pH: is it relevant?

Gustavo Martins · May 16, 2017

Hey,

I've been reading some people complaining about their water pH and how a high or low pH can affect plant growth.

Given my background in biological sciences, I have a slightly diverging view about the relative importance of pH in the water we use to water our plants. Let's see if I can make myself understood.

Osmotic shock:
Plants uptake water via their roots via a process called osmosis. The function of this process is dependent upon the amount of Total Dissolved Solids (TDS) in the water.

The catch, as it relates to this discussion, is that any action that changes the pH of the water is generally a result of the change in TDS. Hard water generally has high TDS levels, high pH, high KH, and high GH. Soft water generally is low in TDS, a low pH, KH, and GH. The occurrence of a pH rise (or decline) is generally accompanied by an increase (or decrease) in TDS. It is this change in TDS and the resulting change in osmotic pressure that impacts our plants. The problem is not a shift in pH to the pH in itself; it's the TDS: hard water vs soft water.

Note: I'm not talking about extreme pH (or pOH) levels, of course. These would burn the plants immediately. Hell, they would burn our hands too.

pH effects on other substances:
pH has an effect on the toxicity of ammonia. At a lower pH, ammonia is converted into ammonium, which is not toxic. As the pH increases, ammonium is converted into ammonia, which is toxic (at least to animals, not sure for plants). What is less known is that pH has the same effect on other toxic substances such as chromium, mercury, copper, and iron.

As the pH falls (solution becomes more acidic) many insoluble substances become more soluble and thus available for absorption. For example, 4 mg/L of iron would not present a toxic effect at a pH of 4.8. However, as little as 0.9 mg/L of iron at a pH of 5.5 can cause fish to die. (again, I'm not sure how important this is for plants).

So, It is not the the pH itself that causes issues. It is the physiological effects associated with TDS and/or the synergistic effects of pH increases, or decreases, on toxic compounds within the water.

How does this affect us?
Plants have evolved to use rain as main source of watering. Rainwater is often low in TDS (all salts are removed during evaporation). It is thus a soft water (regardless of its pH). Compared to this, roots are hypertonic and so water can enter the roots via osmosis without any problems. People leaving in areas with soft water should have, generally, no problems regarding this issue (note that the substrate can change this but since most people are using free-draining inorganics soils, this should be no problem). However, there are people that live in areas with hard water. Using vinegar (or other acid) is going to change pH (to some extent) but not TDS. So I am pretty sure this is not going to have any direct effect on plant growth (although it can indirectly if it does affect the toxicity of some substances - I am yet to study this regarding plants).

The only solution for those of use living in hard water areas is to use soft water (collected rainwater) or remove salts from tap water (via reverse osmosis). Any other solution that does not address the excess of salts (TDS) is only affecting pH and has little influence on osmosis, hence how plants absorb water.

Related to this:
This is also the reason why too much fertilization can "burn" the roots. As the concentration of ferts build up in the soil, so does TDS. When we water, this water absorbs the salts in the soil and becomes hard water. Above a certain threshold, the water around the roots may become hypertonic relative to the roots so that osmosis occurs the other way around: from the roots to the soil. Plants cannot absorb water and "burn". This effect should be minimal with the use of well-draining inorganic soils as excess of ferts are removed by watering and thus preventing the build up of TDS.

Does this make any sense to you? I'd like to hear from you on this...

Stickroot · May 16, 2017

I have very basic well water and it tests around 9! So yes I do go through about a gallon of General Hydro acid a year bringing it down.
I have noticed the biggest difference in cutting, more acidic water roots them faster.

Waltron · May 16, 2017

Could It Be Your Water?

by Jack Wikle

There is no need to read farther --- unless you are curious --- if you are one of those people whose bonsai consistently look healthy and grow well. On the other hand, reading more could be helpful if your trees fail to thrive in spite of your conscious effort to follow some old but good advice: water thoroughly and leach frequently to keep unwanted salts from accumulating in your bonsai soil. This is especially true if you keep seeing the common symptoms of what horticultural scientists know as low quality water: persistently weak green or yellow-green leaves with darker green veins often accompanied by scorched-looking leaf tips and burned leaf margins (most prominent toward the leaf’s tip).

