How do we acidify inorganic Bonsai soil?

Fore wrote:Jay, interesting thread. My sensei here told me to use Alum Sulfate, sprinkled on the topsoil. How much? He said like "heavy salt" on a dinner plate. But check pH first. Apply 1x/mos. This is using 100% Turface.

I would not want to question what your sensei is teaching you but I personally would never us Aluminum sulfate to acidify anything in a container. It takes many months for the acidifying reaction to happen in that time the plant derives no benefit from the compound and could easily begin to suffer toxicities. If you use aluminum sulfate on an azalea your liable to kill it. Most packages of Al2(SO4)3 warn never to use it with Rhodys or Azalea. Its meant for "in ground" use.

The only "sensei" I've ever seen use the product in Bonsai culture was master Wolfmeditation.......
-Jay

I've not seen it used with Azaleas, but with Pines. I'll check into my information again. Funny/strange that there's so many different experiences with various techniques. Part of the horticultural experience I guess

I use osmocote-they have different formulas for different plants, look for the one for acid loving plants-I know, it doesn't look pretty, but I found it very effective, and I am also a bit lazy about feeding. With osmocote, beware of lots of moss growing on the surface. As for azalias, I have found that Kanuma is still by far the best growing medium. I am unable to use organic fertilizers, too many critters visit our back yard

I've just re-read the entire thread as it is an interesting one.

For azaleas I must admit it is 100% kanuma for me but to quantify i only have one import tree (kaho). I feed with organic homemade cakes and soak the entire pot in full strength miracid (now renamed miracle azalea & camelia) about 3 times a year. This full submersion totally saturates the substrate and certainly maintains acid conditions in the pot. Here she is the year after I started the technique:

As jay knows i am a great fan of sphagnum and this year i'm using graded pine bark (5-10mm)in the soil mix as well. Both these are on the acid side but i dont feel they will actually maintain acid conditions throughout the pot. 30%-40% of my soil mix is kanuma and kiryu and both are acidic soils, so combined with bark and moss the acid components outnumber the neutral. If I was using a 100% neutral soil I would scatter sequestered iron onto the pot surface once a month, then feed and water with your choice of products for the trees current development. ( When you read the miracle grow web site it describes the 'acid' range as containing sequestered iron as well). Then every 6 weeks the entire pot would be drenched in a miracid solution through the growing season.

Many trees have a ph range 5.5-6.5 and i think to get these to thrive in a TOTALLY neutral ph soil you need to know and potentially control the acidity of the water used, either by treating the soil as mentioned, (but it will be steadily leached out), or treating the water itself would be the perfect solution.

If you think of real nature the plants that find the soil acidity to suit them thrive, where the soil is wrong the plant simply does not grow. Gardeners are always trying to grow acid loving plants (azaleas, camelias, acers etc) on chalky limestone soils and they are always battling aginst nature - needing to change the soil surrounding the plant, treat and drench the soil etc. Growth is never the same as the soil is always attempting to revert from acid due to overwelming neutral or alkaline conditions. This makes me personally conclude why make thing difficult and use a neutral ph bonsai soil that needs forever acidifying ? it is extremely easy to make an inorganic acid soil up afterall. Volcanic seams to be the key - what is the ph of the slopes of mount st helens?

cheers Marcus

If we could un-condition ourselves to re-think Ph as being water Ph rather than soil Ph we would all be well served.

You can grow any calcifuge in marbles if you like and as long as your fertilizer water alone was Ph'd into the preferred range for that species and it would thrive.

Its this understanding that allows us to break free of these overly complex soil mixtures and use one simple substrate if we wish.

But ultimately, I believe its true with fertilizers as with soil mixtures that it comes down to "whatever works for you" and should possibly be left at that. Though I will openly confess Marcus has got me into adding a little chopped Sphagnum to my Turface now.

-Jay

completely agree Jay -

the water ph is the key for maintaining pot ph conditions for trees you are aiming to keep evenly moist, but it could be less successful to rely on water/fertilizer ph for trees that you may want to keep much drier at certain times of the year. When tightening up the foliage I keep my pines and junipers very dry for periods of several weeks at a time, so i feel more comfortable knowing the soil mixture is on the acidic side without needing water based fertiliser to maintain it.

