Test the soil pH level with a pH testing kit 1 to 2 years before planting strawberries. Purchase a soil testing kit from a local gardening store or arrange for testing with your local county extension office. The soil must remain around a pH level of 5.8 to 6.5 for strawberries.
Lime raises the pH level and sulfur lowers it. Fertilizers high in ammonium also acidify soils, but they often add other nutrients. Follow the directions on the package or the recommendations from the extension office to determine how much to add to the soil. Each type additive requires specific dosages according to your soil type.
Check the pH level after six months to 1 year. Amend the soil again if necessary to ensure that it remains slightly acid for the strawberries.