By definition, “pure water” is nothing but water. But, being the “universal solvent,” water available to us from lakes, waterways, wells, the local Water Department or even a rain barrel is never pure. Actually, the “load” of dissolved minerals and other substances found in water – even water acceptable for use in human consumption and plant irrigation -- is highly variable.

People dealing regularly with water quality commonly make a distinction between “surface water” and “ground water.” Surface water is the runoff of rain into ponds, lakes and rivers. Ground water,” is water which typically has seeped deep into the ground through many tons of soil and rock before emerging as spring water or before being pumped back to the earth’s surface from a well. The reason for this classification is that surface water is relatively “soft,” that is, low in dissolved mineral content. Ground water, on the other hand, having accumulated lots of dissolved minerals as it settled deep into the earth is “hard,” i.e., high in mineral content. Where available, surface water is almost always superior to ground water for plant irrigation purposes.

However, we need to be aware that knowing your city’s water source is a river or reservoir does not necessarily mean it will be as low in pH and mineral content as one might expect. We are told it is not uncommon for municipalities to add chemicals, typically calcium hydroxide, to surface water in order to raise its pH (make it less acid) as a way of minimizing corrosion of public and private plumbing. These additives make water less satisfactory for plant use.

Technical publications directed to commercial growers of irrigated greenhouse and nursery crops make it very clear that water quality is a major factor in their success or failure. The standard recommendation is that a comprehensive horticultural water analysis should be done before settling on a growing site. Tables specifying recommended ranges for alkalinity, pH (not the same as alkalinity), soluble salts (usually measured by electrical conductivity), and six or seven specific elements can also be found in this literature. It is relatively common today for commercial growers stuck with low quality water to inject acid into it to make it better for plant use; even though this adds significantly to their production costs.

The main point is that water, even water satisfactory for kitchen use and bathing, varies greatly in pH and mineral content depending on its source. Good evidence of this is that water softeners are considered essential household equipment in some communities and not necessary in others.

Actually, I have theorized for some years that an unrecognized difference between those people whose experiments in growing bonsai are rewarding right from the beginning and those who struggle for awhile before giving up in frustration because “they don’t have the touch,” may be the quality of their water. A related observation is that, while cautions against wetting the foliage of one’s trees during the heat of midday to avoid burn are common in bonsai literature, many growers do this routinely with no damage. Again, it seems likely that this seeming contradiction is explained easily by differences in water quality.

So, what does one do if poor water quality is suspected? It would be hard to go wrong to begin by obtaining an analysis of your water. Those using water from a municipal supply will find this as easy as requesting a copy of their water analysis from the local Water Department. (The Federal Safe Drinking Water Act Amendments of 1996 require “providers” to make water analysis information available to their “customers.”) People who rely on their own wells or other private water sources, can learn where a horticultural water analysis can be obtained by contacting their local Agricultural Extension Service office. (Water Standards for Horticultural Use, offered by Dr. John C. Peterson at the American Bonsai Society’s 1990 Annual Symposium, can be found at the end of this article.)

Another way of evaluating the quality of your water for horticultural use is to obtain a package of radish seeds. Radish seedlings are known to be sensitive to high salt concentrations and other water contaminants. Plant these seeds in a relatively sterile growing medium in a number of containers. Then water some pots with your household water and others with distilled water or other mineral-free water. Noticeable differences in seed germination and seedling growth between treatments -- better germination and stronger growth in the mineral-free water – will be strong evidence that your household water is a significant problem.

Once you learn that your water is not good for growing plants, what are your options short of acid injection like the commercial growers do? Of course the amount of water needed for routine watering will be a major factor in deciding what might work for you. For a small number of plants the answer may be as simple as purchasing distilled water. If available in large enough quantity, water discharged from air conditioning equipment or water collected by a dehumidifier will also work very well.

And, even though not pure (we have all heard of acid rain), rain water will typically be far better for growing plants than mineral loaded water. With a gutter, and a downspout rigged to direct water into a container of some kind, it will be surprising how much water can be collected.

One simple water treatment remedy being used by a number of bonsai enthusiasts in parts of the country with very hard water is routinely to add white vinegar, a tablespoon or two per gallon, to the water used on their bonsai. Others have written of adding as much as a cup of vinegar per gallon of water and applying this as a monthly drench. Actually, a little experimenting with vinegar additions to your water may be all you need to do to learn more about its quality.

