When and with what do I fertilize blueberries?

Soil fertility should be adjusted prior to planting blueberries, based on the recommendation from a soil test. Once the plants are installed, side-dress at bloom and six weeks later with 0.1 pound of ammonium sulfate per plant each time. Ammonium sulfate also helps maintain an acidic pH. In subsequent years, use the same timing and increase the amount of fertilizer by 0.1 pound each year until you are applying 0.3 pound of ammonium sulfate per bush per application. Be sure to apply the fertilizer completely around each plant because little lateral transfer of nutrients occurs from one side of the bush to the other. Sulfur-coated urea can be used as a nutrient source; however, it is not as acidic as ammonium sulfate and, when used, requires the soil pH be checked more often. On sites with heavier soils and where the pH is more difficult to maintain, plants can be fertilized with Osmocote Plus 15-9-12 at a rate of 2 ounces per plant per month from March 1 through Aug. 1. If you use wood chips or sawdust for mulching, plants may need additional nitrogen at a rate of 0.1 pound of ammonium sulfate per plant for the first few years.