silicaAugust 3, 2011

The use of vinegar is frequently written about on this forum for use as a soil acidifier. Below is the results of research at Minnesota University.

Dr. Jeff Gillman PhD

Associate Professor

Department of Horticultural Science

University of Minnesota

After research on vinegar as a soil acidifier by Dr.Gillman, he stated "In a nutshell, it just doesn't work well at all. It takes a lot of vinegar to change the pH, and the change is really very brief.

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You really believe this?



    Bookmark   August 3, 2011 at 8:38PM
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Her is something from the

Deoartment of Physics University of Illinoise at Urban Chanpaign.

This place says otherwise.

Thanks though:-)


    Bookmark   August 3, 2011 at 8:50PM
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greenman28 NorCal 7b/8a

Who here says they use it for a 'soil' acidifier?

Vinegar is used to lower the pH of water/fertigating solution, not the media itself.
Silica, have you missed that this whole time?

No one is recommending dumping vinegar on their raised beds or lawns.


    Bookmark   August 4, 2011 at 12:15PM
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fruitnut Z7 4500ft SW TX


I can't have everyone picking on you. As a long time blueberry grower, I'm going to believe the professor of horticulture, not the dept of physics. What's the dept of physics doing working with vinegar anyhow?

Vinegar keeps citrus happy because citrus really doesn't need low pH. Listen to the blueberry growers, they need low pH.

Here's the problem with vinegar. It's effects are temporary just like Dr Gillman says. It's an organic acid and when the soil bacteria break down the organic portion of the acid, the pH goes back up.

My citrus is very happy without vinegar or any other acidifier. With blueberries I'm always fighting pH. Vinegar on blueberries is a temporary solution until something like sulfur kicks in.

    Bookmark   August 4, 2011 at 2:57PM
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Hey Fruitnut:

You are right about vinegar being only temporary. I can vouch for that. I have to use it at least once a week to keep my plants looking as green as they do because the pH of my tap water is at 8.5.

After two weeks without it, the leaves on most my plants, especially citrus and gardenias loose their rich deep green color and start to look nutrient deficient. You know, the yellowing of leaves, leaf drop, lack luster color, and pest invasion.
The local nurseries have to lower the ph solution of our local tap water, or they have severe issues with their plant stocks. Unfortunately they can't sell their product publicly and the owner told me using vinegar was the best route in this instance but that I would have to do it frequently.

After reading that article, it seemed that article was talking about ground citrus/plants and not so much potted ones.
I have seen how green the ones are that come from Four Winds and I am friends with the owner there and he gave me the key to growing deep green plants and I tend to believe him who has been growing citrus as dark green as they are for over 30 years. If it wasn't for this small/huge bit of information no one has ever told me, mine would still be less than vibrant in my area.

Where can one buy this Sulfur anyway for the public? It sounds like a great product to use. That must be what the local nurseries use. It never occurred to me to ask
I was thinking of planting some blueberry bushes next year in containers.



    Bookmark   August 4, 2011 at 3:53PM
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are you saying that the Four Winds gave you the tip of using vinegar in tap water?

I just started using when watering my citrus. One squirt bottle of Foliage Pro and another with vinegar.

BTW, sulfur is available in 5lb bags from wherever you buy Espoma. The bag is labeled Espoma Garden Sulfur.

    Bookmark   August 4, 2011 at 5:18PM
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fruitnut, I am also a blueberry grower. Blueberries are THE acid loving plant. I understand the constant attention it takes to maintain a the plant's 3-4 pH. Concerning the Illinois link, the author Tamara made this statement..."vinegar contains a lot of acid". Tamara evidently does not know much about vinegar because vinegar certainly does not contain much acid at all. Vinegar is 93 - 96 percent water. It contains only 4 to 7 percent acid. It is so weak a person can safely consume it.
I would like to make another point. I personally know Dillon, Dillon is the owner of Four Winds Growers, he took over Four Winds after his father, who started the company, retired. I can guarantee you that Dillon does NOT USE vinegar. My guess is that he would laugh at any suggestion that his company would ever consider vinegar as an acidifying agent.

To verify the poor use of vinegar as an acidifier in container culture, one only needs to use their pH meter. It is a very easy procedure. Using a teaspoon, or even a tablespoon of vinegar per gallon water, does not last a week, but rather perhaps a day maybe two at the very most, but I doubt it. The higher the organic material in the potting soil, the quicker it will bio-degrade.