Another simple, though slow acting, remedy used some in commercial production is to treat plants with powdered sulfur either by scattering it over the soil surface or mixing it into the soil. One advantage in doing this is that it makes it fairly simple to treat consistently weak and off-color plants while ignoring those that seem to be fine without the extra attention. This dosage doesn’t have to be too precise, but a teaspoon of powdered sulfur per gallon of soil is a reasonable target rate for experimentation.

A more expensive but almost foolproof remedy recommended as cost effective by horticultural scientists is use of a reverse osmosis (RO) water treatment system. This equipment is now widely available. Actual costs vary depending on the volume of water required. (I know personally two very active bonsai growers who went through considerable frustration with ongoing foliage disfiguration and unexplained tree loss before they decided their problems had to be water related and had RO systems installed at their homes.)

To summarize, water varies greatly depending on its source. Unresolved problems with your bonsai may be the result of poor quality water for growing plants. Although having low quality water is unfortunate, there are remedies available. Clearly, there is little to be lost by investigating your options and the potential for improvement in your trees can be great.

Desirable Ranges for Problem Water Parameters

Distributed by Dr. John C. Peterson, June 29, 1990 at American Bonsai Society Symposium at Ohio State University:

pH: 5.0 to 6.5
Soluble Salts (Conductivity): 0 to l.5 mmhos per cm (1 mmho is equal to 1000 umhos)
Calcium: 0 to 120 ppm (1 ppm is equal to 1 mg per liter)
Magnesium: 0 to 24 ppm
Sodium: 0 to 50 ppm
Chloride: 0 to 140 ppm
Boron: 0 to 0.8 ppm
Fluoride: 0 to 1 ppm
Sulfate: 0 to 240 ppm
Alkalinity: 0 to 100 mg per liter CaCO3

February 2009 update of March 2005 AABS Newsletter column

GrimLore · May 16, 2017

Gustavo Martins said:
Does this make any sense to you? I'd like to hear from you on this...

All you wrote makes sense but I think of a plants needs differently. I find either inorganic or organic mixes of soil first off work just fine IF they drain very good. Now with that stated some plants in Bonsai require a more acidic substrate, for example Azalea for optimal growth.
I firmly do not believe after years of growing at our last house that being on a sophisticated system as RO and since 1013 here where we have a good filter on the whole house for substrate and chlorine it makes no difference, and where I lived in New York unfiltered worked just as good. Walter Pall states firmly that plants don't care and if you can drink it so can they - I read that after discovering it on my own...
Good draining substrate if FAR more important then water quality and pretty simple to understand why as no matter what you put in the substrate it flushes quickly and is flushed further by rain. The primary reason I fertilize at rather large doses - it passes through and does not hang around, build up, or cause problems.
Back to Azalea and acidic loving plants - Kanuma(a pumice like material) for a great draining substrate does the job. If you are looking at or liking Organics a heavy amount of peat moss has a much similar acidic content. No matter what water you use...
Soil/Substrate can also be amended with Sulfur, I often use it diluted to buff acidic levels and provide a natural fungicide in the soil/substrate. I also use it on occasion in landscape plants as I see fit - I am however talking about potted plants.
Just my 2 cents on what happens in 2 different States, 3 different locations, and 3 different water qualities.

Grimmy

wireme · May 16, 2017

Gustavo Martins said:
Hey,

I've been reading some people complaining about their water pH and how a high or low pH can affect plant growth.

Given my background in biological sciences, I have a slightly diverging view about the relative importance of pH in the water we use to water our plants. Let's see if I can make myself understood.

Osmotic shock:
Plants uptake water via their roots via a process called osmosis. The function of this process is dependent upon the amount of Total Dissolved Solids (TDS) in the water.

The catch, as it relates to this discussion, is that any action that changes the pH of the water is generally a result of the change in TDS. Hard water generally has high TDS levels, high pH, high KH, and high GH. Soft water generally is low in TDS, a low pH, KH, and GH. The occurrence of a pH rise (or decline) is generally accompanied by an increase (or decrease) in TDS. It is this change in TDS and the resulting change in osmotic pressure that impacts our plants. The problem is not a shift in pH to the pH in itself; it's the TDS: hard water vs soft water.

