Q. Should I use sulfur to acidify the soil this fall before planting blueberries next spring?—Courtney Bernard, North Charleston, South Carolina
A. Blueberries grow optimally in acidic soils with pH between 4.5 and 5.5. Start by having soil samples analyzed to determine existing soil pH where you want to plant, says Geoff Zehnder, Ph.D., coordinator of Clemson University's Integrated Pest Management and Sustainable Agriculture Programs and director of the Clemson Student Organic Farm. If the pH is much above 5.0, says Zehnder, then you might consider adding an amendment to lower the pH. "Some organic amendments like pine needles and peat moss can gradually lower soil pH over several years, as can some organic fertilizers like cottonseed meal. The addition of sulfur can lower pH more quickly, but it can still take 1 to 2 years to see an effect."
So it's definitely a good idea to get started well ahead of the intended planting time. The amount of sulfur to use will depend on the soil's initial pH and its texture, and ranges from 1 to 7 pounds per 100 square feet. Ask the testing service that will analyze your soil samples—the state agricultural extension or a private lab—for recommendations, based on your specific soil conditions, for growing blueberries. Mix the recommended amount of sulfur into the upper 6 inches of the soil in the area where you will plant the blueberries.
Originally published in Organic Gardening Magazine, Oct/Nov 2013