Whether we use one single substrate or a combination of 5 or 6 makes no difference really - if they all cost much the same per bag the total repotting costs remain the same, and in a typical year you'd need the same total volume too.( i personally love the idea of a little fine tuning of soil ingredients for specific trees needs, and as Jay points out it is down to personal confidence really) but i can look back to when i had too many trees and was working away a lot - back then to have a single soil and a simple fertiliser to keep all the trees living and ticking over would have been very appealing.

My only minor reservations from reading this thread about this product - it could hold too much water for refined trees that need dryer acidic conditions (pine & junipers mostly)- the moisture and need for regular acidic fertiliser will promote fast coarse growth in trees that need totally the opposite.. Maples fall half in/half out the category- they are acid loving, like the humidity but certainly dont want much fertiliser when you are getting the internodes and leaves down in size. I think non fertilising soil acidifyers will be needed to get the most from it as a maple soil.

really interesting thread

Marcus

Yeah to me it doesn't make any sense to use soil that has a pH inappropriatefor the plant used and then try to change the pH though fertilizer. The idea behind using pure gravel/akadama/inorganics is that you can't overwater or overfertilize. This should also mean you can't affect the pH.

Kanuma soil has low pH so if you need to lower the pH and for some reason you want to keep it 100% inorganic, you can use that.

Also, azalea don't just need something on the slightly acidic side. Ideal is a pH of 5.5 or so. Some plants would struggle with such a low ph. A ph of 6.5 is not what you want. That's why bonsai growers in Japan use 100% kanuma soil and that's why commercial growers all over the world use 100% peat.

I think that most minerals we relate to as being volcanic rock are akin to glass and both pH neutral and pH inert. But 'volcanic rock' is such a broad term, composition can be a wide variety of things.

Glaucus wrote: The idea behind using pure gravel/akadama/inorganics is that you can't overwater or overfertilize. This should also mean you can't affect the pH.

The soil has no Ph. It only produces a specific Ph reaction when it is put in water. Its the WATER that liberates a percentage of Hydrogen Ions that we measure logarithmically as a Ph, not the soil.

This is a pervasive misconception.

This is why folks like Harry Harrington are able to grow Pines, Azaleas and Boxwoods ALL with different Ph requirements, ALL in the same medium.
-Jay

So, if the soil has no pH, how can we acidify it-if its the water that needs to have a low pH then acidify the water. But that seems to be a very cumbersome way to go about it. It seems to me, that if you use an inorganic soil, such as turface, you have to fertilize from time to time for the plant to get nutrients. btw most water from municipal water supplies in the US have a pH of around 8-alcaline, so as not to corrode copper pipes. If you have well water then test the water and go from there.

Seems to me that there was some related/potentially useful info on this in a previous thread - help with beech leaves is the link for anyone interested.

Of course soil has pH. And minerals can have an effect on pH, though many are inert. When you have a generally pH inert inorganic mix that retains little water, it is all about the pH of the water you use. Something like 100% perlite would have no effect on pH at all. But minerals like kanuma, this mineral would release H+ ions into the water and lower the pH of the water. Other minerals like calcium carbonate would do the opposite and absord these ions.
This indeed means you can't lower the pH of the minerals in the soil. You can change the mineral you have in the first place, but that's a different story.
Remember though that only solutions have a pH. The minerals themselves don't. If you measure the pH of a soil with perlite, you aren't measuring the perlite at all, just the water.

But as said before, adjusting pH of water does seem cumbersome.

Clay(akadama, kanuma) has the effect on pH it has because it is partly soluable and it contains organic material, which will create more acidity when decomposing. Now I don't know what effect the baking has on that. But clearly when measured the pH of kanuma is 5.0 or so. So obviously picking the right soil is the way to get the right pH for your plant. In fact, it goes the other way around. Plants had to adapt to their enviroment because pH of the soil matters. It is not the rain they had to adapt to.

http://en.wikipedia.org/wiki/Soil_pH

Glaucus wrote:Of course soil has pH.