Note: I'm not talking about extreme pH (or pOH) levels, of course. These would burn the plants immediately. Hell, they would burn our hands too.

pH effects on other substances:
pH has an effect on the toxicity of ammonia. At a lower pH, ammonia is converted into ammonium, which is not toxic. As the pH increases, ammonium is converted into ammonia, which is toxic (at least to animals, not sure for plants). What is less known is that pH has the same effect on other toxic substances such as chromium, mercury, copper, and iron.

As the pH falls (solution becomes more acidic) many insoluble substances become more soluble and thus available for absorption. For example, 4 mg/L of iron would not present a toxic effect at a pH of 4.8. However, as little as 0.9 mg/L of iron at a pH of 5.5 can cause fish to die. (again, I'm not sure how important this is for plants).

So, It is not the the pH itself that causes issues. It is the physiological effects associated with TDS and/or the synergistic effects of pH increases, or decreases, on toxic compounds within the water.

How does this affect us?
Plants have evolved to use rain as main source of watering. Rainwater is often low in TDS (all salts are removed during evaporation). It is thus a soft water (regardless of its pH). Compared to this, roots are hypertonic and so water can enter the roots via osmosis without any problems. People leaving in areas with soft water should have, generally, no problems regarding this issue (note that the substrate can change this but since most people are using free-draining inorganics soils, this should be no problem). However, there are people that live in areas with hard water. Using vinegar (or other acid) is going to change pH (to some extent) but not TDS. So I am pretty sure this is not going to have any direct effect on plant growth (although it can indirectly if it does affect the toxicity of some substances - I am yet to study this regarding plants).

The only solution for those of use living in hard water areas is to use soft water (collected rainwater) or remove salts from tap water (via reverse osmosis). Any other solution that does not address the excess of salts (TDS) is only affecting pH and has little influence on osmosis, hence how plants absorb water.

Related to this:
This is also the reason why too much fertilization can "burn" the roots. As the concentration of ferts build up in the soil, so does TDS. When we water, this water absorbs the salts in the soil and becomes hard water. Above a certain threshold, the water around the roots may become hypertonic relative to the roots so that osmosis occurs the other way around: from the roots to the soil. Plants cannot absorb water and "burn". This effect should be minimal with the use of well-draining inorganic soils as excess of ferts are removed by watering and thus preventing the build up of TDS.

Does this make any sense to you? I'd like to hear from you on this...

I really don't know anything about this stuff but I think plants also uptake a lot of water through passive absorption where no osmotic pressures are required. Basically suction due to transpiration. Does that change anything?

Gustavo Martins · May 16, 2017

Stickroot said:
I have very basic well water and it tests around 9! So yes I do go through about a gallon of General Hydro acid a year bringing it down.
I have noticed the biggest difference in cutting, more acidic water roots them faster.

Let's analyse what your evidence.

1. My discussion above is about water absorption by the roots and pH. So the above does not apply to a rootless cutting. Rooting is a different thing. I do not know the science of it but it is possible that pH may affect it due to the electrical charges... But again, I am speculating here.

2. "roots faster". Any data? Without any data it is hard to judge what fast means to you...

3. I do not know what General Hydro acid is. Do you need to wear gloves and handle it outside? If not, that's probably a weak acid (just like vinegar). The fact that you can change the pH of the water you have by using (and assuming you have) a weak acid, means that you have a reasonably soft water. If you had hard water you would not be able to change its pH with a little bit of acid. Hard water has a lot of buffer capacity against pH oscillations.

4. I'm finding a pH of 9 really high. Seawater, which is hard as hell, only has 8.3-8.4. How are you measuring it? Are you using those pH strips that give you a colour? If so, let me tell that those are not accurate or precise. They value will change with the relative humidity of the air... They are, essentially, crap.

Does the above make sense?

Gustavo Martins · May 16, 2017

Waltron said:
Could It Be Your Water?

by Jack Wikle

There is no need to read farther --- unless you are curious --- if you are one of those people whose bonsai consistently look healthy and grow well. On the other hand, reading more could be helpful if your trees fail to thrive in spite of your conscious effort to follow some old but good advice: water thoroughly and leach frequently to keep unwanted salts from accumulating in your bonsai soil. This is especially true if you keep seeing the common symptoms of what horticultural scientists know as low quality water: persistently weak green or yellow-green leaves with darker green veins often accompanied by scorched-looking leaf tips and burned leaf margins (most prominent toward the leaf’s tip).

