Soil Composition Test

It doesn’t mater what you call it: soil, dirt, earth, or ground; life on this planet is made possible in no small part to the soil beneath our feet. However, not all soil is created equal. Soil can be divided up between three main categories depending on its size. Sand is the largest and coarsest. It typically consists of pieces of rock and hard minerals. Water and air can run more easily between large sand particles than any other soil type. Silt is the medium sized soil and is typically very fine. It is commonly transported along waterways and deposited in lowlands during flooding events. Silt is mostly made up of decomposed organic matter, making it very nutrient rich. Clay has the smallest individual particles of any soil types. It very easily sticks together and has historically been used as a reliable building material. However, as with most things in nature, there are very few cases of absolutes. Most soil you encounter is a mixture of all three types. This mixture is referred to as a loam. Depending on what percent of each soil type your loam is made of, it can be used for different things. For instance, most plants grow best in a nutrient rich sandy loam. It is made up of more sand than other soil types allowing it to have the perfect mix of nutrients, air, and moisture.

What type of soil do you have in your backyard? Well, with the materials listed above, you can figure that out in just a 24-hour period. Let’s see how!

Supplies

· One mason jar, or alt. container

· Access to soil

· Water

· Ruler

· Small hand trowel (optional)

Step 1: Take a Soil Sample

It’s time to get outside! Find a place with some soil you are curious about. Use your hand trowel and scoop some of that soil into your container. You don’t need a lot; only fill it up 1/3 of the way. When finished, smooth over the divot in the ground to limit your disturbance to the area.

Step 2: Add Water and Mix Well

Fill up the rest of the container with water. Then seal and shake until you have a homogeneous solution, or a mixture that is uniform throughout. You have now effectively mixed all of your soil up and need to leave it sitting undisturbed overnight. During this time, it will settle according to particle size, and you will be able to tell exactly what type of soil you have in your sample.

Step 3: Investigate and Analyze Jar

Now that your soil has settled overnight, it is time to see the results of our test. Be very careful not to mix it while you are analyzing or else you will have to allow it to settle again.

Remember, sand particles are the largest soil type and weight the most, so they will have settled to the bottom of the jar. The middle sized silt will be somewhere in the middle of your soil. The smallest and lightest clay will be on top. Above that is your water, however it will not look the same as when you first put it in. This is because it has absorbed the soluble compounds in the decomposing plant matter that is mixed in with your soil sample. Finally, at the very top of the jar you will observe some of that decomposing plant matter, it is in the process of becoming soil, but is not quite there yet and is much lighter, so it floats atop the water.

Using a ruler, measure the height of your settled soil sample. Then measure the height of each individual layer. Divide the height of each layer by the total height of your soil sample and multiply by 100 to find out what percent of your sample is made up each soil type. For example: if your total soil sample is 10 cm high and your sand layer is 3 cm. 3/10 = 0.3 x100 = 30%. Your sample would be 30% sand.

My sample is almost completely uniform when it comes to the soil type and that is a result of where I sampled. I took my soil sample directly underneath a bush on top of a hill. That means that the only new soil can come from decomposing leaves. As a result, it appears my soil is nearly 100% silt. Do you think where you took your soil sample may have impacted the results of your test? What factors do you think played a part?