I grow a lot of citrus, both in the ground and some in containers. Like fruitnut, and the majority of citrus growers, I never use any ingredient to acidify the water, nor potting soil. After all, citrus are NOT low pH plants, they do not require an acidifier. A pH of 6.5 is not considered acidic, it is as close to a neutral pH as possible without actually being at 7. Citrus do fine at a pH of 7 or 7.5. Many of the world's citrus groves are growing in soils with a pH of 8+ and still produce excellent crops.

    Bookmark   August 4, 2011 at 6:06PM
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fruitnut Z7 4500ft SW TX


I agree with everything you said. I'll also say that I see nothing wrong with using vinegar on citrus. I'm sure those using it have fine looking plants, probably better than mine. But I grow for sweet fruit not as an ornamental. Some people want their plants to grow nearly continuosly and I'll agree they look better when growing. I don't want mine growing all the time. The plants get too big and besides the fruit off a plant pushed to grow all the time probably isn't as sweet.

Different strokes for different folks.

    Bookmark   August 4, 2011 at 7:02PM
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tapla (mid-MI z5b-6a)

Vinegar and citric acids are indeed poor as remedies for mineral soils (because of their high buffering capacity) with high pH, Which is undoubtedly what Dr Gillman was referring to, but they are both very effective and inexpensive ways to temporarily lower the pH of the soil solution in container culture, 'temporary' being all the container grower needs. Acid injection is used on a regular basis by commercial growers to lower soil solution pH and curb the tendency toward the upward creep in pH of soils irrigated with alkaline water, so there is no reason to believe it wouldn't be equally effective when regularly mixed into the irrigation water or fertigation solution by hand.

I can attest to its effectiveness by offering the fact that during the winter, I often see Fe deficiencies in plants under lights because I'm not able to flush accumulating dissolved solids from the soil as effectively as in the summer when I'm watering with a hose, which causes a rise in media pH and the precipitation of Fe into insoluble compounds. Acidifying the irrigation water with vinegar or citric acid lowers soil solution pH and makes Fe (and other minor elements) more readily available, evidenced by an easily observed change in the color of the foliage of 'tell' plants after acidifying the irrigation water.


    Bookmark   August 4, 2011 at 7:52PM
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Once again you misconstrued by words and my kindness here.
Seriously, you don't like me no matter what and it's obvious. I am done. It is not about helping, it's all about you against me since the Coco episode.
Sorry for posting on your thread.

I never said they did use vinegar. Reread my post before you fly of the handle an accuse me of saying something otherwise.

If you don't want to use vinegar then don't


    Bookmark   August 4, 2011 at 8:31PM
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Four Winds probably uses a stronger acidifying agent such as muratic or hydrochloric acid with their watering system. I can imagine it is quite large. It would be interesting to know what they use.

While vinegar may break down in a week or two, that could be all the time needed for nutrients to be absorbed by roots.

Mike's foliage certainly looks luscious and green. I don't mind following what he does!

    Bookmark   August 5, 2011 at 8:14AM
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Muriatic is hydrochloric, and it is doubtful that they use that due to the chlorine. More likely, sulfuric acid is used. Which is why sulfur is used to acidify soils for blueberries. Nasty stuff, therefore not available to the novice.


    Bookmark   August 5, 2011 at 8:48AM
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Duhh.... Sulfuric acid would be a better choice. Should have thought of that. But it can be very hazardous.

    Bookmark   August 5, 2011 at 10:49AM
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tapla (mid-MI z5b-6a)

The most commonly used acidifying agents for injection systems are sulfuric, nitric, and phosphoric acids because they acidify, reduce carbonates/bicarbonates, and supply essential nutrients. Which acid is most appropriate is most often determined by a combination of data from irrigation water analysis, tissue analysis and by considering the target NPK ratio and the acid's impact on the levels of nutrients it contains.

The primary goal of acidifying irrigation water and fertigation solutions isn't to reach an end point pH of the water; rather, it is to achieve a sort of stasis where the water has no effect on raising or lowering the pH of the soil solution.

Vinegar and citric acids are particularly good choices for hobby growers to add to their irrigation water and fertigation solutions because they acidify w/o adding nutrients that need to be accounted for as a fraction of the TDS in the soil solution. IOW, if the hobby grower was conscientious enough to wish to acidify the water supplied to his plants, it would follow that he would also be conscientious enough to make allowances for the nutrients in the acids. E.g., if the hobby grower used nitric or phosphoric acid to acidify his water, he would have to adjust the amount of N or P supplied in his nutritional supplementation program. As you can imagine, the calculations can be bothersome and difficult for those w/o a background in chemistry, and the problem of deciding just how to fertilize using what's readily available can also be a challenge. Using vinegar or citric acid as the acidifying agent eliminates the calculations and allows us to use a fertilizer in the ratio of our choice with confidence that the ratio is not being skewed by the acid used.