By definition, “pure water” is nothing but water. But, being the “universal solvent,” water available to us from lakes, waterways, wells, the local Water Department or even a rain barrel is never pure. Actually, the “load” of dissolved minerals and other substances found in water – even water acceptable for use in human consumption and plant irrigation -- is highly variable.

People dealing regularly with water quality commonly make a distinction between “surface water” and “ground water.” Surface water is the runoff of rain into ponds, lakes and rivers. Ground water,” is water which typically has seeped deep into the ground through many tons of soil and rock before emerging as spring water or before being pumped back to the earth’s surface from a well. The reason for this classification is that surface water is relatively “soft,” that is, low in dissolved mineral content. Ground water, on the other hand, having accumulated lots of dissolved minerals as it settled deep into the earth is “hard,” i.e., high in mineral content. Where available, surface water is almost always superior to ground water for plant irrigation purposes.

However, we need to be aware that knowing your city’s water source is a river or reservoir does not necessarily mean it will be as low in pH and mineral content as one might expect. We are told it is not uncommon for municipalities to add chemicals, typically calcium hydroxide, to surface water in order to raise its pH (make it less acid) as a way of minimizing corrosion of public and private plumbing. These additives make water less satisfactory for plant use.

Technical publications directed to commercial growers of irrigated greenhouse and nursery crops make it very clear that water quality is a major factor in their success or failure. The standard recommendation is that a comprehensive horticultural water analysis should be done before settling on a growing site. Tables specifying recommended ranges for alkalinity, pH (not the same as alkalinity), soluble salts (usually measured by electrical conductivity), and six or seven specific elements can also be found in this literature. It is relatively common today for commercial growers stuck with low quality water to inject acid into it to make it better for plant use; even though this adds significantly to their production costs.

The main point is that water, even water satisfactory for kitchen use and bathing, varies greatly in pH and mineral content depending on its source. Good evidence of this is that water softeners are considered essential household equipment in some communities and not necessary in others.

Actually, I have theorized for some years that an unrecognized difference between those people whose experiments in growing bonsai are rewarding right from the beginning and those who struggle for awhile before giving up in frustration because “they don’t have the touch,” may be the quality of their water. A related observation is that, while cautions against wetting the foliage of one’s trees during the heat of midday to avoid burn are common in bonsai literature, many growers do this routinely with no damage. Again, it seems likely that this seeming contradiction is explained easily by differences in water quality.

So, what does one do if poor water quality is suspected? It would be hard to go wrong to begin by obtaining an analysis of your water. Those using water from a municipal supply will find this as easy as requesting a copy of their water analysis from the local Water Department. (The Federal Safe Drinking Water Act Amendments of 1996 require “providers” to make water analysis information available to their “customers.”) People who rely on their own wells or other private water sources, can learn where a horticultural water analysis can be obtained by contacting their local Agricultural Extension Service office. (Water Standards for Horticultural Use, offered by Dr. John C. Peterson at the American Bonsai Society’s 1990 Annual Symposium, can be found at the end of this article.)

Another way of evaluating the quality of your water for horticultural use is to obtain a package of radish seeds. Radish seedlings are known to be sensitive to high salt concentrations and other water contaminants. Plant these seeds in a relatively sterile growing medium in a number of containers. Then water some pots with your household water and others with distilled water or other mineral-free water. Noticeable differences in seed germination and seedling growth between treatments -- better germination and stronger growth in the mineral-free water – will be strong evidence that your household water is a significant problem.

Once you learn that your water is not good for growing plants, what are your options short of acid injection like the commercial growers do? Of course the amount of water needed for routine watering will be a major factor in deciding what might work for you. For a small number of plants the answer may be as simple as purchasing distilled water. If available in large enough quantity, water discharged from air conditioning equipment or water collected by a dehumidifier will also work very well.

And, even though not pure (we have all heard of acid rain), rain water will typically be far better for growing plants than mineral loaded water. With a gutter, and a downspout rigged to direct water into a container of some kind, it will be surprising how much water can be collected.

