Many plants thrive in acidic soil--any soil with a pH lower than 7.0. According to the Improve Your Garden Soil website, maintaining a 6.0 to 6.9 pH provides the best environment for plants that require acidic soil. Use pH kits to regularly test your soil. Research the specific soil requirements for the vegetation you want to plant, and increase the soil acidity as needed.
Test the moist soil with a pH testing kit.
Calculate the difference in the current pH level and the desired pH level. For example, if the tested soil pH is 8 and the desired pH is 6, the difference is 2.
Measure the gardening area. Calculate the square footage of the area.
Apply sulfur powder to the top of the soil area to reduce the pH in one-point increments. Use 10 pounds of sulfur powder per 1,000 square feet for sandy soil. Use an additional 5 pounds per 1,000 square feet for medium-grade soil and 10 additional pounds for heavy clay soils.
Rake the area with a garden rake to work the powder into the topsoil.
Lightly mist the area with water, if the soil is dry.
Retest the soil pH in 2 weeks. Repeat process until obtaining the desired soil acidity level.