It should be noted that describing blueberries and other plants as acid-lovers is probably a bit of a misnomer. Blueberries will grow perfectly well at rather high pH levels if you can limit the availability of Ca. The plants we call acid-lovers have adapted to acidic soils. Their need of calcium is still the same as any other plant, and their nutrient requirements do not differ from plants that thrive in alkaline soils. The problem for acid-loving plants is that they are unable to regulate their calcium uptake, and readily absorb too much Ca when available, resulting in cellular pH values too high. Some 'acid-loving' plants also have difficulties absorbing iron, which is tightly bound in alkaline soils, another reason why they thrive in low pH soils. Note that this all pertains to the plant's ability to handle nutrients, and not to the actual nutrient needs of the plant.


    Bookmark   August 5, 2011 at 1:54PM
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MeyerMike, writing this thread has nothing to do with whether I like or dislike you. I don't know anything about you, as I have never met you. I would say reading your postings, you seem to be a very nice guy.

Al wrote, "Vinegar and citric acids are particularly good choices for hobby growers to add to their irrigation water and fertigation solutions because they acidify". I respectfully and completely disagree with Al, as it simply is not the fact. As University studies have shown, I and the vast majority of growers certainly agree, vinegar is unfortunately worthless as an acidifying agent. It has a useful life span of approximately just one day (depending on the type of potting soil being use). I only posted this thread to alert the hobbyists on this forum, who though that vinegar was a valuable addition to the care of their trees, when in actuality vinegar is giving them back nothing in return. I have not look into citric acid, as I have never heard, nor have I ever met anyone who ever thought of using citric acid. However, citric acid is again an organic acid. As an organic acid it too would biodegrade very quickly.

Al many growers stay away from nitric acid, as it is shown to be too corrosive to their systems. In our area, very few growers use anything as an acidifying agent. Those that do use phosphoric acid.

One last point. It seems many people on this forum are acidifying their trees. A citrus tree growing in an overly acidic potting soil, shows no general toxicity symptoms that one can pinpoint. What results from growing a citrus tree at a too low pH is that the tree produces a lush foliage growth with good coloration, but because of the low pH it produces a crop of few fruit, a container tree might not have fruit production at all.

    Bookmark   August 5, 2011 at 5:24PM
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tapla (mid-MI z5b-6a)

Someone sent me a link to Dr Gillman's article, and I can say with assurance he wasn't talking about container media, so quoting him is taking his words out of context and misapplying them to container culture. It might be interesting to take the discussion to his 'comments' section after his offering and see what he has to say. ;-)

I can also say with certainty that vinegar is not worthless as an acidifying agent, as I can easily see the direct results of incorporating vinegar into my fertigation solution. That one person SAYS it is ineffective isn't going to sway me when I have the practical results in front of me that show otherwise. I've used vinegar and citric acid (primarily in the winter) for a long time, and I definitely see the difference ...... and I'm a person who, if something flies in the face of science, will doubt my own observations or look to other reasons for the cause of what I'm seeing. In this case, there is nothing else I can think of that causes an almost immediate chance in foliage color (cures anemic/chlorotic foliage) when I add an acidifying agent to my fertigation solution to lower pH to somewhere between 5.0-5.5.

Physiologically speaking, I can't see how an overly-acidified medium would produce lush growth sans the fertility required to do so, which would require over-fertilizing and be attributable to grower error; but I can say that it's a leap to assume that all hobby growers that use an acidifying agent are using too much. We have two issues with the primary argument - the first is that low pH causes lush growth (it doesn't) and the second is the assumption that everyone is "over-acidifying".

The goal of acidifying irrigation water and fertigation solutions is to make (primarily) micronutrients more available. Whether the vinegar breaks down in a day or a week or an hour doesn't matter. Since folks are usually acidifying irrigation water regularly, and can SEE the results of the effort, I really see no reason to change what is working well because someone thinks it shouldn't.

Finally, organic acids (humic, fulvic, phenolic .....) are very active biologic components of soils. In soil, these acids retard the leaching of essential nutrients by organically bonding them to colloidal surfaces (chelating) in the root zone, and they also have buffering effects on soil pH shifts. Not only do these organic acids increase absorption of nutrients essential to plant health, They additionally are known to improve plant respiration, photosynthesis, and root growth. And while adding acidifying agents to water & fertigation solutions for containerized plants is primarily focused on managing pH-related issues, it's not a leap to think it possible that they also bring some of the benefits that many other organic acids provide in addition to their help in managing pH-related nutritional issues. I know I don't intend to stop using it any time soon.