One simple water treatment remedy being used by a number of bonsai enthusiasts in parts of the country with very hard water is routinely to add white vinegar, a tablespoon or two per gallon, to the water used on their bonsai. Others have written of adding as much as a cup of vinegar per gallon of water and applying this as a monthly drench. Actually, a little experimenting with vinegar additions to your water may be all you need to do to learn more about its quality.

Another simple, though slow acting, remedy used some in commercial production is to treat plants with powdered sulfur either by scattering it over the soil surface or mixing it into the soil. One advantage in doing this is that it makes it fairly simple to treat consistently weak and off-color plants while ignoring those that seem to be fine without the extra attention. This dosage doesn’t have to be too precise, but a teaspoon of powdered sulfur per gallon of soil is a reasonable target rate for experimentation.

A more expensive but almost foolproof remedy recommended as cost effective by horticultural scientists is use of a reverse osmosis (RO) water treatment system. This equipment is now widely available. Actual costs vary depending on the volume of water required. (I know personally two very active bonsai growers who went through considerable frustration with ongoing foliage disfiguration and unexplained tree loss before they decided their problems had to be water related and had RO systems installed at their homes.)

To summarize, water varies greatly depending on its source. Unresolved problems with your bonsai may be the result of poor quality water for growing plants. Although having low quality water is unfortunate, there are remedies available. Clearly, there is little to be lost by investigating your options and the potential for improvement in your trees can be great.

Desirable Ranges for Problem Water Parameters

Distributed by Dr. John C. Peterson, June 29, 1990 at American Bonsai Society Symposium at Ohio State University:

pH: 5.0 to 6.5

Soluble Salts (Conductivity): 0 to l.5 mmhos per cm (1 mmho is equal to 1000 umhos)

Calcium: 0 to 120 ppm (1 ppm is equal to 1 mg per liter)

Magnesium: 0 to 24 ppm

Sodium: 0 to 50 ppm

Chloride: 0 to 140 ppm

Boron: 0 to 0.8 ppm

Fluoride: 0 to 1 ppm

Sulfate: 0 to 240 ppm

Alkalinity: 0 to 100 mg per liter CaCO3

February 2009 update of March 2005 AABS Newsletter column

That's more or less in agreement with what I said... no?

0soyoung · May 16, 2017

AFIK the issue with pH concerns the uptake of minerals, particularly iron. Chlorosis is the classic symptom of the soil pH being too high (basic). Roots exude protons (H+ ions) to obtain minerals that are bound to soil particles. The protons substitute for the positive mineral ion complex, releasing them from the soil. If the soil is too alkaline, the minerals are very tightly bound and, hence, cannot get loaded into the roots.

Gustavo Martins · May 16, 2017

GrimLore said:
All you wrote makes sense but I think of a plants needs differently. I find either inorganic or organic mixes of soil first off work just fine IF they drain very good. Now with that stated some plants in Bonsai require a more acidic substrate, for example Azalea for optimal growth.
I firmly do not believe after years of growing at our last house that being on a sophisticated system as RO and since 1013 here where we have a good filter on the whole house for substrate and chlorine it makes no difference, and where I lived in New York unfiltered worked just as good. Walter Pall states firmly that plants don't care and if you can drink it so can they - I read that after discovering it on my own...
Good draining substrate if FAR more important then water quality and pretty simple to understand why as no matter what you put in the substrate it flushes quickly and is flushed further by rain. The primary reason I fertilize at rather large doses - it passes through and does not hang around, build up, or cause problems.
Back to Azalea and acidic loving plants - Kanuma(a pumice like material) for a great draining substrate does the job. If you are looking at or liking Organics a heavy amount of peat moss has a much similar acidic content. No matter what water you use...
Soil/Substrate can also be amended with Sulfur, I often use it diluted to buff acidic levels and provide a natural fungicide in the soil/substrate. I also use it on occasion in landscape plants as I see fit - I am however talking about potted plants.
Just my 2 cents on what happens in 2 different States, 3 different locations, and 3 different water qualities.

Grimmy

Yes. I also said this. If one uses free-draining and inorganic soils there should be no problem... unless your tap water is really hard by default.

