How do we acidify inorganic Bonsai soil?

Thank You SO MUCH for showing up Paul.

And thank you again for all the help you gave me last summer It has literaly changed the way I do Bonsai!
-Jay

Thanks Paul! Your input on the other thread was also much appreciated.

I don't have the Argo book, but when the other thread was active I found a number of on-line articles that he wrote about the whole subject. I found them helpful, maybe others will as well. There are 5 articles titled "Understanding pH management and plant nutrition", and they can be found at this website.

The other thing I wanted to suggest - would it be possible to modify the title of Jay's other thread, Help With Beech Leaves...that thread evolved into a very interesting and useful discussion about water quality and fertilizer that people might not be able to find using the crude search function on this site. Maybe re-title it "Help With Beech Leaves, Fertilizer, Soil pH" or something like that?

Thanks for the positive responses, but while cleaning my teeth this morning I realized I made an error.

pH 7 may be converted to 0.0000001 g/l; but ppm is mg/l: so pH 7 is equivalent to 0.0001 ppm H+

The following is something I wrote to help clarify it all in my own head, so hopefully it will help people here understand the processes involved.

I think it’s better to think in moles, as chemist do, rather than mg/l as horticulturalists do, this is because it’s all simple ratios with moles. As an example we can work out how much acidity a plant can produce when taking up some ammonium fertiliser.

If we assume a plant can take up 10 mg of ammonium in a day (which is very doable). How much acidity will it release? That’s to hard in mg/l so lets convert over to moles. 10 mg NH4 is 0.56 mmol or 0.00056 moles of NH4.
Plants excrete one molecule of H+ for each molecule of NH4 they take up. So it’s a simple one to one exchange, so the plant will excrete 0.00056 mole of H+. If this is all in a litre of water, possible in a large bonsai pot, it will make a solution with a pH of 3.5 ((give or take a lot of fudging) since pH is the -log of 0.0056moles H+/l) If its is only 1/2 a litre of water the pH is even lower. So plants have a good capacity to lower the pH of the soil around it simply by taking up ammonium ions.



I’ve been wondering how to explain this for sometime and I think it may make more sense if we look at it from how a plant changes it environments pH, and this happens for several reasons.

Firstly the inside of a plant cell has as specific pH range in which they can function in, as well as a preferred electrical charge. So the insides are a little alkali and a little negatively charged. The cell also has special pumps in its membranes which move atoms in and out, some things can flow in quite freely,eg. potassium, nitrate; while some things need to be escorted, like iron, for instance, it needs a hydrogen ion to escort it across the membrane. Ions usually cause electrical imbalances across the membrane and so if a positive ion is taken in, a negative ion might travel in with it, keeping overall charge neutral, or a positive ion might be pumped out. Some things like ammonium, cause a pH imbalance in the cell and something has to be evicted to maintain this pH balance, with ammonium, it is hydrogen ions (acidity). Nitrate only needs the charged balance, so chloride might be evicted, or potassium might be taken up. The plant may also excrete bicarbonate, which will cause an increase in the external pH.

So, one ammonium molecule causes one hydrogen ion to be excreted from the cell. One nitrate ion may cause a number of things to happen, so maybe 3 nitrate ions causes one bicarbonate ion to be released. This is why ammonium is better at lowering pH soil pH then nitrate is at raising it.

What happens to the hydrogen ion that's been excreted?

The hydrogen ion that is now outside the root cell is a bit like a boat on a river without a paddle, it gets pushed and pulled about by the whims of electric forces and currents. So it might be dragged back into the cell as an escort for iron. It might drift out in the soil solution, where it will lower the pH. Once there it might exchange on the surface of a soil particle, raising the pH (this is buffering the soil solution). It may react with some lime, creating carbonate, and releasing calcium for the plant, raising the pH again. It might get washed out of the pot with some nitrate in the next watering and so leave the soil in the pot with a slightly higher pH. All hydrogen ions are busily being pushed about, sucked in and spat out, adsorbed, desorbed, neutralized, activated, all of the time. It is the cumulative addition of all these things which gives the pH of the soil solution, so the process is dynamic and can changed very quickly.

So this is how fertilizer lowers the pH of the soil, ammonium is taken up by the plant and pumps out hydrogen ions to maintain cellular pH, lowering the soil pH in the process. Nitrate in the fertilizer raises the pH as cells pump out bicarbonate to balance electrical charges in the cell. If your plant is taking up ammonium at a rate greater then nitrate, then the pH of the soil will drop, becoming more acid. If the plant is taking up nitrate and no ammonium, the pH will rise. This is not a hard and fast rule as different plants take up nutrients at differing rates depending on what there growth requirement is.

