Most plants grow optimally in soil with a pH between 6.0 (slightly acidic) to 7.5 (slightly basic). If you decide to plant an acid-loving plant or the pH of your soil is simply too high to provide the right environment for plants, you may want to lower the pH of your soil. Doing so can also relieve compaction and poor drainage. Knowledge of how to amend your soil so that the pH decreases will help make a more hospitable home for your plants.
Perform a soil test to determine just where the pH of your soil lies. You can do this by using an at-home soil test kit or by bringing a sample to your local extension office.
Place down a 2-inch layer of sphagnum peat moss on top of the alkaline soil. Dig 8 to 12 inches into the soil with a spade, mixing the peat moss as you go. Sphagnum peat moss is an acidic amendment that will both improve drainage and lower the pH of the soil.
Lay down 6 to 10 pounds of elemental sulfur per 1000 square feet. Mix it into the top 8 to 12 inches of soil. The sulfur will slowly oxidize in the soil to form sulfuric acid.
Test the soil again after three months. If you are happy with the result, stop amending your soil. If you want to lower the pH even more, apply the elemental sulfur to the soil again.