jar I still had solid balls of clay/silt. So, to get accurate results take the time to sift the soil!

3 – Add soil, water, and detergent to jar

Fill the glass jar to approximately 1/3 full with the finely sifted soil. Add 1 tablespoon of granular dishwashing detergent. Then fill the jar with water to almost the top, leaving a gap.

4 – Shake the jar

Secure the lid to the jar tightly. Then shake up the mixture until the mixture becomes uniform and slimey.

Then set the jar on a flat surface to rest

5 – Mark the Sand Layer

After the mixture has set for one minute, mark the side of the jar with a black marker. This represents the sand component.

6 – Mark the silt layer

After the mixture has set for two hours, mark the side of the jar. This represents the silt layer.

7 – Mark the clay layer

After the mixture has set for 2-3 days and the water is clear, mark the final layer. This is the clay layer.

Interestingly enough the soil sample on the right has no identifiable clay layer. Even though it was taken only about 15 feet away from the sample on the left. Also note the difference in sand particle size……

8 – Determine the amounts of sand, silt, and clay.

Use your ruler to determine the total height of soil. But also record the individual heights of each layer.

Then, to calculate the proportions (percentages) of sand, silt, and clay use the formulas below. Additionally, I would like to point out that the ‘total’ height of mixture is the same as the clay layer.

% Sand = (height of sand) / (total height of mixture)

% Silt = [ (height of silt) – (height of sand) ] / (total height of mixture)

% Clay = 1 – %Sand – %Silt

So, in my example from my garden, I had a the following values

LayerHeight
Clay68 mm
Silt63 mm
Sand43 mm

Example Soil Texture Calculation

Applying these formulas would yield the following results

%Sand = 43 mm / 68 mm = 63%

%Silt = (63 – 43) / 68 mm = 20 / 68 = 29%

% Clay = 100% – 63% – 29% = 8%

9 – Determine the soil type using the pyramid from the USDA (Link below).

You can use the USDA soil texture calculator Opens in a new tab. [3] to determine your exact soil classification.

What does Soil Texture mean?

Your soil is made up of 3 inorganic components, sand, silt, and clay. Knowing the proportions of each component can greatly aid you in optimizing your soil for vegetable production or adding amendments.

Any combination of these three elements that falls into the ‘loam’ category is considered a good base for a successful garden. But, now I will speak on the individual components and how they behave individually.

Sand

Sand is the largest particle size for soil components (0.10 to 2.0 mm). Pure sand will drain water and not hold nutrients. Just think of how little plant life you find on a beach! Sandy soil will be prone to drought and hold little in the way of nutrients.

Silt

The next smallest soil particles are considered silt, and are between 0.002-0.05 mm diameter. Silt is generally silica, rock or some other small inorganic particle. Silt will hold nutrients and water quite well, but still drain.

Clay

Clay is the smallest of soil particle sizes, coming in at anything less than 0.002 mm. Clay will compact quite easily and prevent water drainage. On the flip side though, it holds water and nutrients quite well.

Next Steps

Now that you have determined your soil texture, you can address any drainage problems that you may have.

If your soil falls within the “loam” classification you probably do not need to take any action, as long as your soil drains well.

But if you have ‘sandy’ soil, you can add organic matter such as compost or hummus so that it retains water better.

compost and worm castings
Mixture of composted material and worm castings. Nearly 100% broken down.

If you have clay soil, you can also add organic matter like compost as it will break up clay particles and reduce compaction. This will greatly improve the ease in digging your soil as well as drainage.

One of my favorite ways to add organic matter is to apply a heavy mulch of leaves or straw in the fall. Did you know that leaves contain all essential the nutrients your garden needs!

By doing this worms will eat the leaves, and as they travel down into your soil eject worm castings. So, they will aerate your soil and fertilize it at the same time! They get food, and you are now able to grow more food – that is what you call a Win/ Win!

References:

[1] – Colorado State University Cooperative Extension, CMG Fact Sheet S14. Retrieved 23SEP2020

[2] – Hamarashid, Othman, Hussain 2010, Effects of Soil Texture on Chemical Compositions, Microbial Populations and Carbon Mineralization in Soil. Egypt. J. Exp. Biol. (Bot.), 6(1): 59 – 64 (2010). Retrieved 09-23-2020

[3] – USDA soil texture analysis calculator. Retrieved 23SEP2020

Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over six years. I hope to share some of my knowledge with you! Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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