The fertilizer you use will affect the soil pH over a relatively short period of time. How much it affects the plants depends on the plant, its environment and the ration of NH4:NO3.

But wait, it gets more complicated!

Irrigation water affects soil pH by the amount of bicarbonate that is present in it. This is water alkalinity, not hardness. Water hardness refers only to how much calcium and magnesium is present relative to sodium. It does not affect pH. Alkalinity is different. Bicarbonate HCO3(-) is able to take up H(+) to form H2CO3, this occurs in acidic solutions, (neutralizing the acidity, raising pH) and can lose a H(+) to form CO3 (2-)lowering pH. Its acts like a buffer, but it is an alkaline one by nature and so pushed pH up as its concentration increases. {I’ve put the electrical charges in brackets just to simplify the molecular formula}

Bicarbonate tends to raise the pH , the more the bicarbonate in the water, the higher the pH, this is because it removes some of the H+ from water molecules to form H2C03 and OH- (alkalinity)

When we water our plants, we wash out a whole lot of stuff and add some new stuff from the water. I’ll simplify it to only a few things, but it’s the basis for how pH rises. Bicarbonate always has a partner, it might be calcium or sodium or some other +ve ion, it always has a positively charged ion with it.

When we add bicarbonate to a bonsai pot, it will react with a certain amount of acidity (making it inactive) and raising the pH slightly. It takes a lot of bicarbonate to deactivate a little bit of acidity, it’s not a one to one reaction, more like a 100 to one. The soil particles in the bonsai pot might have a little buffering capacity. In this case, the +ve ion that travels with bicarbonate has been dumped for hydrogen ion, and so, dejected and feeling miserable, lounges next to a soil particle (think Bar) and pushes the guy in front of him (wimp!) out of the way (hydrogen ion) so he can get a beer and drown his sorrows. The displaced wimp, I mean hydrogen ion, gets offended and leaves the bar, the overall pH of the soil solution remains the same, but the buffering capacity has been reduced. We water again, the original bicarbonate and its new hydrogen ion partner is lost by leaching, and another bicarbonate ion/+ ve ion couple comes to replace the one washed out, again it reacts with a hydrogen atom (probably the wimp) and the +ve ion exchanges with another wimp on a soil particle. Repeat every day.

After awhile all the exchangeable hydrogen ions will have been removed from the soil particles, but more bicarbonate keep coming. As the soil dries out (transpiration evaporation) the concentration of bicarbonate increases and pH rises. We water again, more bicarbonate, more pH rising, no hydrogen ions to buffer it. Soon the soils pH raises and eventually becomes too high for happy plant growth.
So what do we do?

We can lower the water pH by adding acid, this forms H2CO3, not a real problem, but to convert all the HCO3 to H2CO3 we have to push the pH down to about 4, which is too low for plants. If we push it down to 6, then there will be some HCO3 remaining to push up the pH, not a real good solution.

We can add acidifiers to the soil things like iron sulfate or alum, which react with water and cause acidity, neutralizing the affect of the bicarbonate. Until you water again the next day, unfortunately the effect is short lived.

We can add something like sulfur, which creates acidity over a period of time keeping the pH down. That’s OK, until it goes too low and you can’t get it out of the potting mix. It’s an OK mns of keeping pH down and is used in agriculture a lot as a means of adjusting soil pH.

We can feed the plant ammonium, to use the plants own Hydrogen ion pump to lower soil pH. This works well as long as you do it often enough.

Unfortunately there is no simple solution, but each nursery has to develop its own system for balancing pH depending on the plant and the water it uses.

What seems to work is reduce the pH to an acceptable level using something like iron sulfate, and then balancing the ammonium to nitrate ration in a fertilizer solution and monitoring the pH of the plants. It is possible to get stable pH in an acceptable range by juggling the ammonium and nitrate levels in a fertilizer solution. The higher the bicarbonate levels, the more frequently you have to add ammonium. Usually for levels like 200 ppm bicarbonate you would be feeding the plant with ammonium every day.

Using miracid once a month or so is pretty much the same thing as above. If you have a small bicarbonate problem, it might take a few weeks for the pH to rise enough to cause problems, a big dose of miracid injects a lot of ammonium into the potting mix and plants excrete acidity as they take up ammonium, balancing the pH.

I hope this help to make the process clearer.

