Soil texture plays a crucial role in gardening and agriculture. It determines how well water, air, and nutrients are retained and distributed in the soil, directly impacting plant growth. Whether you’re a seasoned gardener or just starting your garden journey, understanding your soil’s texture is an important and necessary step towards successful cultivation. Fortunately, you don’t need a fancy laboratory to analyze your soil texture; you can do it at home with the Soil Jar Test.

Importance of Soil Texture Knowledge

Soil texture refers to the relative proportions of sand, silt, and clay particles in your soil. Each of these particles has unique properties.

Sand

These large particles create spaces in the soil, allowing for good aeration and drainage. However, sandy soils struggle to retain water and nutrients.

Silt

Silt particles are smaller and can hold more water and nutrients than sand. However, they can compact easily, leading to drainage problems.

Clay

Clay particles are the smallest and have a slow water absorption rate, causing initial run-off issues. Once the clay particles do absorb the water, a new issue arises of poor drainage, resulting in high water retention and compacted soil, This, in turn, suffocates the plant roots.

Loam

The ideal soil texture for gardening is Loam, which is a balanced mixture of sand, silt, and clay. Knowing your soil’s texture helps you make informed decisions about soil amendments, irrigation, and plant selection.

The Soil Jar Test

The soil jar test is a straightforward and cost-effective method to get insights into your soil’s composition. As each particle—sand, silt, and clay—has a different weight and density, this test results in the separation of each particle type into distinct layers that allow you to measure the percentage of each that is present in your soil.

Materials needed

• Quart-sized clear glass mason jar with a lid
• 1 cup soil sample from your garden from 6-8” deep
• 2 cups of water—distilled water works best
• Newspaper
• Non-foaming soap
• Marker

Steps to perform

1. Lay out your newspaper.
2. Spread your soil sample evenly over the newspaper and allow it to completely dry.
3. Finely pulverize the soil with a fork or knife to break up as much of it as possible. 
4. Fill your quart jar with 1 cup of your soil and 2 cups of water.
5. Add 1 tsp of non-foaming soap.
6. Secure your lid tightly.
7. Shake the mixture hard for 10-15 minutes.
8. Place the jar on a flat surface where it will be undisturbed.
9. After 10 minutes, mark the top of the sand layer, which will have settled to the bottom of the jar.
10. After 2 hours, mark the top of the silt layer, which will be the second layer in the jar.
11. Leave the jar undisturbed for at least 24 hours (and possibly up to 3 days) until the water clears.
12. Using the marker, mark on the jar the top of the clay level.

NOTE: A fourth layer may be noticed, which contains any organic matter in your soil. Organic matter is important for your soil’s health and will be covered in a future blog.

Calculating soil texture

1. Measure the total height of the settled soil from the bottom of the jar. 
2. Measure the height of the sand from the bottom of the jar to the line marked on the jar.
3. Measure the height of the silt from the sand line marked on the jar to the silt line marked on the jar. 
4. Divide the height of the sand by the total height of the settled soil.
5. Multiply by 100 for the percentage of sand. 
6. Divide the height of the silt by the total height of the settled soil
7. Multiply by 100 for the percentage of silt. 
8. Deduct the percentage of sand and silt from 100 for the percentage of clay.

Example

 

• The total height of the settled soil = 2.5”
• The height of sand = 1”
• The height of silt = 1”
• % of Sand = 1 / 2.5 * 100 = 40%
• % of Silt = 1 / 2.5 * 100 = 40%
• % of Clay = 100 – 40 – 40 = 20%

Next Steps

Now that you have calculated your soil composition, use the Soil Pyramid to determine your soil texture. 

FIGURE 1 is the Soil Pyramid. Take note of each side. The arrow direction indicates the direction of the line that is to be drawn from the correct percentage for each. 

FIGURE 2 uses the Example Data from the previous section. The percentage of sand is represented by the green line and is drawn from the bottom edge of the pyramid at a left upward angle. The percentage of silt is represented by the purple line and drawn from the right side at a downward left angle. The orange line represents the percentage of clay and is drawn from the left side straight across. 

Where the three lines intersect on FIGURE 2 represents the soil texture of your sample soil. In the example, the soil texture is Loam, which is perfect soil for growing. If your soil is anything other than Loam, you need to amend your soil’s texture by incorporating the appropriate compost mixture,  fully-decomposed manure, or cover cropping.

An Ongoing Process

The soil jar test is a simple yet effective DIY method for identifying your soil’s texture. Armed with this knowledge, you can tailor your gardening practices to optimize your soil and set the stage for healthy, thriving plants.

Remember that soil improvement is an ongoing process. Regularly testing your soil and amending it accordingly will help you create the ideal growing conditions for your plants. In addition, you may want to test different areas of your garden separately, as soil composition can vary greatly—even in the same yard.

So, grab a jar and get to know your soil better. Your garden will thank you for it!