    Bookmark   August 5, 2011 at 8:21PM
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Al, over the past I've read many of your postings, on the Garden Web, and the old UBC forum. I would say your knowledge is quite a bit greater than most people that visit public forums. A person can apply what ever elements to their plants that they wish. It just that some ingredients, although they don't do much harm, can also provide no benefit. I guess the best action to take at this point concerning the vinegar issue is simply to agree to disagree. Pour all the vinegar you wish on your tree. Success to you and your trees.

    Bookmark   August 5, 2011 at 9:13PM
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redshirtcat(6a MO StL)

Silica - the average pH of my water is 10.2. Most of my plants are grown soilless media in containers.

Since they are in containers they need to be watered quite often. In this summer heat that means for larger trees (10' now) at least twice a day when the temps are above 95 as they have been.

Watering with muni tap water at a pH of 10+ twice a day would mean that my media would be sitting at around a pH of 10 most of the time.

We can agree that citrus trees don't like to grow in media with a pH of 10, yes?

So what do I do? I add 1 tsp of vinegar to my fertigation solution (injector) and my new solution is usually around a pH of 6.0 (actually I also add FP which drops the pH slightly more since they use phosphoric acid in it).

Does the vinegar last a week? No - but I don't need it to. I need the pH adjustment to last for about 12 hours. When it gets cooler I might water every 2 days or maybe every 3 in the winter. Might the pH creep up then? Possibly - but it's still better to try to keep the pH out of the 10+ range, don't you agree?

All of my container citrus are productive - my largest tree in a 30" pot right now has 40+ lemons on it that are of mature size. It also got a 2nd crop during another flush and has 15 or so marble sized lemons.

Are you saying that you think people with muni water in the 10.0 range can get away with using that water on soilless container citrus without any mineral deficiencies?

Or are you saying that you think they should use phosphoric acid? I happen to have some phosphoric acid because I made some homemade foliage pro and I would use it but it's far more dangerous to work with than the vinegar and it's also less readily available to me in large quantities.

Or are you saying that people are just acidifying too much and you think they should keep their pH around neutral (as you've said in some other threads). I explained in that other thread, I think, that flying dragon has been shown to prefer a slightly acidic soil solution. I provided you the reference in that thread. Not that it matters since I would need to drop mine down from 10 anyway.

What would you have the home grower using a soilless media with citrus tree and 10+ muni water do?

    Bookmark   August 6, 2011 at 2:12PM
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fruitnut Z7 4500ft SW TX


Tell you what I'd do with 10.2 mini water is I'd call whoever is providing that and complain. Second I'd not drink it or apply it to my plants. You need a rainwater collection system. In St Louis it won't be hard to collect enough rain for all but the biggest operation.

How do you know your water is 10.2? That is extremely high for any fresh water source, well or surface. In fact it sounds out of the realm of possibility.

    Bookmark   August 6, 2011 at 2:27PM
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redshirtcat(6a MO StL)

There are 2 ways I know this:

#1: I check the Water Report from the County:

They note that the average is 9.8-10.0.

#2: I measure the pH of my water at least 4 times a week. Most often daily with high quality instruments. I keep them calibrated. They give me an average of 10.2. My water never drops below a pH of 10.

You can see from the report that the total alkalinity is only in the 100 range so it's not too terribly hard to bring the pH down but there you have it.

I would kill for a quality rainwater collection system that could meet my needs. I'm using about 100 gallons of water a day when the temps are above 95 - sometimes more. We recently had a 3 week spell without rain. It would take quite a bit of space to get a collection system up and running. There are cheap ways to do it with food barrels but to get the capacity I would need things would look very ugly and this is at a residence so I'm not going that route. When I get enough money set aside there is a vague plan to look into underground collection systems.

Also: I don't know much about water quality but I've been told from numerous sources that St. Louis has some of the highest quality muni water in the country. Whenever I go anywhere else I can't stand the taste of the muni water. It really is very good. I have no idea why the pH is so high.

Still waiting for an answer from Silica on what he would suggest people do in this situation if not vinegar.

    Bookmark   August 7, 2011 at 4:48PM
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It is PH 9.8 here in Austin. I wounder a complain to the city will make any difference. My plants love it after I started using citric acid.

