Blueberry bushes have abundant fruit by their sixth year, but years of fertilization and care are needed while they are still young. Since flavorful and healthy blueberries are only produced in acidic soil, nitrogen is the most important element used to fertilize growing blueberry bushes. Ammonium sulfate or urea can be used to add nitrogen to the soil.
Fertilizing New Plants
You will need to fertilize your newly planted blueberry bushes when they are four weeks old. A twenty percent nitrogen fertilizer mix or ammonium sulfate elements promote growth and ensure soil acidity. Application is best done in early spring, before the foliage starts to appear. Make sure that the soil and plant is dry, and do not apply fertilizer directly to the plant stem. Protect the young blueberry bush stem by staying six inches away from the stems as you spread the fertilizer. Direct application burns and damages the young blueberry plant. Instead, spread an even layer of the twenty percent nitrogen fertilizer directly to the soil. Use about an ounce of the fertilizer per plant. If you use ammonium sulfate, only use two or two and a half ounces for every twenty-five feet of plantings. Follow the same procedure in early spring for the first two years.
By the time your blueberry bushes are well established they are hardier and require higher concentrations of fertilizer. After their second year, spread two to three ounces of ammonium sulfate for every twenty-five feet of blueberry bushes when they start producing flowers. A month to a month and half after the first application, apply the same amount to the plantings again. If you are attending to individual plants, you can apply five ounces of a nitrogen rich fertilizer to the soil around each plant. A special blueberry fertilizer is the 16-8-8 combination, which refers to the amount of nitrogen, potassium and calcium it contains. If that is not available, buy a 10-10-10 fertilizer. Apply about five ounces of fertilizer per plant. Blueberry bushes that have become chlorotic need an application of ferrous sulfate or iron chelate once each year. Chlorotic plants do not have enough chlorophyll and the leaves are pale or white.
Elements to Avoid
There are some fertilizing elements that are harmful to blueberry bushes. Although nitrogen plays the greatest role in producing healthy blueberry bushes and fruit, never apply nitrogen in nitrate form. Nitrates may kill or severely damage the plant. Other elements to avoid are chlorides, found in muriate of potash. Instead of muriate potash or chlorides, look for fertilizers that contain potassium sulfate. Prepared fertilizers containing nitrogen (sometimes aluminum sulfate or urea), potassium and calcium are good choices for growing blueberry bushes.