Soil Testing

• Before applying fertilizer of any sort to your blueberries, send a soil sample to your local University extension. The soil test will return with recommendations specific for your plants and soil conditions. This will help you better utilize available fertilizers and maintain a proper pH for your plants without spending a lot of time guessing about the needs of your bushes. Over-fertilization can be as detrimental to blueberries as under-fertilization.
  
  

Nitrogen

• Nitrogen is a safe nutrient to assume that your blueberry planting will need yearly. Blueberries are heavy feeders and nitrogen levels can be depleted quickly. Apply nitrogen in the form of ammonium sulfate or urea to keep soil pH low. Apply 60 to 80 lbs. per acre of nitrogen from one of these sources each year prior to the beginning of spring growth.
  
  

Potassium and Phosphorus

• It is uncommon for blueberries to require either supplemental potassium or phosphorus, though both are vital to blueberry production. If a soil test demonstrates a need to add phosphorus or potassium, they can be added as a part of a complete fertilizer. Do not use muriate of potash on blueberries, since this can lead to a toxic build-up of chlorine.
  
  

Calcium, Magnesium and Micronutrients

• Calcium, magnesium and iron deficiencies can be problems within established blueberry plantings. Treat calcium deficiencies with finely divided limestone or calcium sulfate, since they have the least effect on soil pH. Treat magnesium deficiencies with magnesium sulfate or magnesium oxide. If your soil is deficient of both calcium and magnesium, use dolomitic limestone. Use ammonium sulfate to lower the pH of the soil if it has micronutrient deficiencies, such as deficiencies of iron.
  
  

Complete Fertilizers

• Blueberry fertilizers are available in some areas of the country. These formulations are usually 16-8-8 and sometimes come with up to 4 percent of added magnesium. This type of fertilizer is very useful for blueberries when it can be obtained. In areas of lower blueberry production, where this fertilizer is not readily available, camellia or azalea fertilizer can be substituted with good results.