I do not really understand the concept of having an acidic soil. I mean, acidity is a quality of liquids, not solids... Sure, some soils can leash/absorb salts into the water and hence affect its pH. Is this what you mean? But then again, these soils mostly likely affect pH via changes in TDS. So my question is: do Azaleas or other acid-lover plants really enjoy acidic conditions or is it a low salinity (TDS) condition, which in turn, implies a low pH? Just because there is a correlation does not necessarily means there is a causation...

Gustavo Martins · May 16, 2017

0soyoung said:
AFIK the issue with pH concerns the uptake of minerals, particularly iron. Chlorosis is the classic symptom of the soil pH being too high (basic). Roots exude protons (H+ ions) to obtain minerals that are bound to soil particles. The protons substitute for the positive mineral ion complex, releasing them from the soil. If the soil is too alkaline, the minerals are very tightly bound and, hence, cannot get loaded into the roots.

ok I think that makes sense. I did not know about this, although this is kind in the same line of though about the toxicity and how it varies with pH.
I also know that iron has numerous forms of ion which are affected by pH. So pH should affect the form of the Fe+ ion, which may affect the ability of the plant to uptake it.

Gustavo Martins · May 16, 2017

wireme said:
I really don't know anything about this stuff but I think plants also uptake a lot of water through passive absorption where no osmotic pressures are required. Basically suction due to transpiration. Does that change anything?

Well osmosis is a passive mechanism. I think you are partially right. Yes, transpiration pushes water up however, there is difference. There really there is no barrier against water movement inside the plant. In contrast, there is barrier (a membrane) between the roots and the environment. So here is osmosis. Inside the plants is just water (and salts) movement.

Stickroot · May 16, 2017

This palm sized Itoigawa has managed to stay alive for years on adjusted water.
Yawn...

I have to admit the only reason I adjust and ever knew to is because a horticulture and woodies professor who also collects Bonsai told me I should be doing it.
So many variables in growing things.

So much to read.

So much to think about.

So many neat things in the world.

I like trees.

Lots of trees.

@sorce what are you doing?

Wanna go ride bikes?

sorce · May 16, 2017

Stickroot said:
@sorce what are you doing?

Wanna go ride bikes?

You said you stop at ONE 13%er!

Lol! Nude!

PH reminds me of

Natural Selection will only allow me to keep trees in the range of PH they are in.

Sorce

Vance Wood · May 16, 2017

Stickroot said:
This palm sized Itoigawa has managed to stay alive for years on adjusted water.
Yawn...
View attachment 145951
I have to admit the only reason I adjust and ever knew to is because a horticulture and woodies professor who also collects Bonsai told me I should be doing it.
So many variables in growing things.

So much to read.

So much to think about.

So many neat things in the world.

I like trees.

Lots of trees.

@sorce what are you doing?

Wanna go ride bikes?

You need to consider giving this little guy a bit more light. More light will encourage the foliage to become more compact. You should also consider removing all of the needles that grow on the underside of all of the branches. This will thin out excess material and allow light to enter the interior of the tree and promote growth.

Stickroot · May 16, 2017

sorce said:
You said you stop at ONE 13%er!

Lol! Nude!

PH reminds me of

Natural Selection will only allow me to keep trees in the range of PH they are in.

Sorce

No sippy for me. I welded over head on a lift forty feet up at a club fitness in central Illinois today for 11 hours, I'm sleepy and can't think about much.

Blood sugar is funny I think.

Stickroot · May 16, 2017

Vance Wood said:
You need to consider giving this little guy a bit more light. More light will encourage the foliage to become more compact. You should also consider removing all of the needles that grow on the underside of all of the branches. This will thin out excess material and allow light to enter the interior of the tree and promote growth.

I just cut down 70, yes 70! Massive white oaks that we're all around my house so that I could focus on my pines and junipers. And my damn grass!

I hate leaves! Oak leafs!

Leafs suck!

No more leafs for me!

Lots of light!

I have a White pine that HATES ME! Because I have deprived it of light for way to long.
Having no light has made me totally boo.

It's not really this green in the day light

sorce · May 16, 2017

Stickroot said:
club fitness

! Stationary Bikes!

Did a Planet Fitness once.

We did a bunch of Ass backwards shit today...