Paul

63pmp wrote:Thanks for the positive responses, but while cleaning my teeth this morning I realized I made an error.

pH 7 may be converted to 0.0000001 g/l; but ppm is mg/l: so pH 7 is equivalent to 0.0001 ppm H+

I'm so glad you got that fixed. While flossing this morning, I could barely concentrate as the miscalculation was bugging me so bad ...
(joking--I wouldn't have caught that miscalc in a million years)

How could I have known that this bonsai forum would make me laugh almost as often as the high school students I teach? Visualizing a man (who I'll refer to as Paul) brushing his teeth while rehashing somewhat complex PH calculations is a funny sight in my minds eye. I have a couple of friends that are electrical engineers and that is how their brains work. Math equations all the time with no ability to ever switch it to the 'off' mode. But seriously, I have learned a ton reading this thread. Thanks to those who have contributed such great, technical information.

Using miracid once a month or so is pretty much the same thing as above.

So what is it about miracid that is actually "acidifying"? Is it that the solution itself is acidic, or is it the effect that it has on the plant roots (causing them to excrete H+)?

I had taken samples of 2 fertilizer solutions (miracid and Peters 20-20-20) into a hydroponic shop for pH testing. Surprisingly (to me), they tested quite similar. That leads me to believe (assuming the instrumentation was working properly) that the acidifying effect of miracid is through the ammonium-uptake mechanism Paul described.

However...miracid (30-10-10) lists only 3% ammoniacal nitrogen (and 27% urea). Dyna-gro 7-9-5 has almost the same % of ammoniacal nitrogren (2.6%) but no urea, the other component is nitrate 4.4%.

So how does one determine if a fertilizer is acidifying - and to what extent? Is the urea converted to ammoniacal nitrogren? Does the presence of the nitrate effectively negate the NH4 (in the dyna-gro, for example)? Do the amounts (and types) of the other components play a significant role?

Maybe it's time to ask the question: "Why do some plants need more acidic conditions?"
I believe it largly has to do with the availability of iron. Iron is more available (soluble) in acidic solutions. It takes an insoluble (unavailable) form under alkaline conditions. Some species can cope with this better than others. Insufficient iron can interfere with chlorophyl production, resulting in chlorosis. Miracid may not be expecially acidic, but it has iron in a chelated form that stays in solution and is available even under conditions that are not especially acidic.
Oliver

Chris and Oliver...

I feel I might be able to answer both your questions regarding Mir-acid and Iron with sufficiency, but when Paul shows up in one of these threads I just sit back and learn....

-Jay

Come on Jay, give it a shot! Paul is in Australia, who knows when he'll log on again!

I've been reading through the articles I posted...seem to have answered some of my own questions. As Paul states...NH4 uptake leads to acidification (plant root releases H+), NO3 uptake leads to "basification" (pH increase due to plant excreting bases). Urea is converted to NH4, whose uptake will lead to acidification. But there's another process that can work - nitrification, whereby the NH4 is converted in the substrate to NO3. This process releases H+ and acidifes the substrate. This appears (to me) to be the way that miracid "acidifies". Am I correct here? (Edit...after re-reading the "beech leaf" thread...this seems to be a reasonably accurate description of how miracid acidifies. There's a lot of great info in that thread)

As for the impact of pH...according to the articles, there are several elements whose availability can be influenced by pH...iron for sure, but also phosphorus, manganese, zinc.

coh wrote: Urea is converted to NH4, whose uptake will lead to acidification.

As for the impact of pH...according to the articles, there are several elements whose availability can be influenced by pH...iron for sure, but also phosphorus, manganese, zinc.

Ok if you insist, but I hold the right to be totally wrong without aspersion if Paul steps in and corrects me

Yes Chris my understanding of Mir-acids effect is that the plants roots respond by releasing H+, thus the water immediately surrounding the roots acidifies and nutrient uptake is enhanced. Plants respond in similar fashion for many other elements as well, its amazing when you think about how complex and clever plants really are. How they have evolved to do what they need to to get what they want.

Iron is very sensitive to pH range, some plants are able to absorb iron better throughout a larger range of pH and are called Iron efficient plants, my Geranium is a great example. Other plants not so much. Hence my poor Beech last year with his iron induced chlorosis. There are also interactions with Iron that happen on the surface of the soil particles when they come into contact with iron that can limit the availability for root absorption. This is part of why chelation is so important for keeping trace elements in solution long enough for the plant to get a sufficient dose.

here's a cool little web page about chelation if your interested, nice easy read.
http://www.sperchemical.com/html/chelation_of_minerals.html

-Jay

"So how does one determine if a fertilizer is acidifying - and to what extent? Is the urea converted to ammoniacal nitrogren? Does the presence of the nitrate effectively negate the NH4 (in the dyna-gro, for example)? Do the amounts (and types) of the other components play a significant role?"