But minerals like kanuma, this mineral would release H+ ions into the water and lower the pH of the water.

I dont like disagreeing with folks too strenuously on the forum, as i have such great respect for everyone here. But soil science is a factually based science. In the case above the Kanuma's buffering capacity allows the WATER to release the free hydrogen ions. The soil particle itself does not.

Chris has an excellent suggestion in reviewing the "help with beech leaves thread" in which we were lucky enough to be able to pick the brain of a professional aeroponic gardener.

He recommended a book to me that I will recommend to you Glaucus that may help clear up your misunderstanding regarding soil Ph
"Understanding ph management in container-grown crops" by William R Argo, and Paul Fisher. Meister Publications.

best
-Jay

I don't know why you feel you have to make such a statement. Soil has a pH. And the idea that it is about the water you use and not the soil the plant grows in is strange to say the least. I have never heard of anyone watering azalea or rhododendron with water that was acidified. They all grow in acidic mediums instead.
I did my job explaining that to you. Kanuma will contain carbonic acid. That's a source of H+ ions right there. Now since I didn't do actual experiments myself and I can't find any studies that actually did it so I don't know what actually happens, I can't tell you more.

Feel free to tell me about your alternate theory wherein minerals cause water to release it's H atoms into H+ ions though because you didn't actually do that but rather referred to a book I don't have.

Well, as a chemistry professor (emeritus), I guess I have to step in here. I am not a soil scientist, and I cannot comment on the relative merits, acidity, etc. of kanuma or turface, but I seriously doubt that kanuma contains "carbonic acid". Carbonic acid is what you get when you add carbon dioxide to water (carbonated water): CO2 + H2O = H2CO3 (carbonic acid). As you will have noted, carbonated water goes flat upon standing. That's because the reaction also goes in the opposite direction to give carbon dioxide gas and water. You can have carbonic acid only in water (possibly water in kanuma), but dry kanuma will have no carbonic acid, and little if any carbon dioxide gas, other than what is normally present in the atmosphere.

Sorry for being so didactic.
Oliver

When organic material decomposes, CO2 is created. When this dissolves in water, we call it carbonic acid or H2CO3. I was under the impression this process is why acidic soils have the low pH they have. If I am wrong, please enlighten me.

I guess you will have to explain to me just what kanuma is. I was under the impression it was a vulcanic clay product. If so, it may well be acidic--I don't know one way or the other--but not by virtue of organic material breaking down. And, unless your bonsai soil mix is a stagnent mess, any carbon dioxide produced will vaporize out, or be washed out in watering. Yes, certain pine bark and other organic materials are acidic, but this is because they contain other organic acids, such as tannic acid, and, upon break down, produce humic acids, but I don't think carbon dioxide is the factor here. I really am out of my field here, so I don't think I should speculate further.
Oliver

Well, whatever the process is, I think we can at least conclude that the mineral doesn't ionize the water as suggested and that soil pH is important. And this is why all commercial growers of acid loving plants, with all the science behind them, use acidic soil mixes.
I stand by the idea that materials that are known to create acidic soil mixes absorb cations and release hydrogen ions.

Don't pot your rhododendron or azalea in pH inert gravel please.

For a long time I was under similar misunderstandings with regards to what is actually happening at the molecular level with soil components, their interaction with water, and the nature of Ph and its import role in plant cultivation. As has been demonstrated here its tricky and complex stuff to grasp, I'll be the first to admit I didn't do well in organic chemistry. But the Idea of how Ph works functionally is really chemistry 101 type stuff.

The book i referenced and the discussion we had with Paul really opened my eyes and allowed me to better understand how my trees grow and thus how to better care for them, Chris (coh) I believe had a similar revelation at the same time as we were both active contributors and interlocutors in the "Help with Beech leaves thread" I truly wish you may find similar understanding Glaucus.