    Bookmark   August 7, 2011 at 4:51PM
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redshirtcat(6a MO StL)

And while I'm thinking about it I just want to point out one more thing.

If we can agree that a pH of 10 in container soilless media is terrible for plants and that it should be acidified for best results then the question becomes what should the home-grower use.

You mentioned phosphoric acid silica and noted that the local nurseries use that if they use anything. Phosphoric acid is quite a bit more dangerous than vinegar. If you spill 52% P2O5 phosphoric acid on yourself you risk an acid burn that is nothing to sneeze at (immediately remove clothing, flush with water for 20+ minutes, call physician). If you spill vinegar on yourself... well then.. you've got vinegar on yourself.

Why does this matter? A few weeks ago something went wrong with my Dosmatic MiniDos injector. I still don't know what caused it but I noticed a distinct vinegar smell when I was watering a rosemary plant. The injector had massively over-injected and given a very concentrated jolt of vinegar to the plant. It was beautiful that morning - by the next morning it was a crispy brown. Totally dead. Now obviously the injector screwed up and that needs to be fixed - but if an injector screws up with vinegar you lose a plant. If it screws up with phosphoric acid and you happen to splash a concentrated solution on yourself? You've just bought yourself an acid burn. At the very least some serious skin or eye irritation.

Vinegar or citric acid are much safer and more readily available and both work great for the home gardener for fertigating container plants in soilless media.

This is what the vast majority of people who are talking about vinegar are doing. They aren't dumping it into their yards or expecting it to be a long-acting solution to soil pH issues.

    Bookmark   August 7, 2011 at 5:08PM
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The water source for Saint Louis comes from two sources, the Mississippi and Missouri river. Therefore, Redshirtcat could easily be correct when he says that his pH is 10.2. I would believe him. I have worked much of my adult life in the greenhouse industry, where pH is always a changing concern from one type of crop to another. The industry commonly uses four methods to lower a medium's pH. 1. Ammonium based fertilizers, 2. Acidification of the water source to reduce alkalinity, 3. Iron supplementation, and 4.Acid drenches.

1.Use a high ammonium fertilizer.
Select a high ammonium (very acid) fertilizer such a 21-7-7 (other listed below). The effect on medium pH can sometimes be slow, more than one or two weeks, when small plants are growing in large containers. Ammonium based fertilizers lower medium pH through the action of nitrifying bacteria that naturally occur in all potting soils, and also especially by the plant roots that take up the ammoniacal nitrogen. In both cases, bacteria and plants both release acidic protons (H+) into the media, resulting in a lower pH. Urea is converted into ammonium before being taken up by plant roots and is therefore also acidic. In general the higher the percentage of ammoniacal nitrogen in the fertilizer, the more acidic the reaction and the faster the medium pH will decrease. For example 21-7-7 (100% ammoniacal nitrogen) is more acidic than 20-20-20 (70% ammoniacal nitrogen), which is more acidic than 20-10-20 (40% ammoniacal nitrogen). Changing to a fertilizer that contains a higher level of ammoniacal nitrogen is usually a straight forward adjustment in the fertilizer stock solution, and the least drastic of all options for lowering pH. A drop of 1 to 2 full pH unites is possible in an actively growing plant over each two week period.

In redshirtcat's case he is using Foliage Pro as his fertilizer. Foliage Pro is not a bad fertilizer, but it is also not the best fertilizer for citrus. Anyway, Foliage Pro IS a bad choice in Redshirtcat's case, because it is a basic fertilizer which will promote a rise in medium pH over time. Ammonium lowers pH, nitrate raises pH. Foliage Pro is to high in nitrate nitrogen -- 2.9% ammoniacal (NH4) and 6.1% nitrate (N03).

Water alkalinity, is a measure of the acid neutralizing capacity of the water. Redshirtcats is lucky that his alkalinity (as CaCO3) is not exceptionally high. Irrigation water that contains high alkalinity can cause medium pH to rise over time, even when an ammonium based fertilizer is used. Acidification of the water, using a mineral acid (normally sulfuric, nitric, or phosphoric) reduces alkalinity. When a rapid change in medium pH is desired, alkalinity can be reduced to zero by simply acidifying the water to a pH of 4.5. Acidifying water to zero alkalinity, by itself, will not decrease medium pH. However, decreasing water alkalinity to zero, in conjunction with fertilizers high in ammoniacal nitrogen can be very effective at lowering medium pH. This is because with no alkalinity in the water, all the acidity produced by the fertilizer can react with the medium to lower pH. If there is alkalinity in the water, then a fraction of the acidity produced by the fertilizer will go to neutralizing the alkalinity, not reducing medium pH. Thus the more alkalinity left in the irrigation water, the less effective an acidic fertilizer will be at lowering medium pH. The advantages are that acidification to reduce alkalinity only requires a small quantity of acid. Water at pH 4.5 with zero alkalinity is highly unlikely to result in phytotoxicity. Be very careful about going below zero alkalinity. NOTE: Alkalinity test kits are no help because alkalinity test kits only measure to zero alkalinity, not below zero. If you reduce alkalinty to near zero in order to reduce medium pH, remember to change your acidification rate back to a more moderate alkalinity e.g. 80ppm total alkalinity, after medium pH has stabilized to the desired level.

