The Shake Test

So you are interested in growing plants in your soil. You have picked up a packet of seeds and read on the back: This plant prefers a “loamy soil.” You wonder, what does this mean, and how can I tell if my soil is right? This guide will give you a brief introduction to types of soil, and how to tell what soil you area has.

What is soil?

Soil is not easily defined. This amorphous substance that covers the dry land of our planet can be any shade of color and most any texture. Everywhere it is different, and may or may not be able to grow the variety of plant you have selected. In order to determine what type of soil you have, it is important to understand three key types: Clay, Silt, and Sand

Clay, Silt, and Sand

Simply put this distinction is a scale ranging from small particle sizes to large particle sizes. If you grab a piece of your soil, rub it between your fingers, and notice that it feels sticky: your soil is high in clay. This soil has the smallest sized particles present. If in the same test, your soil feels soapy and smooth: it is high in silt, the next largest particle size. Finally, if the soil feels grainy: it is high in sand, the largest particle size. The best soil type for most farming is a mixture of sand and silt with a little clay. This mixture is known as loam.

Soil types by clay, silt and sand composition.

Image via Wikipedia

So why does a good soil prefer all three soil types? Firstly, many plants prefer not to sit in standing water. Sand allows water to pass quickly through the soil in between the large particles. This is referred to as “drainage”. Clay is high in minerals which plants use as food and energy. Silt is a good medium which both allows drainage and contains some nutrients.

So now you know what they types of soil are, and how to interpret what your plant needs. But how can you tell what type of soil you have? This is when an elegant and age-old test comes into play.

The Shake Test

The shake test is basically a jar filled with water and a sample of your soil. You shake it up and then use the visual results to determine your soil’s content.

What you will need:

—  Clear pint jar with a lid

—  Handful of the soil to be sampled

—  Water

  • First grab a heaping fistful of the soil you would like to sample. Dig down a good few inches (6 or so) before you take your sample to avoid just testing the thin rich upper soil layer; after all, you want to know what the bulk of your soil is like, not just the healthiest part.
  • Next take the wad of soil and dump it in the pint jar. Fill it almost to the top with water and screw the cap on tightly. Shake the jar vigorously for at least five whole minutes. This ensures that any clods of soil are separated.
  • Set the jar down in a sunny windowsill (so you can see into it!) and after a minute you will notice the larger sand-sized particles will have settled out of the cloudy water and onto the bottom of the jar. Mark with a tape or pen where this level is.
  • Come back after a half hour and you will now see another horizon line. These smaller particles are the silt component. Put another marker at that lever.
  • After a couple of days, the water will have cleared and the remaining particles will have  settled out. Mark this level to note the amount of clay-sized particles.

At this point you have your results: the size of the layers determine the percentage of sand, silt, and clay in your soil. Either approximate the percentages, or use a ruler to determine the ratios of the different sediment types. If it turns out that your soil is too rich in clay, try this article to learn how to amend clay soil.

Any Questions? Ask below in the comments!