I am certainly neither qualified nor willing to try to educate someone about soil science as I fear I might make a mistake. I'm just a Farmer not a botanist. Hence I referred you to an in-depth discussion right here on this forum and an outstanding horticultural text If your interested in further information on the subject.

I wish you the best with your trees!
-Jay

drgonzo wrote:The book i referenced and the discussion we had with Paul really opened my eyes and allowed me to better understand how my trees grow and thus how to better care for them, Chris (coh) I believe had a similar revelation at the same time as we were both active contributors and interlocutors in the "Help with Beech leaves thread" I truly wish you may find similar understanding Glaucus.
-Jay

Hey, don't drag me into this! Only kidding...but I don't claim to have had any real revelations yet. I don't really have an good grasp of the whole soil pH/water pH interaction but I'm keeping an open mind...and will probably be doing some experiments/measurements this growing season.

The main things I took away from the other discussion were (1) the possible value of using non urea-based fertilizers with our (mostly) soil-less mixtures, and (2) the possible (probable?) importance of water pH. I will definitely be evaluating and experimenting along these lines this year.

I have used both aluminum sulfate (seems to be quick and not long lasting) and granulated sulfur( lasts longer) to acidify non-organic soils. I now just dose the pots with acidified water if I notice PH related decline symptoms. I use "PH down" by Dynagrow and test it in a tank to get the right PH. Some growers use a injecter sytem. Professional green house operators in my area have soluable fertilizers that are designed and formulated to address their specific PH issues of there source water and plant type, some actually have multiple injectors to offer separate water sources with the special formula. When asked they say that eventually all soil will end up being the PH of whatever it is being watered with especially if there is frequent waterings. In my opinion this PH issue as it relates to non organic soils has been a significant issue with my garden. Soils with some organics seem to buffer the effect of high PH mineralized water like mine. If I use exclusively rain water I have far less problems and also RO systems don't do much to adjust the PH so often those that RO have to acid inject also.

Glaucus wrote: I think we can at least conclude that the mineral doesn't ionize the water as suggested

Actually its the ionization or de-ionization of water that is exactly what we measure when we measure pH. We measure the concentration of aqueous hydronium Ions. Thus pure de-ionized water is considered pH neutral.

To the best of my understanding; when the Kanuma in our hypothetical example enters solution the balance of H+ and OH- ions in the solution changes. Stated very simplistically the kanuma particle would attract free OH- ions leaving a greater concentration of H+ ions in the solution, thus the solution now is more acidic then it was before it came into contact with our kanuma particle. This is the process known as buffering. Hence when the kanuma is removed and time passes the water will revert to its previous ion balance. This is why the soil itself is not acidic only its effect on water is acidic. This is why soil strictly does not have a pH per-se it more accurately has a pH reaction. When we truly understand this concept we begin to understand how we can better grow our bonsai through manipulation of our liguid feed rather than manipulation of the soil mixture. This is ,as crust mentions, how many major nurseries operate with thier fertilization programs. It is an essential key to success if one is to use inorganic soil and inorganic (synthetic chemical) fertilizers.

It also explains why artists Like Harry Harrington in the UK and many others grow excellent Azaleas in a medium with a pH reaction of 7 -neutral. They simply alter the ph of the nutrient solutions they feed with. In fact most chemical fertilizers when mixed with water will, due to their own innate acidity (or more accurately buffering capacity), lower the solution pH into the acceptable range for many calcifuge plants including Azalea or Bougainvillea. Whats even more confusing is that "buffering capacity" is expressed in terms of alkalinity, a term which itself is often mistakenly confused with Basisity.

As I said I'm no expert but I felt I wanted to at least attempt to explain to the best of my understanding what I was talking about. I can see reading back that when I used terms like "liberates" and "releases" Hydrogen I should have been much more specific in my terminology these terms weren't as accurate as they could have been to explain what is happening with this process. Perhaps that was the source for some of our missunderstanding of each other. Thank you for giving me the opportunity to refresh my own understanding of this topic.

best
-Jay

I only just discovered this thread. It’s very interesting, though think some points are not clearly understood. I think getting you head around pH in pots is difficult as it is a dynamic system and there are many things which influence the pH all happening at once. I’ve been trying to think of a way of explaining how pH changes without writing a huge essay, but can’t do it. The reference to pH in growing media made by Jay is the most succinct treatise I know of.