(I assume PH talk is adjourned, it is....
PH

only 1-7!)))

It was nice to get away from the galvanized.

My guy at work name is Cam. Like my son.
I joke he can put a stick in each hand and...

Dual Overhead Cam!

Sorce

Stickroot · May 16, 2017

I was WAITING!

I someone post a chart.

People that grow dope are REALLY picky about PH.

What does PH stand for?

I have put two sticks in the same holder and run two beads side by side for multi pass.

I try to weed out the galvinize by taxing them to broke!

But new metal!

Why have galvinize with rusty weld?!?

Oh, I save a dollar, that's why.

Thanks for the talk, therapeutic

63pmp · May 16, 2017

Gustavo Martins said:
any action that changes the pH of the water 0is generally a result of the change in TDS.

No, the concentration of H+ is 1000 to 10000 x less then what TDS is. Any effect of pH to TDS is negligible.

Hard water generally has high TDS levels,

No, hard water is the ratio of calcium + magnesium ions to sodium. nothing to do with TDS other then they are dissolved salts. You can have low TDS and still have hard water.

high KH, and high GH.

I've never heard of KH or GH, what are these?

Soft water generally is low in TDS, a low pH, KH, and GH.

No, for same reason as stated above, TDS has no bearing on pH

The occurrence of a pH rise (or decline) is generally accompanied by an increase (or decrease) in TDS. It is this change in TDS and the resulting change in osmotic pressure that impacts our plants. The problem is not a shift in pH to the pH in itself; it's the TDS: hard water vs soft water.

NO, this is completely wrong. pH only relates to the concentration of hydronium ions; salts can come and go and pH remains the same. You are probably thinking of soil pH tests done with CaCl2 solution and the consequent drop of pH. This occurs because H+ is pushed off exchange sites on soils by Ca2+, not from a change in solution ionic strength.

pH effects on other substances:
pH has an effect on the toxicity of ammonia. At a lower pH, ammonia is converted into ammonium, which is not toxic. As the pH increases, ammonium is converted into ammonia,

Sort of, ammonia is not converted back to ammonia until the solution reaches a pH of 7.3 (from memory) Ammonia is toxic to plants, but at higher concentrations than for animals.

chromium, mercury are not found in potting mixes, and many soils for that matter,

copper, and iron are soluble at all pH ranges. The insoluble metals that are pH sensitive are those that form stable hydrates, such as aluminium.

As the pH falls (solution becomes more acidic) many insoluble substances become more soluble and thus available for absorption.

For example, 4 mg/L of iron would not present a toxic effect at a pH of 4.8. However, as little as 0.9 mg/L of iron at a pH of 5.5 can cause fish to die. (again, I'm not sure how important this is for plants).

So you are saying that iron is less toxic at lower pH?

So, It is not the the pH itself that causes issues.

Yes it is. pH affects plants nutrient uptake at the cell wall, especially iron as it require two H+ ions to co-transport for each Fe2+ ion. At higher pH there is insufficient H+ to be available for co-transport so iron uptake stops.

It is the physiological effects associated with TDS and/or the synergistic effects of pH increases, or decreases, on toxic compounds within the water.
TDS does inhibit plant growth simply by its affect on osmosis, not on pH, that and nutrient toxicities.

Irrigation water alkalinity is the main driver of pH change in potting media, pH of irrigation water has much less impact as imagined. The other driver is fertilizer N form, nitrate will raise pH while ammonium will lower it.

These are my thoughts.

Paul

hemmy · May 16, 2017

Gustavo,

Good topic!

Dr. Whitcomb has a good article on pH:
https://rootmaker.com/sites/default/files/pdf/pHFactorContainersE.pdf

He states that pH is the symptom of high levels of typically calcium, magnesium, or sodium.

As this UF presentation states, highly alkaline water has carbonates and bicarbonates which form salt complexes with Ca, Mg, etc. making these nutrients and other micronutrients unavailable for uptake. Acidifying the water converts some of the bicarbonates.

Highly porous substrates and flushing while watering should mitigate some of this problem.

But azaleas and other 'acid-loving' plants, apparently are less efficient at uptaking minerals making them sensitive to alkaline water which is forming salts that tie up minerals.

pH: is it relevant?

Omono

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