Repeated weekly drenches with enough sulfuric acid to drop pH of the drench solution to 1.5 - 2.0 is an effective way to rapidly drop medium pH normally in one day, but this is also the most caustic and hazardous option for both people and the plant. Because of the high risk I do NOT recommend this method except with close supervision by the nurseries fertilizer expert. Acidifying irrigation water to pH 4.5 (zero alkalinity) in combination with ammonium fertilizers helps drop medium pH over time with less risk that a strong acid drench.


1. 21-7-7 Contains an acid producing quantity of 1,520 lbs.
per ton of fertilizer.

2. Urea = 1,400 Lbs./ton of fertilizer.

3. 25-10-10 = acid producing quantity 1,040 lbs./ton fertilizer

4. 9-45-15 = acid producing quality 940 lbs./ton fertilizer

5. 20-20-20 = 680-lbs./ton fertilizer.

6. 20-10-20 = 429-lbs./ton fertilizer.
There are other formulations of acid fertilizers but the acid producing quantities are too low to bring the pH down in a reasonable time period. THE HIGHER THE ACID PRODUCTION ABILITY OF THE FERTILIZER, THE FASTER THE pH IS LOWERED.

NOTE: This is how nurseries reduce pH. As you can imagine, no nursery would ever consider using vinegar. Whether you use mineral acids, or attempt some amount of possible success with vinegar, is up to you. Whatever, I wish you success with your trees.

    Bookmark   August 8, 2011 at 6:57PM
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redshirtcat(6a MO StL)

So in short your suggestion for the home gardener is to use an acid-forming fertilizer containing mostly ammonia or urea. Do you know of a complete liquid fertilizer that is urea or ammonia based that contains Ca and Mg? I don't believe it's possible as the pH of the fertilizer would be too high to keep the calcium in solution. I assume, then, that your suggestion would be to use an incomplete fertilizer and then supplement Ca as necessary?

I use Foliage Pro because it's a complete solution. I understand that 5-1-3 is the suggested ratio for fertilizing citrus but I have quite a few other plants and had to settle for a single fertilizer solution as I only have 1 injector.

The information above was useful but I have some questions. It is my understanding that it only takes a total of 10-20% of total N supplied to be in NH4 form for the effect of the fertilizer on soil pH to stabilize around 5.5 (all other things being equal). Foliage Pro supplies 33% of its N in the form of ammonia. So it is my understanding that the nitrates in FP should be having essentially 0 impact on soil pH. Is that not correct?

Some other questions:

In container culture isn't it the case that pH creeping up due to CaCO3 accumulation and etc is mitigated by watering until there is runoff? In other words: the soil is flushed on a regular basis unlike in-ground culture so upward pH creep from accumulated minerals is far less of a problem.

Some of the vinegar is, as you say, being neutralized by the CaCO3 in the water - or, put differently, the vinegar is dropping the alkalinity as you suggest. But the pH is also dropping and as such are there not H ions leftover after the neutralization that are still doing work in the soil? Remember: we don't need them to work for long in this scenario - just until the next watering.

In other words: if the pH of the fertigation solution is in the correct range and the NO3 isn't raising the soil pH because it is being countered by an appropriate level of NO4 then the soil pH should stabilize around the pH of the fertigation solution. Right?

    Bookmark   August 9, 2011 at 4:24PM
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redshirtcat(6a MO StL)

Here are a few studies that discuss the ratio of NH4 to NH3 in soils. You will see in the abstract of the first that they suggest a ratio of 40:60 of NH4:NH3 and that this gives a stable media pH of 5.9. Foliage pro is ~33%:66% - very close.