Yes, that is pretty much it. Urea is converted to ammonia by bacteria in the potting mix. Then, when the ammonium is taken up by plants (or other bacteria) they release H+ to balance cellular pH, acidifying the soil.

One urea molecule produces 2 ammonium molecules. Urea is not only pH nuetral, it is not detectable by EC tests, so it adds to salinity, but is not measureable (it is non valent ie. no elctrical charge as it's an organic molecule)

With fertilizer, it is the ratio of Ammonium:Nitrate (NH4:NO3), that influences the pH .However, we have to also consider the alkalinity (bicarbonate content) of the water and the plant, and so NH4:NO3 has to change to accomodate that. Each species of plant grows differently, some picea for instance don't particularly like NO3 as a source for N. So for some picea, you may have to keep NH4 at very low concentrations relative to NO3 to keep the plant from selectvely feeding on NH4 and acidifying the soil too much. So you have to monitor your plants carefully and see how they're growing, they all behave differently.

Urea has some problems as a fertilizer, in that it requires bacteria to convert it to ammonia. This requires oxygen to be present as these bacteria are strict aerobes. A different bacteria is required to convert ammonium to nitrate, and these go on strike at temperatures below 16 C. So its possible for the potting mix to become too acidic if the irrigation water has low alkalinity and you apply urea regularly. Also plants like azalea are susceptible to ammonium toxicity, so they might suffer a bit with a build of ammonium. Urea is not bound to the soil so its easily flushed/leached out, and it takes time for the bactea to convert it and release it back into the potting mix, which might be an issue.

Urea fetilizers are cheap to make, and mostly a designed for use on lawns and garden beds, as the soil has a high enough buffering capacity to take up the ammoium and the pH changes. It thinks it is a bit to variable to controlin a bonsai environment. Thoiugh I know plenty ofpeople use it and like it. Maybe I'm too much of a control freak.


My understanding with iron uptake is that iron must be co-transported across the cell membrane with a molcule of H+.

Some plants (those that tolerate high pH) have the ability to pump H+ out of the roots regardless of the presence of ammonium. Pelrgoniums are an example. Other plants, azalea, petunia's, and J. maple are not so good at this and so at higher pH's there is a shortage of H+ at the cell membrane, these plants then cannot take up enough iron as they lack H+ to transport the iron into the cell. On the down side, those plants that pump out H+ in alkali conditions, eg. pelargoniums, can't turn it off in acidic conditions and so poison themselves with too much iron.

Iron also forms tough to crack complexes at higher pH's, yes, but I think it is the low H+ concentration at the cellular membrane which stops iron transport as being the main problem.

Regards

Paul

Paul

Knowing now that its the release of H+ by the plant in reaction to the ammonium by product of microbial action on Urea, Being how products like Mir-acid work;
How do you think our Urea free fertilizers (with 8%Ammoniacal Nitrogen and 12%Nitrate as their nitrogen source for example) will fare when used with plants like Azalea. I know My Bougainvillea's have a low pH preference and they seem to love the Urea free.

how Would the 8%NH4:12%NH3 effect soil water pH? Assuming de-ionized irrigation water is used to keep things simple. I'm wondering how my Urea free fertilizers will do with Maples, Azalea, Beeches..etc this upcoming summer as I have yet to try them on my deciduous trees.

Always glad to have you answering and educating us!

-Jay

Thanks to everyone contributing for such a great discussion. The complexity is high but it explains many things I have wondered about over the years. Water issues and plant nutrition are fascinating to me.

This is excelent - but with hindesight I'm wondering if we are getting a little too westernised with the thinking and missing some undeniable result driven facts..

Basically a vast majority of the finest OLD bonsai reside in a number of japanese nurseries, and have done so for many decades, passing from generation to generation. When we see them at shows, calenders, in apprentice books and blogs etc they are in perfect health and awesome condition - the bark gets more aged and the foliage remains fresh. The trees are basically potted in a combination of akadama, kiryu, kanuma, long grain moss and river sand - the ratios being changed for the tree species. The feeding from that point (we are lead to believe) is very similar recipe cakes for most trees, just the amounts, timing and frequency are varied. In Cornwall we get periods of high rainfall at times so I use additional chealated iron as a soil additive, and do soak the one azaelia in a miracid bath 2 or 3 times a year.

This suggests 2 avenues - adapt the actual soil to the trees' needs and feed a balanced fertilizer, or stick to a soil made from one single neutral composite and continually acidify with added products. The test of time is a great decider - at the moment one method is undeniably proven and one is in its infancy. My personal path as several know is to rely on 'traditional' japanese soil components and I see superb mychorrhizal fungi growth throughout many pots (this is what really keeps the trees in perfect health afterall, not the fertilizer). I will watch with interest the single soil users to see if they get various species of this fungi colonise the potting medium as this is a major key to keeping mature bonsai.

