Cultivating a beautiful landscape starts with the ground beneath 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 fertilizer, if any, 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. Because soil and fertilization practices vary widely, collect and submit separate samples for each garden bed or landscape area to be tested. Repeat this every four or five years to review your garden maintenance.
You can always do a soil test if the soil is not frozen and you have not recently fertilized. Early spring and fall are good times as you can make the necessary changes as you prepare 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 in your area.
Taking a soil sample is easy. Use a clean trowel and bucket to collect a soil sample.
Push mulch or debris away from the soil surface. Use a trowel and remove a pat of soil four to six inches deep and right where the plant roots are growing.
Take several samples from the garden you want to test. Collect samples from each edge and several in the middle of the bed. Mix them together and place about a cup of soil in a plastic bag or the one provided by the lab. Be sure to fill out and attach the submission form. This includes a place to list the plant species grown in the area to be sampled. The lab uses these and test results to make fertilization recommendations. Send the sample and form together to the soil testing lab.
Wait a few weeks for the test to complete and the results to be sent back. 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 rich in these plant nutrients. You cannot remove the excess, but you should avoid making the problem worse. Soil surveys can help you with that.
Most labs do not measure the amount of nitrogen in the soil because levels change quickly and are not easy to test accurately. Instead, they provide nitrogen recommendations based on the crops you grow or will grow in the area tested.
Most soil tests also measure soil pH. Acidic soils with a pH below neutral (7.0) are often referred to as acidic, while alkaline soils with a pH above 7.0 are referred to as sweet. Soil pH affects what nutrients in the soil are available for plants to absorb and use for growth. Blueberries, azaleas, and red maples are examples of acid-loving plants. Clematis, crab apple and spireas are some of the alkali tolerant plants.
Always use soil test results when attempting to change pH. Lime is used to sweeten soil, while sulfur is often used to lower pH. Using too much or the wrong supplement can negatively impact your garden’s health and productivity. Undoing misapplications can take years to correct. Growing crops that are soil pH adapted may be the best solution for those with acceptable, if not ideal, soil pH.
Include soil testing when planning new gardens or helping those who are struggling. By understanding your soil, you can create a strong foundation essential 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 is also an editor for Birds & Blooms magazine. Her website is melindamyers.com.