How to Take a Garden Soil Sample
Take 8 to 10 cores about 6 inches deep, mix them into one sample per bed, and mail it to your state lab. Fall is the best time because lime needs 2 to 3 m...
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soil test soil sample fall garden lime soil ph
How to Take a Garden Soil Sample
Take 8 to 10 small cores from each garden area, dig each one about 6 inches deep, mix them in a clean plastic bucket, and send about a pint to a lab. Do it in fall. The report comes back before the spring lab rush, and lime has months to work before planting.
Track your sample date and pH on the Soil Test Desk. It also checks your results against the pH each crop wants.
When to Sample
- Late summer to fall is ideal. Virginia Tech Extension says sampling when the garden season ends gives you time to correct pH and nutrients before spring, and avoids the busy spring period at the lab.
- Sample a couple of months before planting so lime has time to react (Clemson HGIC). Lime should be mixed in at least 2 to 3 months before planting (University of Georgia Extension).
- Wait 6 to 8 weeks after the last lime or fertilizer application (Virginia Tech).
- Skip wet soil. If it is too wet to work, it is too wet to sample. Squeeze a handful. If the ball breaks apart easily, go ahead.
- Sample right away if plants are struggling and you need an answer. Take a second sample from a healthy area for comparison (Purdue Extension).
What You Need
- A clean trowel, spade, or soil probe
- A clean plastic bucket (no rusty or galvanized metal)
- The lab's sample bag and form, usually from your county extension office or your state land-grant university soil lab
- A marker
Find your state extension soil lab in the Get a real lab test list.
Steps
- Divide the garden into areas that differ: vegetable beds, fruit, flower beds, lawn. Sample each area separately (Purdue).
- In each area, walk a zigzag and collect 8 to 10 cores from evenly spaced spots (Clemson, University of Georgia). For a large yard, Purdue suggests 10 to 15. For a narrow border, 4 to 6.
- Brush away mulch and surface debris first. Dig a V-shaped hole 6 inches deep for gardens. Purdue says 6 to 8 inches. Cut a slice about 1/4 inch thick down one side of the hole.
- Put every slice from one area into the bucket.
- Break up clods and mix well.
- Fill the sample bag with about a pint of mixed soil. Let it air dry if it is very wet.
- Label the bag with the area name and fill out the form, including the crops you plan to grow. The lab uses that to set its recommendations.
- Mail or drop it off. Turnaround varies by lab, and fall is usually faster than spring.
Special Cases
| Area | Sampling depth | Cores |
|---|---|---|
| Vegetable and flower beds | 6 to 8 inches | 8 to 10 |
| Trees and shrubs | 6 inches | 6 to 8 spots around the drip line |
| Lawn | 2 to 4 inches | 8 to 10 |
How Often to Test
University of Georgia Extension says vegetable gardens should be tested every 1 to 2 years. Lawns and ornamentals can go 2 to 3 years once fertility is established. Purdue says 3 to 5 years is enough for beds with no problems. Test sooner if you have a specific crop with tight pH needs, such as blueberries.
What Comes Next
Read the report with How to read your soil test results. If it calls for lime, see when and how to add lime in fall. Compare your pH to each crop in the best soil pH for vegetables.