What Will Soil Testing Tell Me About My Soil?
One of the most important things the soil test measures is soil pH, or how acidic or basic your soil is. Soil pH levels in North Carolina range anywhere from 3.5 (very acidic) to 8.0 (basic) or higher. Most ornamental plants, vegetables, fruits, and lawns prefer to grow in soils where the pH is 5.5 to 6.5, though acid loving plants such as azaleas, camellias, gardenias, loropetalum, and blueberries prefer a soil pH between 5.0 and 5.5.
Soil testing is the only way to know if your soil is too acidic, if you need to add lime to raise pH, and if so how much. Many people apply lime unnecessarily, which can raise soil pH too high, resulting in poor plant growth. Soil test results will also tell you which nutrients you need to apply for the type of plants you are growing. If nutrients are needed, they can be supplied with either natural (organic) or synthetic fertilizers.
Soil test results will not determine if there are diseases or herbicide residues in your soil, or if poor drainage or soil compaction are causing plant problems. If you suspect these issues contact your local Cooperative Extension office for advice.
When Should I Sample?
Submit samples for any planting projects you have in mind several weeks before you plan to plant. This will allow plenty of time for you to get the results back and amend the soil before planting.
Soil samples can be submitted for testing any time of the year. Results are usually ready within a few weeks and are posted online. Winter and spring are the lab’s busiest seasons. Samples submitted during these times may take longer to process. Check current processing times here: http://www.ncagr.gov/agronomi/pals/
How Do I Submit Samples?
Boxes and forms for sampling are available from any Cooperative Extension center (find your local center: https://www.ces.ncsu.edu/local-county-center/). Completed samples should be mailed to the N.C. Department of Agriculture’s soil testing lab in Raleigh, whose address can be found on the soil sample box and submission form. Download a submission form here: http://www.ncagr.gov/agronomi/pdffiles/issoil.pdf
What Does It Cost?
Samples submitted between April 1 and the end of November are analyzed free of charge. North Carolina is one of the few states to offer soil testing at no direct cost to its residents most of the year because of funding derived from a statewide fee on commercial fertilizer. A peak season fee of $4 per sample is charged for each sample submitted between December 1 and March 31.
How Do I Collect Samples?
To have your soil tested, collect samples from different areas of your yard. You will need to randomly collect three to five samples from each section of your yard where you are growing something different; for example, 3 to 5 samples from your lawn, 3 to 5 samples from your vegetable garden, etc. Samples should be collected with a stainless steel trowel and need to be taken around 6” deep. For each sample you submit (example – lawn, garden, flower bed), aim to collect a total of about a cup and a half of soil when the 3 to 5 random samples are mixed together. If there are areas in your yard where plants are not growing well be sure to sample them separately to find out if the problem is nutrient or pH related.
For more details on how to collect and submit soil samples, check out this presentation from NCDA (pdf file): http://www.ncagr.gov/agronomi/pdffiles/HomeApr2014.pdf
How Do I Get My Results?
When complete, your results will be posted online at http://www.ncagr.gov/agronomi/pals/.
For help reading the soil test results, see http://www.ncagr.gov/agronomi/pdffiles/usoilHG.pdf or contact your local Extension center. A detailed publication on the soil test report is available here (pdf file): http://www.ncagr.gov/agronomi/pdffiles/ustr.pdf