Great thread, one to remember for the future for sure, but I feel the need to take one step back and ask yourself why you actually want to use a single component soil in the first place needs answering before worrying about the added complication of acidifying it.

cheers, its threads like this that make ibc top of the pile for me.

Marcus

I think a lot of the reason the Japanese use the soil they do is because modern substrates are just that...Modern. Tradition is a strong cultural influence for the Japanese. The prevalence of organic fertilizers in Japanese Bonsai would also require organic matter in the bonsai mix, I believe it helps foster the soil bacteria that make the organic fertilizers available to the plant through metabolic action. I note in Peter Adams book his mention several times of the soil mix used at Fukukaen of Nagoya containing 1/3 organic. He himself recomends 40-60% for Maples

With increasingly efficient modern synthetic fertilizers the option to use a purely inorganic media becomes available, due to the soil microbial activity being unnecessary for modern fertilizers like my Urea Free and chelated minors. I switched after getting Verticilium wilt on a maple I liked quite a bit, as I was able to reasonably pinpoint the source of the oospore as being the pine bark I was sifting from soil bags. I then started reading about and indeed contacted Harry Harrington about his great success with pure inorganics.

Since then whatever I have been planted in 100% Turface has just exploded! Far out growing other plants that still remain in my old mix. Its difficult to over water, its difficult to over fertilize, the medium cannot compact or break down, and issues like root rots become almost moot. The soil aeration and resulting root activity is phenomenal. It also makes re-potting time so much easier. These mediums have been known to horticulturalists and time tested in hydro-and aeroponic gardening for decades, it is perhaps only the weight of tradition that has kept them out of Bonsai culture for so long.

Mychorrhizal fungal activity and its necessity for plants is still being investigated. Some feel with fertilizers that are very efficient at delivering their nutriment, the fungal activity becomes much less important, and that explanation certainly appeals to my common sense.

The choice of soil and fertilizer go hand in hand in my opinion. A change in one may, or may not, require altering the other and vise versa..

But Marcus after seeing your trees and especially your Kaho Azalea I say 'If you have a system that has worked that well for you, don't change it..'

This thread and the 'help with beech leaves' thread have taught me more about Bonsai than anything else on IBC yet!!
-Jay

I don't want to turn this into a debate or argument about which approach is "right" or better. Valid arguments can be made for both. I will say, however, that it should be kept in mind that the techniques developed over the years in Japan may not translate directly to other locations for a variety of reasons...climate and water quality being the primary ones. My other concern would be the reliance on materials that must be shipped from halfway around the world. Besides cost, what do you do if that supply runs out or becomes difficult to obtain?

The main benefit I see to this discussion is that it gives individuals the information required to make informed decisions for themselves. For example, the often repeated suggestions to "fertilize with miracid" (or other "acid" fertilizer), or "apply extra trace elements" may not always work as expected, depending on the soil components and water quality being used. Understanding the information being discussed here can help one figure out how to proceed when the usual methods don't succeed.

At least, I hope that's the case! I know I've been dealing with problems with a few plants the past couple of years...we'll see if this info helps me figure out what I'm doing wrong...

Thumbs up for this thread and I love the last three posts for maintaining a great tone and feel while making valid and key points to the discussion.

Jesse wrote: I love the last three posts for maintaining a great tone and feel while making valid and key points to the discussion.

Its only natural as I have great respect for the members on either side of my most recent post, the search for knowledge is always made easier with humility.

How do you think our Urea free fertilizers (with 8%Ammoniacal Nitrogen and 12%Nitrate as their nitrogen source for example) will fare when used with plants like Azalea.

I use a urea free chemical fertilizer that I blend myself to feed azalea, japanese maple, J. Beech. They seem to do very well with it.Urea is not a natural planyt food, sure its excreted by mammals all around the world, but its very quickly broken down to ammonium by bacteria, plants in the wild never feed off the stuff.

how Would the 8%NH4:12%NH3 effect soil water pH? Assuming de-ionized irrigation water is used to keep things simple. I'm wondering how my Urea free fertilizers will do with Maples, Azalea, Beeches..etc this upcoming summer as I have yet to try them on my deciduous trees

Regarding soil pH and your fertilizer, it’s hard to predict where it will go. You will just have to watch your plants and see what happens. Japanese maples are a good test plant to have though, as elevated pH really affects their leaves. Beech just stop growing and azaleas go yellow. Just keep a close eye on them. Test the soil pH after 3 weeks or so, if you like, to see if it’s drifting. But visual inspection of your plants is a good option. I don’t like digging about their roots too much, maybe once or twice to just confirm a suspicion.

