SMALL SPACE GARDENING: Start this year’s garden with a soil test

by Melinda Myers

Growing a beautiful landscape starts with the soil under your feet. The best place to start building a healthy soil foundation is with a soil test. The results will tell you what type and how much, if any, fertilizer is needed for the plants you are growing. Using the right type and amount of fertilizer is also good for your budget and the environment.

Test the soil when starting a new garden or one that is struggling. Since soil and fertilization practices vary greatly, collect and submit separate samples for each garden bed or landscape area to be tested. Repeat every four or five years to check on your garden maintenance.

You can take a soil test anytime the ground is not frozen and you have not recently fertilized. Early spring and fall are good times since you can make needed changes when preparing your garden.

Contact your local Extension service for details on submitting a sample. If they don’t have a soil testing lab, they will likely recommend a state certified lab that tests home lawn and garden soils, or you can search the internet for a certified lab near you.

Taking a soil test sample is simple. Use a clean trowel and bucket to gather a soil sample.

Slide away any mulch or debris on the soil surface. Use a trowel and remove a slice of soil that is four to six inches deep and right where the plant roots grow.

Take several samples throughout the garden you want to test. Collect samples from each edge and several throughout the middle of the bed. Mix them together and place about a cup of the soil in a plastic bag or the one provided by the lab. Be sure to complete and include the submission form. This includes a place to list the types of plants that will be grown in the area being sampled. The lab uses this and test results to make the fertilization recommendations. Send the sample and form together to the soil testing lab.

Allow several weeks for the test to be completed and the results to be returned. Most basic soil tests report the amount of phosphorus and potassium in the soil. Phosphorus promotes flowering, fruiting, and root development. Potassium promotes drought tolerance, disease resistance and hardiness. Many soils are high to excessive in these plant nutrients. You cannot remove the excess but should avoid adding to the problem. Soil test reports can help you do just that.

Most labs do not measure the amount of nitrogen in the soil since the levels change quickly and are not easy to test accurately. Instead, they make nitrogen recommendations based on the plants you are or will grow in the area being tested.

Soil pH is also measured in most soil tests. Acidic soils with pH below neutral (7.0) are often referred to as sour, while alkaline soils with a pH above 7.0 are called sweet.  Soil pH influences which nutrients in the soil are available for the plants to absorb and utilize for growth. Blueberries, azaleas, and red maples are examples of acid-loving plants. Clematis, crabapples and spireas are a few of the alkaline tolerant plants.

Always use soil test results when trying to change the pH. Lime is used to sweeten soils while sulfur is often used to lower pH. Using too much or the wrong amendment can negatively impact the health and productivity of your garden. Undoing misapplications can take years to correct. Growing plants suited to the soil pH may be the best solution for those with acceptable, although not ideal, soil pH.

Include soil testing when planning new gardens or helping those that are struggling. Understanding your soil can help you create a strong foundation important to the health, longevity and beauty of your gardens and landscapes.

Melinda Myers has written more than 20 gardening books, including The Midwest Gardener’s Handbook, 2nd Edition and Small Space Gardening. She hosts The Great Courses “How to Grow Anything” DVD series and the nationally-syndicated Melinda’s Garden Moment TV & radio program. Myers is a columnist and contributing editor for Birds & Blooms magazine and was commissioned by Summit for her expertise to write this article. Her website is www.MelindaMyers.com.