Lower soil pH to increase nutrient intake. Alkaline soil can keep certain acid-loving plants from absorbing the nutrients they need to grow well. Blueberries require acidic soil, and so do other plants such as blue hydrangeas, cranberries, and lingonberries. This specially formulated mixture creates the perfect soil conditions for those plants to really grow. Use as directed, ideally prior to planting. One cup of soil acidifier covers one square yard of planted area. For existing plants, sprinkle soil acidifier evenly over root zone and work into soil. Contains sulfur.