Blueberries with 5.6 pH native soil?

7 years ago

I am looking for your long term thoughts and advice on growing blueberries in soil that has a pH slightly higher than ideal, it is a 5.6 pH fine silty sandy loam soil that is moderately well drained located in SW Louisiana. I know blueberries can grow here without soil modification, as I have 2 unknown varieties of rabbit eye blueberry bushes that are at least 20 years old, maybe even 30 that went untended for several years. Over the last year I have been working on systematically pruning back the old minimally productive wood. They however are not the main topic of this message, I have also added about a dozen more blueberries over the last 18 months or so. First 3 that were in 1 gallon pots, then 3 "2 year old" bare root Pink Lemonade blueberries, that I suspect were more like 1 year old, then finally 8 that were in 3 gallon pots last October, overall a mix of rabbit eye and southern highbush. Most were planted in holes with roughly equal proportions of native soil, aged pine bark fines and peat moss.

So far all have survived, but I am not sure they are thriving as well as I would like, growth particularly on the Pink Lemonade has been minimal after a year in the ground only one is over 12 inches tall. So I am looking for thoughts on what I should do to either fertilize, amend the soil, or both.

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Comments (3)

Barrie, (Central PA, zone 6a)
7 years ago
Hold back on adding fertilizer around young transplants. That would likely do more harm than good. There are many reasons why plants are not growing as you might expect. Assuming you did not plant too deep you want to make sure plants have gotten adequate water. The pH is marginal but that alone should not be hindering growth. Are leaves of good color?
gardengal48 (PNW Z8/9)
7 years ago
I wouldn't even consider the soil pH to be marginal - it is perfectly adequate for growing blueberries. While they prefer a strongly acidic soil, they do not require it. We grow a great many blueberries in my area, with numerous commercial berry farms (including one of the largest wholesale growers of blueberry plants for retail sales in the country) and our native soil is only slightly to moderately acidic (5.6-6.5) - blueberries thrive here without additional acidifying amendments.
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You will need to find out the pH of your native soil, and the pH of your tap water, in order to get these blueberries on the road to recovery. Blueberries can tolerate pH up around 6.5 if the soil contains enough vegetable fiber to support fungal activity. They do better with pH between 4.5 and 5.5, however. If you are irrigating these shrubs with tap water, and you have hard water with pH over 7, you can add either white vinegar or sulfuric acid to your tap water, and lower the pH of the water to 5. This must be done with caution, it is easy enough to kill a blueberry shrub with too much acid. If your native soil has a pH over 7, it will gradually raise the pH of your blueberry patch. I use agricultural sulfur to lower soil pH, because it is slow acting and therefore easier to control than other methods. Bromocresol green indicator, yellow at 3.8, and blue at 5.4, is the least expensive way to gauge soil and water pH that I know of. A two dollar bottle of dye indicator might allow 50 or 100 soil tests to be completed.
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Pretty confident -- my General Hydroponics test kit (dye indicator) suggested that the pH was at or below 4, so I bought some bromocresol green to double check and get a more accurate reading. The latter put the pH under 4 but above 3.5. I'm also reasonably sure that it's not water related. They're all in bark based mixes (70% to 90% aged pine bark) and fabric pots that drain very well. That being said, I observed the worst bout of chlorosis this spring right after a day of heavy rain. Even so, the roots should still have had plenty of air given the porous mix and pots. To provide a bit more context, this has been an off and on again problem for me over the last couple of years. Last year, I discovered that I had what appeared to be a bad batch of pH test strips, and I switched to the GH test kit mentioned above. It strongly suggested that I'd been adding too much vinegar to my irrigation water, so I backed off considerably (to 1 tsp per gallon). I never fully trusted it, though, which is why I bought the bromocresol green. Now that I've done pour through tests with the latter and gotten similar results, I'm much more confident about the readings. What's curious is that I've never added sulfur to my potting mix (bark/peat/perlite) nor sulfuric acid to my irrigation water -- just vinegar. My well water isn't especially high in bicarbonates, and the pH tests right at neutral to maybe slightly acidic. Perhaps vinegar has more staying power in my particular circumstances? I've always operated under the assumption that its effects are temporary since organic acids are metabolized by microorganisms, but there's got to be some explanation for what's going on here. Of course, there could still be something that I missing or misunderstanding, but the dye indicator appear to be quite clear. So far, I'm basing my conclusions on pour through tests on two pots. Perhaps I'll test a few more today... This post was edited by shazaam on Mon, Jun 30, 14 at 7:30
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Drew, how do you know this is a long term problem not resolvable with mulch alone? Well most do not urinate on their plants, and need some way to be fed. It wasn't worded very well. Guilty as charged. I'm also concerned about micro-nutrients, as in my area we are low in manganese. Any wood from the area will be too. I have no way of knowing if the wood suffers from any deficits. I know Holly-Tone is a complete source of nutrition and it would ease my mind. You offered no source of nitrogen in you first post, urinating on my plants would result in my arrest in my neighborhood. I myself do not use woodchips. I have to pay for them. And for me I fight to keep the ph low. I would not use them for that reason. Not that chips are basic, it's just not acidic. I would rather pay for a more quantified fertilizer, blame it on the lab rat in me. Using wood chips though is a good idea in this situation, oh wait I already said that. I must admit I find your solution rather unique and quite humorous too. I usually try to avoid breaking the law when feeding my plants. I realize laws vary, here it is illegal. My bad for assuming it was in this situation, I guess I should have asked. I myself would avoid it even if legal. I'm on a couple of medications, and would be concerned about the quality of the urine. I would avoid if you're on any antibiotics at the time too. most are broken down but a few do leave the body intact. Especially say if you have a bladder infection, that antibiotic is meant to enter the bladder intact. I forget which one it is? It still may be fine, I really do not know? I try to avoid unknown situations. Also an unknown is the amount of nitrogen I'm adding. It would be trial and error, like would you suggest 2 minutes of fertilizer? I guess that would depend on the flow rate of your stream. When I was younger one minute would probably suffice. I could take a measuring cup with me. Let us know the rate per plant. I would not want to go willie-nilly on my plants. I also found the chemistry useful as I avoided using sulfates on my basic loving plants. Now I know I can use some. I also like to know what I'm adding does, and so as general info is very useful. This post was edited by Drew51 on Tue, Dec 2, 14 at 8:17
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garybeaumont_gw
7 years ago
Since I do not plant blueberries in the ground, I referred to William D Adams book Growing Fruits and Nuts in the South. He was a county extension specialist I believe from Houston.

