Blueberries require a lower pH than many other fruit and vegetable crops. Before planting blueberries, test the soil to determine the pH level, as well as amounts of nitrogen, phosphorus, potassium and organic matter present. More information can be found in the Soil Testing secion of this article, Site Selection for Blueberry Production.
Blueberries require a soil pH of 4.0 to 5.3 for best growth. The primary material recommended for lowering soil pH is finely ground wettable sulfur. Because sulfur reacts slowly and must be converted by soil bacteria, the change in soil pH is brought about slowly; therefore, sulfur should be added to the soil and mixed thoroughly several months to a year prior to planting.
If the soil pH is in the range of 5.4 to 6.0, sulfur can be applied six months before planting to lower the pH. Sulfur also can be applied after planting to the soil surface but not mixed with the soil. Rates of up to 7/10 pound per 100 square feet can be used yearly, if needed. If the initial soil pH is above 6.0, growing blueberries will be difficult unless massive amounts of peat moss or milled pine bark are mixed with the soil. Use 1 pound (2.5 cups) per 100 square feet on sandy soils to lower pH by 1 unit (for instance, from 6.0 to 5.0). Apply 2 pounds per 100 square feet for the same amount of pH lowering on heavier soils containing silt, clay or more than 2 percent organic matter. Try to achieve a pH of around 4.8; too much reduction can be detrimental to bush growth.
Gu, Mengmeng and Keith Crouse. Soil pH and Fertilizers. Retrieved 16 March 2010.