AMMONIUM SULFATE for BLUEBERRIES

@thepodpiper Those blueberries look great, nice pictures! I like your netting too, good for you.

I’ve been alternating (NH₄)₂SO₄ 1TB / 2.5 gallons of water every 2 weeks, every other 2 week period I’ve been using Holy Tone, having great results this season.

I thought I’d revive this old thread with a new question.

I have 10 or 12 established blueberries that are doing well and I’m preparing the ground for 3 more. In looking up some soil prep/fertilization information ( http://smallfarms.oregonstate.edu/sites/default/files/growing_blueberriesi.pdf ) and they talk about sprinkling ammonium sulfate around the plants and not mixing in it water as discussed in this thread.

Does anyone have any thoughts about which is better?

I’m using it to try to keep the pH low (especially in the new planting but I don’t want to do more harm than good. I have both high bush and low bush and in the past I’ve just been sprinkling Soil Acidifier around the plants a couple times a year, but I have some ammonium sulfate and I figured I’d use to.

I have always been lazy and just sprinkled it around. I haven’t killed any bushes. I suppose mixing it with water would be more accurate.

If you guys remember, it was part of the back and forth that included Bamboo Rabbit ( who is now unfortunately MIA)

He is still around and runs the fig forum https://www.ourfigs.com/

He had a separate section for BB’s for a while.

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IIRC the gist of our old thread was to use AmSul to both fertilize and to help counteract alkaline soil and water. I think the article you linked talked about correcting pH first with sulfur and then using AmSul for just fertilizing. Probably fine if you have acid trending soils to begin with and plenty of rain (which is probably a bit acidic too) as they likely do in W’ern OR.

It’s probably fine to put it directly on your soil as they recommend as long as you are dealing with the pH issues in some other way (Sulfuric acid in the water, sulfur on the soil, etc). If you’re not, then adding the AmSul to the water to acidify it might be an easier way to go.

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Recommended dry application rate appears to be 1 oz. for each year that the plant has been in the ground. Don’t apply more than 4 oz. per plant and don’t apply the first year in the ground (root burn). One tbsp. of ammonia sulfate is about 0.5 oz, both by weight and volume.

That would be 8 tbsp. per mature plant. That seems like a lot for a single application. I would be concerned about unpredictable rain.

I agree. Seems like a big dose at once. Multiple applications of smaller amounts work better and safer.

I apply about 5# of Ammonium Sulfate to a 300 foot row containing 100 five year old plants three times which is about 3/4 of an ounce per plant per application. I would be afraid to put all the fertilizer out at one time.

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This is an old thread but I was hoping you could clarify how much Ammonium Sulfate you use. In a search for it I found you previously said:

But in this newer post you say you use 3/4 oz per plant three times per year?

I am planning on using small apps of Ammonium Sulfate + Elemental Sulfate spread over 3-4 times per year to reduce my soil pH from 6.3

I use copious amounts during the growing season, about 2 cups per bush, watering it in well, as often as I remember to do it. In our soil not doing enough is way more harmful than doing too much. The bushes have responded by exploding in both growth and production.

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I only use AS at the beginning of the season when I want to give a big quick boost of Nitrogen, after that I switch to a locally made blueberry / citrus 14-9-11 blend ($12 per 50 pound sack). I have used Hollytone in the past, but it just takes too much and it does too little, I currently have 2 mature 30+ year old rabbiteye blueberry bushes, as well as another 14 bushes that have been in the ground 3-4 years, some planted from 3 gallon containers, some bare root, most rabbit eye, though a couple of southern highbush (sweet crisp, indigo crisp, etc.). Native soil pH here is about 5.7, and so is the well water.

Better check my math!

I apply about 5 pounds of Ammonium sulfate over 100 plants (about 1000 sq feet) several times. Normally 2X in the spring and once after harvest. The application after harvest is important to produce more fruiting wood for the next season.

This year I plan to use substitute some 17/17/17 on the SHB because my PH is down to 4.5 and I need some K.

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Why not Urea.

If you need a larger quantity of AS, be sure to check with your local agricultural fertilizer dealer. I picked up about 700lbs for less than $200 last fall if I remember correctly… Guy I got it from will sell as little as a full 5gallon bucket, but some places will only sell by the ton.

I try to avoid Urea due to potential of biuret toxicity, particularly in my citrus

Figured I would share this very detailed publication about blueberry fertilization I found by University of Georgia.

University of Georgia - BLUEBERRY FERTILIZATION IN SOIL.pdf (54.5 KB) (source)

Here is a screenshot of a table in the pdf for the app rates of different fertilizers at different growth stages. Its a bit confusing but I think the amounts indicated for AS are for one application done in the summer.

image

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Thank you for the comprehensive info. Looks like I need to up my rates because my SHB are getting a lot less N what is recommended.

I apply about 5#/100 plants but it looks like they suggest about 25 pounds for 100 six year old plants.

My SHB have never been as vigorous as my Rabbiteye and perhaps the lack of Nitrogen is part of the problem.

If you didn’t see it already you might also find the “Differences in rabbiteye versus highbush blueberries” section of the publication relevant:

Young rabbiteyes will grow fairly well with just two to four fertilizations per year (Table 2 and 3), but will probably grow faster with light doses of fertilizer six to eight times per year (Table 4). In non-irrigated young fields fertilize modestly. Fertilizer salts can increase drought stress. […] Mature rabbiteyes generally need only two fertilizations per year. […] Southern highbush and highbush blueberries generally need more frequent fertilization than rabbiteyes to keep both the young bushes and mature bushes healthy. Young bushes should be fertilized every 4 to 6 weeks (five to eight times per year) and mature bushes about four (north Georgia) or five times (south Georgia) per year.

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Fixed the broken link to the PDF in my post above. Going to start saving and uploading PDFs directly to here instead of linking to them because for some reason extension office websites really like moving their files around.

Also found this less technical but also more readable PDF while looking for the last one:

[uga.edu] Circular 1163 - Blueberry Fertilization.PDF (522.1 KB) (source)

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