From:

http://backyardberryplants.com/plantingguides/index.htm

Growing Blueberries Organically:

Annual Fertilization Schedule

Early to mid-spring, usually when the daffodils are in full bloom, we top-dress our blueberries with 1/4 to 1/2 pound Re-Vita Pro fertilizer (5-4-3), depending upon the size and age of the plant (more for older plants).

(any balanced, organic fertilizer will do, and if you use alfalfa meal/pellets, just double the amounts listed for the Re-Vita. Fox Farm sells an organic, acid-loving plant fertilizer that is great for blueberries)

After blossoms have fallen, we begin the liquid feeding of our plants. This is given to them every two weeks through August. It is delivered though drip or hose line, and is applied to the root zone (during fruiting) and foliage (from bloom to green berry, then post-harvest).

Liquid Fertilizer Recipe

For 1 gallon of mixture, add these amounts to 1 gallon of water:

Neptune's Harvest Fish Fertilizer (2-4-1).......2 Tbsp.

Maxicrop or other kelp (liquid)..................� Tbsp.

blackstrap molasses.................................�Tbsp.

Each plant can receive enough to get good saturation, but don't overwater. We usually irrigate the day before applying the liquid fertilizer mix, or apply after a rain shower if it fits the schedule. Usually on mature plants they get a 5 gallon dose, younger plants less. If you planted a blueberry from us last year, it could get 1-2 gallons of this mix, depending upon its size (lowbush less, highbush more).

If you would like to give the plants a foliar feeding of this as well, go ahead and just spray them to dripping with the above solution. However, I would advise using the liquid mix only on the root zone of mature plants with fruits that are ripening (so the berries are not "fishy" tasting). After harvest is done, you can begin foliar treatments. I have found increased production and vigor in our plants the following year when treated with this mix up to the end of August.

In areas of the country with alkaline soils and water, I strongly recommend using the soil-less mix method for planting and growing blueberries. Top dressing the planting area each year with a shovel or two of sphagnum peat moss will help maintain acidity.

The last aspect of a good fertility schedule is mulching, which eventually breaks down to provide nutrients to the plants not found in the purchased fertilizers (in fact, one of the facets of using the fish fertilizer is to add nitrogen to the mulch so microbes can break it down more effectively and release those nutrients for your plants use). Whenever we can, we use shredded oak or maple leaves, and pine needles (these are just the best, so those of you in the south take advantage of the baled pine needles often sold at local nurseries or garden centers). Shredded pine bark will last two to three seasons, but should be dressed if you start to see bare patches in its cover (excellent places for weeds to get in, and they will grow like crazy if they get started). Mulches should be at least 3 inches thick for blueberry plants, and coarse so that water percolates through the mulch easily (that is why the oak leaves need to be shredded or chopped, otherwise they deflect water from the growing area).

That is it, rather simple, yet the old saw "A stitch in time saves nine" is true as ever. Proper care and feeding results in the best production and health for your plants.