A Yankee Soil Test

I once had some loam delivered and spread on a section of the lawn and it only grew more crabgrass than I had ever seen. There was plenty of sun, I watered it regularly, I used quality grass seed and seemed to do everything right so why the lack of success. It was the dirt.

Soil is the "physical earth" or "dirt" in our yards and gardens. It is made up of particles of all shapes and sizes and can be heavy on one count and not another. It could be typically heavy in clay, or maybe very sandy.

Loam is soil that has been measured and mixed so one knows the percentage of particles. Ideally the mixture is 40% sand, 40% silt and 20% clay by volume. This mixture is a good growing medium for most plants as the roots are able to penetrate the loam and establish themselves in the growing medium and allowing for better drainage.

Using my home-made soil sample test to find out what was wrong with the loam told me there was too much clay, couldn't tell by looking at it.

You too can make your own test. What you’ll need is a one quart jar with a tight fitting lid (a mayonnaise jar works perfectly if you take off the label so you can see inside), a tape measure or ruler, some water, and a little bit of water softener (such as Downy), and of course some soil.

Collect about six quarts of soil in a bucket. Preferably you’ll dig up a little here and there and only get it from the top 6 inches of soil. Mix this up very well and break up the clods and take out the large sticks, stones and roots. Once you’re confident that you’ve mixed the soil very well, scoop out two level cups of the soil and put in the mayonnaise jar. Discard the rest of the soil.

Then take one teaspoon of the water softener and mix it into one cup of cold water and dump that into the jar. Fill the rest of the jar with water to about an inch from the top and screw the lid on tightly. Then put a good dancing song on Okay Google and shake the jar for about a minute to ensure that all of the soil particles are suspended in the water.

Place the jar on a solid counter top, preferably with back light by a window and set your timer or make a note of what time you set the jar down.

After one minute you will see the particles settling nicely on the bottom, the heaviest being the sand, so it will settle first. When your timer hits about a minute and a half take your ruler and measure the depth of the sand and write this down. It helps to take an indelible marker such as a Sharpie and make a mark on the jar at the sand level.

Once the timer hits two hours take out your ruler and measure the next layer, mark it with the Sharpie and write down the measurement. This will be the silt layer, which is made up of medium-sized particles mixed with tiny particles of sand.

And after the timer hits 24 hours repeat the process with the top layer, it will be the clay layer, the tiniest and lightest particles. You will also see that most of the organic mater will not fall out of suspension in the water and will still be floating after 24 hours. Never mind the organic matter.

The last step in the process is to determine what percentage of each makes up your mix of soil.

Take the total depth of soil in the jar by adding up all three figures you have.
For example I’ll show the results from my soil sample:
sand – 7/8”
silt – 1 3/8”
clay – 1 ¼”
So my total soil depth is 7/8+1 3/8+1 1/4 = 3 ½”.
Then take the depth of each and divide by the total. So my
sand = 7/8 / 3 ½= .25 or 25%
silt = 1 3/8 / 3 ½ = .39 = 39%
clay = 1 ¼ / 3 ½ = .36 = 36%
Just as a check, they should add up to 100%.

Now what does this all mean?

The ideal soil for general gardening purposes will have 35% sand, 45% silt and 20% clay. My soil sample showed that I had too much clay which would explain why the grass didn’t grow correctly.
Clay is a very tiny particle and under a microscope looks like little flat corn flakes. Each particle of clay has a tendency and electronic attraction to other particles of clay, so they stack together and create a hard material that is hard for roots and water and air to penetrate.

The cure for my loam was to spread about a half-inch sand on the top of the soil and about two inches of peat moss on top of that and then rototill in the whole mess, rake it out and replant new grass seeds. It worked, grass is now up and beautiful.


The grass grew very well and is now some of the best lawn on my whole yard.