You’ve probably already started thinking about what to plant in your garden this spring, but is a soil test part of your plan? Soil testing is a simple process that takes the guesswork out of gardening so you can ensure your plants have what they need to thrive.
Why do I need a soil test?
Incorrect fertilizer applications can lead to water quality issues, wasted resources, and stressed plants. On the flip side, using the results of a soil test to apply the correct type and amount of fertilizer will lead to healthier plants and minimize unintended consequences.
How can I apply the soil test results?
The basic test will provide two important statistics: soil pH and macronutrient content. Those macronutrients are phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). The pH of your soil determines which of those nutrients can be absorbed by the roots of your plants.
Looking at your soil’s pH and nutrient content will tell you whether you need to improve soil fertility and guide you in plant selection. The nutrient content of soil is depleted over time as your plants use those resources, and the soil test will give you a definitive guide for replenishing them. Compare the pH of your soil to the pH needs of your plants to determine whether that requires adjustment.
Additionally, a soil test will tell which plants will thrive in that space and which will not (“right plant, right place!”). For example, many turfgrasses, flowers, vegetables, and fruits want a slightly acidic soil with a pH of 6.1 to 6.9, while azaleas need a pH between 4.5 and 6. If your soil is alkaline, it will be easier to plant something that will thrive in those conditions instead of attempting to lower the soil’s pH (although that can be done).
How can I get one, and what is the process?
Stop by our office (OSU Madison County Extension) to pick up a soil test kit for $12. This kit contains instructions, a bag for your soil sample, and a pre-addressed packet for mailing.
To collect your soil sample, use a soil probe (you may borrow this from our office) or simply a garden spade/knife/hand trowel. The required depth of your soil sample depends on where you’re taking it from:
- New turfgrass seeding or sodding: 6-7 inches
- Established turfgrass: 4-5 inches
- Flower bed or vegetable garden: 6-8 inches
- Trees and shrubs: 6-10 inches
Because these areas have different requirements (and will have different test results), you should submit a separate soil sample for each location. Use your chosen tool to dig up a slice of soil and place it in a clean plastic bucket, removing any organic matter (living or previously living plant material). Repeat this 10-15 times throughout the chosen location. When finished, mix the soil in your bucket until it is thoroughly blended.
After ensuring the soil is completely dry, fill the white bag in your soil test kit with the composite soil sample you collected. Label the soil test bag and fill out the included form. If you are ordering multiple soil tests, double check that the ID on your soil sample matches what you write on your form (i.e. a test for your lawn should be labeled “lawn” to not confuse it with your “garden” soil test).
Finally, place your soil sample and form in the pre-addressed mailer and seal it. You may either mail it yourself or bring the package back to the Extension office to have it mailed (for an additional fee). Once the lab receives your sample, they will send your soil test results and fertilizer recommendations within two weeks by email and/or mail.
If you have any questions while preparing your soil test or interpreting the results, don’t hesitate to ask for help. You can reach Amanda Douridas, Agriculture and Natural Resources Extension Educator, at douridas.9@osu.edu or 740-852-0975.
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Article written by Natasha Atlas, Extension Educators Coordinator with OSU Extension Madison County. Have a gardening question? Send it to us by emailing whitman.179@osu.edu.