Two most important aspects of fertilizing with chemical fert for these kinds of trees is to keep the EC low, around 700-1000 micro seimens/cm. The other is not to feed them until about 3-4 weeks after they bud out. I suspect maples (maybe beech) are very susceptible to ammonium toxicity early in spring, certainly the Japanese practice this approach.

I also believe that a lot of leaf damage we see in summer and call windburn is a result of poor feeding in spring when leaves are developing. If something nutritional is not available (or excessive), or imbalanced, as the leaf is developing, then the quality of the leaf suffers and has less resistance to summer stresses. I’ve seen this happen this year with maple leaves that grew when soil pH was too high, these leaves showed much lower tolerance to diseases, sun scorch and marginal leaf burn etc, leaves that grew once pH was returned to normal were much more tolerant. Just my observations, so take it with a grain of salt. The thing for me to do now is to show there is some reality to the observation.

Regarding the Japanese and there horticultural practices. I personally believe we have a lot to learn from the Japanese on looking after plants, I’m certainly not saying we should not listen to them. All I have been talking about is plant physiology, how you feed the plants is up to you. Bear in mind that every person doing bonsai will have a preference for a fertilizer and a soil that suites them, and may not suite others. If what you are doing works for you then great, keep at it.

I think fertilizer balls are an excellent way to feed plants, I’m a firm believer that continuous feeding with frequent flushing of the root ball is the way to maintain healthy, vigorous growth. I only use chemical fertilizer as it is cheap and convenient. But I have no problems with organic mixes or fertilizer balls. I also think the way Japanese feed is important as well, in that they feed a little in spring, a little bit more in summer, and more in autumn. I’ve recently been reading about how deciduous trees store nitrate in their roots during autumn for spring growth, and recent home research has shown to me that trident maples do not need any fertilizer in the first three or four weeks of growth. Last year I fed my trees with nitrate up until they dropped their leaves and I was impressed with the number of dormant buds that developed into shoots this year. I don’t think plants care how they get their nutrients, just that they are there, it it seems important that nitrate be present in autumn. This is of course, the complete opposite to what many say should be done. Apparently this is what deciduous trees do, they store nitrate over winter for spring growth. WHY? Probably because ground temps are too low for nitrification in spring. The only N available is ammonium. Ammonium requires plant carbohydrates to de-toxicify it when it is taken up ( and at a time when plant carbohydrates may be depleted). If plants store nitrate over winter (taking it up in autumn when it’s plentiful) they don’t have to take up any N in spring, they can get leaves out and be producing carbohydrates, ready for when they do require soil ammonium. This is why I say don’t fertilize maples in the first three weeks of growth in spring.

The important thing for plants is that ALL elements needed for growth are present, and not many fertilizers supply them all.

As for substrates, they must provide appropriate levels of oxygen to the roots, water holding capacity is important, but it is the air filled porosity that is critical for good plant growth, and disease resistance. What they are made of is important, but particle size is probably most important. I think having your soil near a pH that is good for growth is a good policy. Especially for any plant that is not going to be fertilized for a while, pH will only change when plants are taking up nutrients, water may push it up if it has some alkalinity, but repotted plants that are not being fertilized will recover better if the new soil mix is at the appropriate pH.

Potting mix contaminated with disease is a big problem everywhere, an article in the Australian IPPS newsletter by a manager of a company that produces a large proportion of potting mix here, clearly states that pythium phytophthora, fusarium and other major plant pathogens are all endemic in potting mixes. Nearly all these fungi need low oxygen levels to gain access to plant roots. If you can maintain high air filled porosity then soil borne diseases shouldn’t be a problem, of course this means repotting at the appropriate time, keeping pots elevated to maintain excellent air flow, etc etc

This suggests 2 avenues - adapt the actual soil to the trees' needs and feed a balanced fertilizer, or stick to a soil made from one single neutral composite and continually acidify with added products.

Its not the soil that changes the soil pH, its the plant, the fertiliser an the irrigation water combined together. If the fertiliser has no ammonium and all nitrate then the soil pH will drift up, no matter what its composition, no matter what the source of the nitrate, whether organic or mineral. Organic fertilisers have less problems because most of the N is in organic complexes, there is a natural buffering effect, but it can still cause pH's to drift, or may not provide enough acidity to counter water alkalinity, if there is any.