But hopefully I can clear up some points without upsetting anyone.

pH is an attempt to measure hydrogen ions in water. By definition it is the amount of hydrogen ions dissolved in water, something that is “dry” has no pH. Pure water has by definition a pH of 7, this translates to it having about 0.0000001 ppm of hydrogen ions in it. This is an incredibly small amount of anything and is difficult to measure. If we consider the amount of sodium in water being high at 50 ppm we get an idea of how small 0.0000001 ppm is. So any pH measurement is a ballpark measure, just getting near is good enough, don’t sweat the decimal points.

When we dissolve a salt in water, some of the water molecules will dissociate into OH- and H+ , this due to the electric charges of the ions. Depending on whether the H+ or OH- remain “active” or not determines the pH of the solution. When we put potting mix in water some elements; say sodium, calcium, magnesium (even hydrogen ions) will dissolve in the water and affect the pH. The amount of water used in the test also affects the pH, (less water makes a more concentrated extract, more water less concentrated). That is why these tests have become standardized around the world, so that even though the pH is not the “real” pH of the potting mix that the plant experiences, everyone understands that the measured pH means something because they have standardized these test results with growing plants.

Components in potting mixes have many different salts in and on their surfaces, so that when the potting mix is placed in water the pH of the water will change depending on the salts present. How much it does this depends on the quantity of the salts on its surface, types, there solubility and how much H+ is absorbed onto the medium.

Buffing capacity is the ability of a potting material to absorb or release H+ to maintain a stable pH. A strongly buffered potting mix will require more acid to lower the pH than a weakly buffered potting mix. Akadama may be strongly buffered because it has a high cation exchange capacity, it can have a store of acidity in which to react with any alkali added to the mix. Or it may exchange sodium ions for hydrogen ions, removing H+ from the soil solution and preventing the pH from dropping. Quartz gravel has a very low cation exchange capacity and so is a very weak buffer, it has no H+ or other cations for exchange so it doesn’t take much for the pH to change when it is used in a potting mix. Even if its initial pH is 9 it doesn’t matter because it will soon be something else after the first watering. Adding limestone chunks may be a different story as it takes a lot of acid to neutralize it, it has a very high buffering capacity.

Buffering capacity is finite, it can be depleted (even limestone chunks can be dissolved eventually). A potting material may be acidic or alkali, but it may have a low buffering capacity and so that pH is negligible in the system. The point I am trying to make is that the pH of potting materials is finite and so will vary over time. It will vary quickly (in days) if it has low buffering capacity, slowly (only over a time scale of weeks) if it has high buffering capacity.

The amount of soil you can fit into a pot limits the amount of buffering capacity it has.

Different things affect the pH differently. Certainly the amount of carbon dioxide dissolved in the potting mix solution will affect pH, but it will be minimal to the affect a water that contains 100ppm of bicarbonate will have, which will be small compared to a fertilizer with 400ppm of ammonium. Many things affect pH, it’s the cumulative reactions that determines the overall pH.

The main drivers of pH in bonsai pots are the fertilizer you use, the plant itself, and the irrigation water. The buffering capacity or initial pH of the components is finite, while the addition of water and fertilizers and plant interactions is ongoing, and in comparison, infinite.

I hope this helps clear up some of the confusion,

Paul

add unsweetened lemon juice. I use this on my satsuki.

The main drivers of pH in bonsai pots are the fertilizer you use, the plant itself, and the irrigation water. The buffering capacity or initial pH of the components is finite, while the addition of water and fertilizers and plant interactions is ongoing, and in comparison, infinite.

Many thanks, Paul, for this and what preceded it. I hope that it clears things up for everyone. I'm gonna try to remember where this message is hidden, so we can refer people to it when this subject comes up NEXT -- and it will.

There's a lot of myth associated with bonsai.

Paul,

Thanks...I actually understood it LOL. Bookmarked!