The 2nd link has a chart showing the effect of different ratios of NH4:NH3 on soil pH and notes that frequent watering with any of the ratios at a set pH didn't result in dramatic soil pH changes because the solution was brought back into the correct range at the next watering. This was true even with 100% NH3 fertilization.

Like the first study they note that 60% NH3 puts you in the 5.0-5.4 pH range.

Am I missing something?

    Bookmark   August 9, 2011 at 4:59PM
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fruitnut Z7 4500ft SW TX

Nitrate is NO3, not NH3. You might be confusing some people there. Otherwise an interesting discussion, thank you all!

    Bookmark   August 9, 2011 at 5:45PM
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redshirtcat(6a MO StL)

Grr, Sorry. NO3 is what I meant, obviously.

    Bookmark   August 9, 2011 at 6:24PM
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It is my understanding that it only takes a total of 10-20% of total N supplied to be in NH4 form for the effect of the fertilizer on soil pH to stabilize around 5.5 (all other things being equal). Foliage Pro supplies 33% of its N in the form of ammonia. So it is my understanding that the nitrates in FP should be having essentially 0 impact on soil pH. Is that not correct?
25% NH4 is the VERY BEAR MINIMUM . Remember the higher the NH4 the quicker the pH is reduced. In your case I would not use a fertilizer that contained any NO3 ((or at least VERY LITTLE) until your potting soil becomes stablizedAll of the NH4 formulations that I listed are completely water soluble fertilizers

In container culture isn't it the case that pH creeping up due to CaCO3 accumulation and etc is mitigated by watering until there is runoff? In other words: the soil is flushed on a regular basis unlike in-ground culture so upward pH creep from accumulated minerals is far less of a problem.
The more of your water that you apply it will be raising your pH.

QUESTION. Some of the vinegar is, as you say, being neutralized by the CaCO3 in the water - or, put differently, the vinegar is dropping the alkalinity as you suggest. But the pH is also dropping and as such are there not H ions leftover after the neutralization that are still doing work in the soil? Remember: we don't need them to work for long in this scenario
All that is happening is at "0" the number of positive and negative charges become equal. YOU NEED TO DO BOTH THE NH4 FERTILIZERS AND THE NEUTRALIAZTION.

ANSWER; NO3 fertilizers always raises the pH The higher the NO3 the faster the rise.

I really not have time to read you second post. However, every nursery in the USA does as I wrote in my above post. No exceptions. If you do not want to follow it then so be it. Regards.

    Bookmark   August 9, 2011 at 7:02PM
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How about peeing at the base of the plant? Too much nitrogen?

    Bookmark   August 9, 2011 at 7:08PM
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Redshirtcat, I made a typo error on my answer to you. The NH4 has to be at the very minimum 25 percent GREATER THAN THE NO3 CONTENT in the formula. Foliage Pro will never work in your case.

    Bookmark   August 9, 2011 at 9:51PM
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redshirtcat(6a MO StL)

mmm thanks for the information. I'm not trying to needle you - I just want to understand. If you say that all the nurseries do the above then I believe you but I'd still like to understand.

Yes - I see that 10-20% NH4 won't cut it - those studies and others I've found are saying you want to stay near the 40:60 NH4:NO3 range. So far every one I've looked at indicates that this should stabilize pH somewhere in the range of 5-6.

I guess I don't understand alkalinity very well. I thought the function of alkalinity practically speaking in this situation was to raise the amount of acid I had to add to a solution to get the desired pH. So if I started with a pH of 10 and an alkalinity of 100 I might need 1 tsp of vinegar to get to a pH of 6. But I might need 2 tsp of vinegar if I started with an alkalinity of 300 as CaCO3. In other words: I thought if the pH was dropping it meant that I was overcoming the alkalinity and that I had a net positive of H ions in the solution? I thought that's what pH measured...

I guess I also don't understand the difference between lowering the media pH and the fertilizer solution pH. Am I trying to lower the pH of the Calcined DE in my container? Or merely lower the pH of the solution of fertilizer and water that the DE is absorbing? If the latter then why wouldn't it be effective to just keep fertigating with a solution at the desired pH?

If the former.. and we're somehow trying to lower the pH of the calcined DE then I seriously misunderstand the goal here... is it even possible to lower the pH of a substance like that?

If you get a chance if you could look at the 2nd study I linked and let me know what you think about their finding that the pH stays within the desired range and then resets at waterings and what that means in terms of this discussion... I'd appreciate it.