Also, the Japanese still have their problems with plant health. There are many articles in Bonsai Today dealing with sick and unhealthy trees, root rot, salinity etc. I’m not sure how you adapt a soil to the trees needs in a pot. This is an ongoing problem, and even the Japanese have changed their soil usage over the years. Old bonsai books from the sixties suggested a certain type of ground soil was best for bonsai, now it is all akadama and kunama. What I suggest is doing simple pot trials in your own yard to see what works best for your trees in your environment.

What’s a balanced fertilizer? Would the same fertilizer be suitable to use on a JBP and a J maple?

I use only chemical fertilizer, some of my pines have a lot of mycorrhiza, others hardly have any, I can’t tell which trees have mycorrhiza from those that haven’t without looking at the root ball. Some scientific research shows there are benefits in early germination, higher germination rates, earlier recovery from transplanting, higher tolerance to drought; with using mycorrhiza. What seems to be very important is getting the right type of fungi for that particular species of plant.

I seem to have rambled on a bit here, so I'm going to call it a night. I’m really enjoying this discussion. There is so much to learn about how plants grow and we are only scratching the surface. And to think, science really only knows 3/5’s of bugger all about how they work anyway. We still don’t know how they take up magnesium!

Regards

Paul

What you may have gathered from all this is that if you have acid or alkaline soil, it tends to want to stay that way. Attempts to change it are fairly short lived.

It's not hard to find plants that thrive on neutral to acid soils, but there are plants that do well in alkaline soils, too. Here's a list to help you just live with it, derived from several I'net sources:

Here are some of the garden plants that prefer alkaline soil:

Evergreen shrubs
Green Velvet boxwood - Buxus ‘Green Velvet’ -- a cross between B. semipervirens and B microphylla; (Zones 6–8)
Daphniphyllum himalaense ssp. macropodum (Zones 7–8)
Photinia species (Zones 7–9)
Aucuba species (Zones 7–10)
Euonymus fortunei ‘Emerald Gaity’, ‘Silver Queen’, ‘Emerald n Gold’ (Zones 5–8)
California lilacs (Ceanothus spp.; generally Zones 8–10)

Deciduous shrubs
Daphne species (Zones 5–8)
Deutzia spp. (generally Zones 6–8)
Forsythia spp. (generally Zones 6–9)
Mock oranges (Philadelphus spp.; generally zones 5–9)
Lilacs (Syringa spp.; generally Zones 5–9)
Weigela spp. (generally Zones 5–9)
Spiraea spp. (Zones 3–8)

Perennials
Hellebores (Zones 4–8)
Pinks (Dianthus spp.; generally Zones 4–10)
Brunnera macrophylla ‘Jack Frost’ and ‘Looking Glass’ (Zones 4–8)
Clematis spp. (generally Zones 3–8)
Potentilla spp. (generally Zones 5–8)
Scabiosa spp. (generally Zones 5–9)

Trees
A tree is a woody plant with a main trunk and often a distinctive crown. Trees are also perennial, in that they survive longer than two years. The following trees thrive in alkaline soil:
Cedar elm (Ulmus crassifolia)
Holly/Holm oak (Quercus ilex)
Olive tree (Olea europaea)
Japanese plum (Eriobotrya japonica)
Asian persimmon (Diospyros kaki)

Shrubs
Shrubs are plants with woody stems but with relatively low overall height. Like trees, shrubs are also perennial. Many types of shrubs grow well in alkaline soil, including:
Japanese quince (Chaenomeles japonica)
Littleleaf boxwood (Buxus microphylla)
Feathery cassia (Cassia artemisioides)
Daphniphyllum (Daphniphyllum humile)
Silverthorn (Elaeagnus pungens)
Heather (Erica melanthera)
Cassina (Ilex vomitoria)
Lavender (Lavandula officinalis)

Vines
A vine is a plant with weak stems that supports itself by creeping, climbing or twining along a surface. The following vines thrive in alkaline soil:
Japanese honeysuckle (Lonicera halliana)
Chilean jasmine (Mandevilla suaveolens)
Bluebell creeper (Sollya heterophylla)
Common bean (Phaseolus)

Herbs
Herbaceous plants, more commonly known as "herbs," are plants with non-wood stems that die back into the ground each winter. Herbs can be annual, biennial or perennial. Several types of herbs need alkaline soil to grow, including:
Persian rockcress (Aethionema cordifolium)
Japanese anemone (Anemone japonica)
Kenilworth ivy (Cymbalaria muralis)
Baby's Breath (Gypsophila elegans)
Goldencup/Mexican Tulip Poppy (Hunnemannia fumariifolia)
Sweet Pea (Lathyrus odoratus)


There likely are others.

coh wrote: My other concern would be the reliance on materials that must be shipped from halfway around the world.

