Did you hear about the guy who complained that his coffee tasted like dirt? The waiter reminded the customer that he had insisted his coffee be made with fresh ground.

Whether we call it the ground, dirt or soil, the material in which lawns, gardens and trees grow has much to do with whether plants thrive or languish. Soil is the preferred term, of course, because any soil scientist worth their sandy loam will quickly remind you that “dirt” is something you sweep off the floor.

Esther McGinnis, a North Dakota State University Extension Horticulturist, reminds gardeners of the importance of having our yard and garden soil tested. She says Pinterest gardeners routinely think it is trendy to “improve” their soil by adding lots of organic matter, fertilizers or dubious additives such as Epsom salts.

“But does your garden soil really need all those additions? This is similar to a cook adding salt to the soup without tasting it. You need a baseline before making adjustments. Soil testing is the baseline you need before adding fertilizer, manure or other components.”

Soil tests can reveal nutrient deficiencies or pH imbalances that cause pale, yellowing leaves. Michael Vosburg / Forum Photo Editor
Soil tests can reveal nutrient deficiencies or pH imbalances that cause pale, yellowing leaves. Michael Vosburg / Forum Photo Editor

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The following are reasons why it’s important to have soil tested.

  1. Soil tests are best known for diagnosing nutrient deficiencies. If potassium levels are low, the soil testing lab will recommend potential potassium sources to alleviate the deficiency.
  2. Lesser known is the importance of identifying high nutrient levels. Just like with the salt level in soup, you can add excessive levels of nutrients and amendments if you are not careful.
  3. A lawn and garden soil test will provide information on the amount of organic matter in the soil, which is important for knowing whether the soil would benefit from adding more.
  4. Soil tests measure the pH of the soil, determining its acidity or alkalinity. Soil pH greatly influences plant growth and can be responsible for why some types like Autumn Blaze maple struggle in certain locations.
  5. High concentrations of soluble salts can be detected, with recommendations for remedy.
  6. The information from a soil test can save you money and labor. For example, if your soil has plenty of organic matter, you can skip the laborious process of tilling compost into the soil.
  7. Nationwide, soil testing labs are seeing more gardens that have excessive levels of phosphorus, which can tie up important micronutrients such as iron. In the event of excessive phosphorus levels, a soil testing lab will recommend avoiding amendments high in phosphorus such as manure, 10-10-10 fertilizer and compost.
  8. Soil sampling and analysis gives you chemical and physical information about your soil which can be used to optimize plant growth or assist in solving soil-related problems.
  9. Soil test results taken over time also allow you to follow changes in soil properties. This is useful to track remediation efforts or determine if unfavorable trends are occurring.
  10. If your soil test indicates acceptable levels of nutrients, pH, organic material and soluble salts, you know you’re on the right track.

McGinnis explains that soil testing can be done at any time of year, but is best done before the soil freezes. A fall test allows gardeners to plan their fertilizer strategy before spring planting.

After mixing soil from six spots within the area to be tested, about a pint of soil is submitted to the testing lab. Michael Vosburg / Forum Photo Editor
After mixing soil from six spots within the area to be tested, about a pint of soil is submitted to the testing lab. Michael Vosburg / Forum Photo Editor

To get a representative soil sample, take soil from five or six locations in the garden. Using a shovel or hand trowel, extract a sample that is approximately 6 inches deep. Remove any leaves or organic matter from the top of the soil. Place these samples in a plastic bucket and stir thoroughly to create a composite sample. From this bucket, take at least 1 pint of soil and place it in a baggie.

Before submitting the sample, make sure to provide background information, such as whether the soil sample was taken from a vegetable garden, a flower garden, a lawn or other area. A vegetable garden will receive very different recommendations compared to a perennial flower garden. For example, if you’d like to know the soil analysis of both your lawn and vegetable garden, samples for testing should be submitted separately from each.

North Dakota has two soil testing laboratories. For more information, please contact the following laboratories:

Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at donald.kinzler@ndsu.edu.