He suggested putting out 1 oz per plant of 13-13-13 in March with 1 oz of Ammonium Sulfate(21-0-0) in April, May, and Sept. the first year.

As long as you are using fertilizer that is for acid loving plants (ammonium sulfate) it should keep the pH down in our area unless you are using well water. In Beaumont the bicarbonates, which can bring pH up, is low. Anything less than 92 ppm of bicarbonates is considered low, and anything over 153 is not recommended. Well water may be higher in bicarbonates.

I like to add a little fertilizer once a week. I use 1/2 teaspoon per gallon of water. I now use Peters Professional 21-7-7 for acid special. I got it for about $40 for a 25 gallon bag. It is expensive but less than Miracle gro Miracid.

The reason your blueberries may not be growing well could be aged pine bark fines could have taken some of the nitrogen out of the soil. That should not be a problem this year.

Since your plant have either been in the ground for over 12 months or were from 3 gallon pots, they are going to need nitrogen this year. Usually with bare root fruit trees it is suggested not to fertilize the first year. But with these already being in the ground for 6 months, they will need a little fertilizer.

I know with container blueberries it is recommended to apply ammonium sulfate with water and on the plants when they are moist. Putting the fertilizer out in a dry container can burn the roots.

Blueberries with 5.6 pH native soil?

Comments (3)

Barrie, (Central PA, zone 6a)

gardengal48 (PNW Z8/9)

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