Hi Coh, there will be no arguments on a thread as good as this as everyone is adding their varied experiences and actual observations into the mixing pot to share knowledge. To be fair 'airmile reduction' just doesnt work with a hobby like bonsai though - it is a hobby relying on lots of goods being transported around the world as an awefull amount of the trees come from china, japan, taiwan, singapore etc, so do all the tools and accessories, lots of fertilizer, books, soils etc. (To participate in this hobby we all create airmiles and/or sea/road miles for our own personal pleasure).

you may find the climates across the United States are requiring a new approach to pot soils as the land mass is so huge, but I know a significant percentage of the good trees in the Uk are in soils with a lot of japanese components so something is working well in our climate. I did ask earlier what this stuff you guys are using is sold as in the Uk but not seen an answer yet - its not a cat litter type product is it ? as that gets very mixed results here - young trees and basic material seems ok in it but a lot of better trees seemed to loose vigour and refinement. I found on two trees that came to me in it the root pads were weak and poor after a further year on my benches so something wasnt working right for me.

I cant see that cost makes any relevant difference - in the UK the average soil ingredient cost is basically £1 per liter - a few components are a little cheaper but calling it £1 is close enough. 80% of my trees will remain in the pot for 5-10 years and a repot on most of them uses between 5 - 10 litres of displaced soil at most. The tree values are 100's of times the soil costs, and these days i sieve out the used soil and use it for normal garden container potting, then it goes on the borders so is returned to mother earth anyway so i'm only borrowing it really.

I personally think world trade is a good thing, it shares culture, experiences and keeps many countries, businesses and individuals solvent - shipping and delivery is just one small part of this essential network and I would say every one of us should go out of our way to buy from other countries to keep the flow of global wealth circulating. (especially coral and tropical marine fish feeds, bait for carp fishing and quite soon a range of modern organic fertilisers !!!! haha )

Hi again Jay - I applaud the thread and the incredibly knowledgable posts that are turning it into a real gem. Cheers on the kaho - it does seem to like me but one critical observation I have made over the years with azaleas is the micro fine roots seem happier penetrating the soil medium rather than growing around the particles so i think kanuma has an additional property that helps build the perfect root pad hence adding it to my acer mixes this season as an experiment. Re kaho - This year I have removed about 2/3 of the flower buds already as this is repot year and the tree mustn't be allowed to flower quite that strongly when it needs a proper root pruning.

You sound like you are getting excelent results Jay which is great, a lot of people will benefit massively from the soil change, and i think a lot more is going to be learnt about fertilizing over the next few seasons - and the real skills and learning will come from perfecting fertilising to slow and refine the growth on maturing trees rather than pushing it hard on developing ones. Good times ahead i think

cheers everyone

Marcus

just had a little play about to satisfy my curiosity

Marcus

The idea of Azalea wanting to "push" its roots into a medium has me further considering chopped sphagnum in the mix. All the re-pots so far this year including that Crenata are receiving sphagnum.

Interesting to note the akadama's pH in your test is the same as Turface which is what I use primarily its a high fired ceramic clay. Harry Harrington uses Tescos Low Dust Lightweight cat litter and seemingly has great results, it would seem to be another high fired clay product. I do believe there are a lot of unsuitable cat litters but Thats the one he uses for what its worth. I believe you folks have a product called seramis which is similar to my Turface.

My Azalea will have its re-pot next year, I have to let it flower so Russell can tell me its not a Kirume.
-Jay

If you want soil ph to be more basic ( alkline) all you have to do is go the way of Pa..

Just ad lime stone. takes the acid right out of everything and drops the ph... all water here for a result is not neutral... so i have to give the acid lovers more acid then what you would.

marcus watts wrote:I did ask earlier what this stuff you guys are using is sold as in the Uk but not seen an answer yet - its not a cat litter type product is it ? as that gets very mixed results here - young trees and basic material seems ok in it but a lot of better trees seemed to loose vigour and refinement. I found on two trees that came to me in it the root pads were weak and poor after a further year on my benches so something wasnt working right for me.

Marcus,

I've read on various forums about some types of "cat litter" that are available in Europe - supposedly they are fired clay products very much like the turface that we are using (see the reference Jay made to Harry Harrington), i.e. very hard, absorbent material that holds up well to freezing. But since I haven't seen these materials, I can't do a direct comparison. I've never seen a "cat litter" here in the U.S. that seems suitable. However, I'm aware of at least one well known/successful growers who has been using primarily turface (with a small amount of granite grit and peat) for many years with great results, so it can work...maybe not for all trees (azaleas, perhaps?).