Living Columns & Blogs

Great gardens start with a soil test

This is my periodic, obligatory soil test article. Don’t let your initial knee jerk reaction prevent you from reading!

This topic isn’t as “sexy” as organic gardening, pollinator plants or even cherry trees here in Macon. But, if you stay with me for a few moments, this topic — soil testing — can make all of those things grow better.

Collecting a soil sample and understanding the report from the University of Georgia laboratory are two of the foundations of a successful garden.

Plants need essential nutrients, much like people need them. If they are not supplied in adequate amounts, we can anticipate problems. Plant nutrients are divided into two groups. The macronutrients (nitrogen, potassium, calcium, magnesium, phosphorus and sulfur) are required in larger quantities, while the micronutrients (chlorine, iron, boron, manganese, zinc, copper, molybdenum and nickel) are required in smaller quantities. A soil test report will contain fertilizer recommendations, as well as a pH analysis.

Why does pH matter? The soil pH must be in the correct range — for many plants, that’s between 6.2 and 7.2 — for plant roots to effectively absorb these macro and micro nutrients from the soil. Typically, a pH level around 7 is considered neutral. Lower pH levels, like those in battery acid, lemon juice and vinegar, are more acidic; while higher pH levels, like those found in ammonia and milk of magnesia, are more alkaline.

This is important to know because different plants require different pH levels in order for their roots to absorb nutrients. You can add a truckload of fertilizer, but if your pH level is not in the correct range, it will be useless to the plants.

In Georgia, our soils tend to be more acidic. The addition of limestone raises the pH level to an appropriate range prior to planting. Lime takes several months to become soluble and move down into the soil profile. Dolomitic lime, which contains both calcium and magnesium, is recommended for homeowners. Although it is initially slow to change the pH level of the soil, it will maintain the pH level longer.

Routine soil testing is easy and affordable — especially since testing is only recommended every few years. While soil testing can be done throughout the year, autumn is the recommended time. This will allow the amendments, particularly lime, to work down into the soil profile before spring, when new growth begins.

When collecting a sample, gather soil from eight to 10 random areas around your yard. Dig down 4-8 inches deep where roots grow. Mix a scoop-full from each of the different areas together in a plastic bucket. From this mixture, take one cup of soil to your local extension office. Fees vary per county, but typically fall between $6 and $8.

What a great tool for landscapers and gardeners! For more information on soil testing procedures, contact your local extension office.


2017 Bibb County Master Gardener Extension Volunteer program: Classes will be held each Thursday from Feb. 2-April 27. Prior plant experience is not necessary; a heart for community service is! Applications are due Nov. 30. Contact Kathy at 478-751-6338 or for more information.

Contact county Extension agent Karol Kelly at