How Soil Testing Can Help You

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Yellowing lower leaves and leaf loss can be symptoms of nutrient deficiency.

Yellowing lower leaves and leaf loss can be symptoms of nutrient deficiency.

Excessive summer rain has removed many nutrients from soils in southeastern NC. Symptoms of nutrient deficiency include stunted growth, yellow or purple leaves, excessive shedding of older leaves, reduced flowering, and poor flavor in vegetables. If you have observed any of these symptoms on plants in your yard soil testing can help you get to the root of the problem and tell you how to fix it.

Simple and Informative!

North Carolina is one of the few states to offer soil testing at no direct cost to its residents most of the year. Samples submitted between April 1 and the end of November are free of charge. A peak season fee of $4 per sample is charged for each sample submitted between December 1 and March 31.

Boxes and forms for sampling are available from any Cooperative Extension 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 form.

Soil samples can be submitted for testing any time of the year. Results are usually ready within a few weeks and are posted online (learn more). Collecting soil samples only takes a few minutes, can help you save money in your lawn, garden and landscape, and can result in healthier plants by telling you which nutrients are already in your soil and which ones you need to add. If nutrients are needed, they can be supplied with either natural or synthetic fertilizers.

Iron chlorosis on hydrangea caused by high soil pH

Iron chlorosis, seen here on hydrangea, can be a symptom of high soil pH.

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 our area range anywhere from 3.5 (very acidic) to 8.0 (basic) or higher. Most plants prefer to grow in soils where the pH is 5.5 to 6.5. Soil testing is the only way to know if your soil is too acidic and if you need to add lime to raise pH. 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 you have soil tested in the past and had trouble understanding the soil test report, there is good news. The N.C. Department of Agriculture recently unveiled a new report format that is much easier to understand. It features bar graphs that show your pH and nutrient levels and provides several alternative fertilizers you can use, in case you cannot find the specific one they recommend. Reports from samples submitted in the past three years are available in the new format from the NCDA PALS website: http://www.ncagr.gov/agronomi/pals/

How to Test Your Soil

To have your soil tested, collect samples from different areas of your yard. You will need to collect three to five random 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 are going to 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.

When complete, your results will be posted online at http://www.ncagr.gov/agronomi/pals/. 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.

Learn More!

Learn more about soil pH, lime, fertilizer, and other soil issues from these recent articles:

More information about soil testing is available online from the N.C. Department of Agriculture’s website at http://www.ncagr.gov/agronomi/sthome.htm.

Use Extension Search to find research based information from Cooperative Extension systems across the U.S.

Visit your local Cooperative Extension office to learn more about gardening and landscape care. Go to https://www.ces.ncsu.edu/local-county-center/ to find your county Extension center or post your questions to be answered online via Extension’s ‘Ask an Expert’ widget.

Contact your local Cooperative Extension office to get expert advice from an Extension Master Gardener Volunteer:

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