3 Simple DIY Soil Tests

Do You Have Good Soil for Planting?

March 27, 2019
Man With Soil

Success in the garden starts with the soil. It, as much as—and sometimes more than—moisture and sunlight, determines whether plants thrive or die. Here are a few quick and easy ways to test your soil.

Your soil needs to be able to provide nutrients to plants, and allow plants to take up the nutrients in the soil.  Otherwise, your plants just won’t grow well. 

The Peanut Butter Jar Soil Test for Sand, Silt, and Clay

This should take about 1 hour to set up and a full day to conclude. Find an empty straight-sided jar, such as a peanut butter or mason jar, with a lid, and have a ruler handy. Dig down to root level—about 6 inches—in the area that you want to test and remove enough soil to fill the the jar to between one-third and one-half full. Next, fill the jar to the shoulder with water, then set the jar aside to let the soil soak up the water. Put the lid on the jar and shake it hard for about 3 minutes.

  1. Set the jar down and look at your watch. In 1 minute, measure (with the ruler) the amount of sediment that has collected at the bottom. This is the sand in your soil.
  2. Wait 4 minutes more. Measure the sediment again: The difference between the two numbers will be the amount of silt in your soil. 
  3. Take a third measurement in 24 hours. The difference between the second and third number will be the amount of clay in your soil. 

Calculate the percentages of sand, silt, and clay, which should add up to 100 percent. Healthy soil typically consists of 20 percent clay, 40 percent silt, and 40 percent sand.

This simple test can help you to decide what to grow: If your soil is high in sand, it will be well-draining. Silt and clay are hard to get wet, but they stay wet; plants that like “wet feet” would be happy here. Choose your plants accordingly and/or amend the soil:

  • If you have sandy soil, add humus or aged manure, peat moss, or sawdust with some extra nitrogen. Heavy, clay-rich soil can also be added to improve the soil.
  • If you have silty soil, add coarse sand (not beach sand) or gravel and compost, or well-rotted horse manure mixed with fresh straw.
  • If you have clay soil, add coarse sand (not beach sand), compost, and peat moss.

Learn more about soil amendments and preparing the soil for planting.

The Pantry pH Test for Soil Acidity or Alkalinity

  1. Place 2 tablespoons of soil in a bowl and add ½ cup vinegar. If the mixture fizzes, you have alkaline soil.
  2. Place 2 tablespoons of soil in a bowl and moisten it with distilled water. Add ½ cup baking soda. If the mixture fizzes, you have acidic soil.
  • If it does not react to either test, the soil has a neutral pH.
  • A very high or very low soil pH may result in plant nutrient deficiency or toxicity. 
  • A pH value of 7 is neutral; microbial activity is greatest and plant roots absorb/access nutrients best when the pH is in the 5.5 to 7 range. 

Once you figure out your soil pH, you can change or adjust it. Acidic (sour) soil is counteracted by applying finely ground limestone, and alkaline (sweet) soil is treated with ground sulfur.

See a list of Soil pH levels for different plants.

The Earthworm Test to Gauge Organic Matter

The best time to check for earthworms is in the spring when the soil’s temperature has reached 50°F and its surface is moist. Use a shovel to dig up about 1 cubic foot of soil. Put the soil on a piece of cardboard, break it apart, and look for earthworms. Learn more about the wonderful world of earthworms.

If your soil is healthy, you’ll find at least 10 earthworms!

If your soil has fewer than 10 worms, add more organic matter—compost, aged manure, leaf mold. Organic matter improves structure, slowly releases nutrients, and increases beneficial microbial activity.

See more details on how to take a soil test from our Almanac gardeners.


Reader Comments

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Soil Testing

Thank you for the blog, you explained soil testing methods thoroughly. I got my backyard garden's soil tested from Torrent Labs. It was of great help.

Snake worms

We have been taken over by what they call Japanese Snake worms. They are destroying everything by staying in the top of soil. They do not go into earth and live under leaves and mulch. I have picked up over a thousand while removing rotting leaves and mulch. How can we get rid of them. Went to our extension center and they were no help. Except to say they destroy the top layer of soil.

Soil Testing

You can take a soil sample to your local extension service office and, in most cases, they will perform a pH test for free. For best results, call the extension service office for instructions relative to how to take samples and how many to take. More comprehensive testing is usually available for a small fee by sending a sample to the university that sponsors the extension service in your state. The tests results will include a complete nutrient profile, NPK, etc. as well as physical characteristics of the soil (sandy, clay, loam, etc.)

testing for sand, silt, and clay

The peanut butter jar test was helpful until I went to measure the sediment after 24 hours. There was not an appreciable increase in the sediment at the bottom of the jar. Instead the top half of the jar was a grayish,cloudy mixture. According to a source at the U.S. Geological Survey, "Water molecules are strongly attracted to clay mineral surfaces. When a little clay is added to water, a slurry forms because the clay distributes itself evenly throughout the water." It seems then that clay does not settle out of a water solution, at least not in 24 hours time. So I measured to the top of this slurry and subtracted the other two measurements to obtain the amount of clay. Is that how this test should be done? Perhaps a little information about the properties of clay should be included in the DIY instructions for this test.

Pantry PH test

Thank you for publishing this test.
I already know my soil is very clay-y ( a new house built where garages used to be). However I'm not sure what the acid/alkaline levels are...I suspect they would be more acidic than alkaline. So, since the soil testers one can buy in the shop are pretty expensive (for me, I am retired) I will be able to carry out your suggestions easily.
I am hoping to gradually improve the soil, but it is early days yet