    Bookmark   August 9, 2011 at 10:00PM
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My experience using vinegar (5% white vinegar, food grade) is with blueberry shrubs, not orange trees. However, this experience has been gained over 15 years. Our native soil has pH of 7.6, and our municipal water, from local wells, also has pH of 7.6. I tried to grow blueberries without a pH meter, but I was not able to control the chlorosis very well, although I could keep the shrubs alive. When I purchased a pH meter(Hanna Instruments) and began soil testing, I was able to keep soil pH between 6 and 7, consistently, and the chlorosis issues went away. However, I learned that the effects of vinegar added to irrigation water lasted only a month. Every spring, when I tested soil pH around the shrubs, it would be back up to 7 or slightly higher. I was able to purchase soil sulfur locally, but it was very expensive, around 3 or 4 dollars a pound, so I used it sparingly. Eventually, I realized that sulfur was better at lowering soil pH than vinegar. The sulfur must be metabolized by soil bacteria before it is converted to acid, and this takes about a year to be completed. After considerable searching, I was able to locate agricultural sulfur for sale at a nearby farmer's seed'n feed co-op, in 50 lb bags, at 90 cents a pound. Using larger amounts of sulfur, I have been able to get soil pH lowered to 4, and one pH reading was 3.5. The shrubs are very deep green, and growth rate is better than before. Unfortunately, we had so much rabbit damage last winter that blueberry harvest was very poor this season.

Here are my conclusions: 1-5% white vinegar, diluted properly, works very well for lowering soil pH, but repeated monthly applications are required. Food grade vinegar is readily available, safe to store and use, and relatively inexpensive. Plants seem to do well when vinegar is used to lower soil pH, so I suspect that it has a beneficial effect on soil microbes. 2-agricultural sulfur works very well for lowering soil pH, but it takes about a year for an application to be fully metabolized and incorporated into the soil. You will have to find a bulk source, in 50lb bags, to obtain it at an economic price. 3-pH can be tested with a calibrated glass bulb type meter, successfully, but these units are both expensive and fragile. Dye indicator solutions are less expensive, and they don't require calibration. However, indicator dyes are less precise, so a given test result will be "x" plus or minus 0.2 pH unit.

No one should conclude from the above that vinegar(acetic acid) is totally benign. 20% acetic acid is used as an herbicide. I have spilled 5% white vinegar on the lawn, and killed the grass in a few small spots. I am certain that one would be severly burned by exposure to glacial acetic acid(concentrated acetic acid). There really is no way to avoid quantitative analysis when using acids in horticulture. You have to count, you have to measure. Using our local tap water, here in Madison, Wisconsin, 6 fluid ounces of 5% white vinegar per 4 gallons of water is an appropriate combination for watering blueberry shrubs.

I still use vinegar once in a while, when I need to drench the soil and lower pH immediately. But these days, I might use one or two gallons per year, since I rely mainly on agricultural sulfur. It takes around 15 pounds of sulfur per year to keep the pH down on our 15 blueberry shrubs. The sulfur does not have to be dug in, all you have to do is pull back the mulch, scatter the sulfur, and cover it back up.

    Bookmark   August 11, 2011 at 11:30AM
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hoosierquilt USDA 10A Sunset 23 Vista CA(10b Sunset 23)

Yup, eric. This is what Mike is talking about. He and others use acidified water just as a temporary measure. For helping fertilizer be taken up better for example, and NOT as a long-term pH lowering solution. Soil sulfur is the way to go. Here in S. California, my soil and water are about the same pH, around 7 to 7.6. I plant all my blueberries in containers, as it is much easier to control the soil and the soil pH. I mix in 1/2 compost and 1/2 azaelea, camellia mix. I also mix in about a cup of soil sulfur (they're big terra cotta pots). I also top dressed with aluminum sulfate when I planted, and occasionally top dressed for the next few months until the soil sulfur kicked in. My blueberries are rich green and produced lots of blueberries first season out (I bought 1 and 2 yr. plants). I, too, had to manage for 4-legged pests, for me it was ground squirrels. I had to put hardware cloth cages around mine, as the #$%*& squirrels hopped right in and took a couple of the blueberries right down to the ground (lost one). After that, no problems from squirrels, rabbits or even birds. I never acidify my water, as they are all on drips, with an occasional deep watering when I fertilize. And frankly, because I am just too busy with a full time job to bother. They are gigantic, now. I planted in the early spring.

Patty S.

    Bookmark   August 11, 2011 at 1:00PM
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Thank you for your kind observation and simplicity for us hobby growers.
I should ever decide to grow in-ground, the other info will pertane to me and will be very beneficial.


    Bookmark   August 11, 2011 at 5:03PM
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