BSmith:

You are right in that 21-0-0 can burn the roots. I mix one tablespoon in 3 gal water for soil application. Applying a 1/4 cup in a quart of water will burn the roots at least in the small area of application. This might not set a big plant back very much but could kill a young plant.

I'd either mix it in more water or apply it dry and water in with liberal amounts of water.

What does your fertilizer say is the total S content of that fertilizer? I'm curious if that's 21-0-0 plus 24% additional S.

I treat my plants with one ounce of ammonium sulfate three times a year.......once at bud break, once in May, and once in June. I weigh out an ounce then sprinkle the granules around the drip line of the plant and then rake it in. It really makes them grow, huge difference and it helps drop the PH of my soil which is slighly on the high side. There are lots of good articles on how to use ammonium sulf for blues, most recommend starting out with a small amount of fert and going up for each additionial year of plant growth..........older plants get more than younger plants. I know some here mix the ammonium sulf in water before applying it. I tried that and it seemed to work fine too but now I just sprinkle it around the base. If you are using a soiless mixture (pure bark, peat, etc.) you might also consider using an organic or soluble fert made for acid loving plants to be sure you are providing all of the needed nutrients. One of the biggest benefits of using ammonium sulf is its helps drop the soil PH.

Good luck.

RM

fruitnut: Yes the Honeywell Sulf-N ammonium sulfate soluble (21-0-0-24S) per the spec sheet contains Sulfur (as S), % 24 min. So you apply only 1 tablespoon per plant? What age are your plants? I like the idea of spreading the soluble fertilizer and watering it in while avoiding run-off.

The link attached has a fertilization chart for reference. For 4 year old plant and older they're suggesting 2-3 oz in Mid-May and 1-2 oz in Mid-June.

riverman1: Now 3 oz per year sounds about right and it sounds like you break it into three separate applications. My ammonium sulfate came in soluble form so it's a fine dust and I don't have access to the granular or mid form.

My main focus on switching to ammonium sulfate is so I don't have to apply both blood meal and sulfur separately however this has worked great for years. However I've heard ammonium sulfate just like riverman1 said it really makes them grow.

Well my second thought is that if I'm currently applying 6-8 oz of blood meal (12-0-0) then I'd only need 3-4 oz of ammonium sulfate (24-0-0). However with the ammonium sulfate I'm more likely to need to split the application since it is instantly available vs slower blood meal method.

Has anyone over fertilized with ammonium sulfate and lost a blueberry? If so do you recall the application amount and age of plant?

Here is a link that might be useful: WSU EDU Grow Blueberries

BSmith:

Mine are potted. The dissolved 21-0-0 is applied once a week with enough volume to run through the pot. In between just pure rainwater. This is only on small plants where I'm forcing rapid growth. Once the plant gets some size, after 1-2 years, I apply 21-0-0 no more than once a month.

I've burned blueberries with several types of fertilizer on potted plants. The error was always by not applying enough water. None of the plants died. Water yours in well and you won't have a problem. The ammonium ion is strongly held in the soil, you won't wash it past the roots.

You should be able to find the grantulated form of ammonium sulf in your area. It is used as a lawn fertilizer and sold in 20-40 pounds bags here at Home Depot, Wal Mart, Ace Hardware, and most other farm-type stores. Just make sure you don't get one that includes an herbicide for weeds in the lawn.

I have never burned one of my blues using it as I have described above.

RM

BSmith, you asked if anyone had lost a blueberry by overfertilizing with ammonium sulfate and I'm raising my hand. In fact I posted about it a few years ago on the thread below, which gives amounts and more details. I lost three of six plants. I replaced them and got up the nerve to use ammonium sulfate again last year. I now understand that where I really went wrong was applying the sulfate dry to the drip line and not watering it in. I may have used too much but I still think I would have been OK if it had been well watered. I think I even applied it during a dry spell when there wasn't much rain. So yes, be cautious. I like the recommendations here of mixing with water first and that's what I think I'll do this year.

Here is a link that might be useful: Overfertilized Blueberries

Here is the guide I have used when determining how to apply ammonium sulfate. Product of Oregon State University. Some very good reading here and a great reference source. I have applied 1 ounce per plant sprinkled around the drip line last year and it worked fantastic, lots of vigorous growth.

http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/12202/ec1304.pdf?sequence=1

In late April of the planting year, apply 0.2 oz
of nitrogen (N) per plant (equivalent to 1 oz of
ammonium sulfate fertilizer, 21-0-0, or 0.4 oz
urea, 46-0-0). Add the same amount of N fertilizer
in early June and in late July. Sprinkle the fertilizer
evenly within 12 to 18 inches of each plant, but
not directly on the crown or stems.
Ammonium sulfate and urea fertilizers contain
no phosphorus (P) or potassium (K). In general,
home garden soils have sufficient P and K.

In the second year, apply 0.25 oz of N per plant
1.2 oz of 21-0-0 or 0.55 oz 46-0-0) in April, May,
and June. The total amount of N applied per plant
will be 0.75 oz. Spread fertilizer evenly around
the plant, over an area approximately equal to the
spread of the bush. Try not to apply fertilizer to the
base of the canes.

In year 3, increase the total fertilizer N applied
to 0.8 oz. Divide the total into three equal portions
and apply one-third each in April (around bloom
time), May, and June.

In year 4, increase to 1 oz per plant. As the
planting ages, slowly increase the total N applied
to a maximum of 2.5 oz N per plant (12 oz of
21-0-0) in mulched plantings. Continue to split
the total into three applications in April, May, and
June. In general, you should not fertilize after
July 1.

Your visual assessment of plant growth and
fruiting can help you know how much to fertilize.
If the plants are growing well (10 to 12 inches of
new lateral growth each year and new vigorous
growth from the base of the bush), leaves look
green, and yield is good, there�s no need to worry
about whether plants are getting enough nutrients.
This assumes, however, that you�ve pruned plants
well. Added nitrogen fertilizer will not compensate
for poor growth due to insufficient pruning.

Check the soil pH every year or two, especially
if growth is poor. If the pH is above 6, you can
apply elemental sulfur to the surface of the soil
or mulch to slowly acidify the soil and improve
blueberry growth. Apply no more than 5.5 lb S per
100 feet of row (3 oz/plant). Higher rates will burn
or kill blueberry plants.

RM