Testing Garden Soil For Clay Content

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Testing for garden soil clay content is something every gardener wants to try. The concern is that if the clay in your garden soil is too high you may have issues with drainage and compaction. This gardening in Canada article is going to look at how to test for clay content in garden soil.

If you are new to this blog my name is Ashley and I am a soil scientist. I am located in a Canadian Zone 3 and a USDA Zone 4. I write articles, make YouTube videos, Instagram & Facebook posts all designed for Canadians and Cold Climate gardeners using science-based methods. If you are looking for anything specific be sure to let me know in the comments down below.

Clay garden soil is not a bad thing in small doses. If you have a loam garden soil that consists of clay, sand and silt in relatively equal amounts you have black gold. To understand how much clay soil your garden soil contains I encourage you to go check out my soil texture testing article.

Garden Soil Ribbon Texture Test

  • Collect your sample from each horizon you identified in the previous tests.
  • Add enough water to make a playdough consistency.
  • make a ribbon using your palm and index
  • Use the image below to determine what soil type you have and document.
Garden soil textural triangle
Garden soil textural triangle

If you are noticing that the garden soil is heavy clay you may want to check out my article on amending clay soils.

You can also check out the following videos on ammedning clay soils to help you out:

Where does clay soil come from?

Clay soil is found in areas that have a large depression. If you look at the landscape surrounding clay soil you will notice that it is in a low spot. This is because clay soils are found in areas that used to be ancient lake beds. These ancient lake beds have very fine sediment that is deposited through gravity and settling over time. The initial sediments are a result of rapidly flowing rivers entering a lake bed. These rivers were turbulent and therefore they would break away at the bedrock and rock in their pathway. This fine inorganic material was eventually turned into the powder mixture we now call clay.

North America is covered by the old lake bed. Many of which were here during the last ice age. You can look at maps to see your city or town to see where they were located. And to identify if you were in an ancient lake bed area. The other case would be a recent lake that has either dried up or has receded. If you were living in an area of a receded lakebed then this will also cause high clay soils.

If you’re noticing that your garden or landmass is splotched with clay you may be in a glacial till area. Having a combination of sandy soil and clay soil is not uncommon in a glacial till landscape. Glacial till is simply a way to describe a landscape that has been torn up by glaciers. This tearing up of the soil surface and bedrock has resulted in areas of rock deposits, sand deposits, and even clay. These landscapes also typically have a wide range of both chemical and physical attributes.

How to identify problem clay soil?

Being able to identify clay soil is important when determining how to reclaim it. True clay soil is often rare. The more common clay version of soil we see is a sandy loam or a loam of some sort. If you have loam soil then you are less likely to experience the intense negative side effects of clay soil.  If you are unsure how to check your soil texture at home then be sure to check out my work booklet that goes through exactly how to test your soil.

Signs You Have Clay Soil As Seen In Crops.

The first sign that you may have heavy clay soil or clay soil that needs reclamation is through crop performance. Something you may notice in a crop grown in heavy clay soil is a lack of performance. This may show up in a few different ways.

The first sign of this is a root rot or chlorosis scenario. Chlorosis is the development of yellow leaf margins and green leaf veins. This is a sign that your soil pH is not adequate for plant growth. This change in pH is commonly caused by a lack of drainage which is commonly found in clay soils. The other sign you have a heavy clay soil would be root rot.

If a plant dies off and you are able to simply pluck it from the ground with very few roots attached. This may be a sign that you have suffered from root rot. Root rot is another sign of poor draining soil in the garden. Poor draining soil is a sign of heavy clay particles due to lack of drainage and aeration.

You will need to use some common sense here. If you are dealing with a large amount of rainfall, overwatering or some form of flooding when the symptoms arise. This may not mean the soil is heavy clay but rather the weather conditions have caused the issue.

Water Pooling On The Soil Surface Is A Sign Of Clay Soil

The other sign that you may have heavy clay soil is based on pooling. If you have pooled in your garden after a heavy rainfall that persists for hours this is a sign you may have clay soil. Because clay particles are so close together we run into issues of water pooling. The other way to test this water retention level is through a percolation test. I also outlined how to perform this test in your garden in my soil testing book.

Colours In Clay Soil

The colour of your soil or lack of colour in your soil is also another indication of clay material. Because Clay is able to retain water and has a poor ability for drainage, things such as oxidation of iron in the soil profile will cause a rusted look. That rusted appearance is a sign that the soil has a heavy clay content and is unable to drain in an acceptable time frame.

Surface Soil Erosion In Clay Soils

If there are signs of erosion on the surface this is another sign that you may have clay soil. Because the water is not able to penetrate the soil profile quickly if the angle of the landscape is at all downhill then you may have signs of erosion. These signs of erosion would include Gully’s or rills. These typically look like rivers when the water is flowing and similar to ditches when the water dries out.

Testing for garden soil clay content is something every gardener wants to try. The concern is that if the clay in your garden soil is too high you may have issues with drainage and compaction. This gardening in Canada article looked at how to test for clay content in garden soil. Feel free to share your results with me over on Instagram.