gases from the air have a role in pH

[mad librettist]

pH is a measure of the acidity or basicity of a solution. It approximates but is not equal to p[H], the negative logarithm (base 10) of the molar concentration of dissolved hydrogen ions (H+).

-wiki

sorry the title is not accurate.

I have seen many, including myself, confused by this fact: pH can change drastically in soil without the gardener adding any acids or bases as liquids or powders.

Yet when gardeners speak of pH, the discussion seems to be limited to solids and liquids stirred in or poured on. Microbial action, plain old diffusion, and water saturation all play a role. Hydrogen coming from the air, or going into the air, or going from solution to being locked into a compound, will change the pH. In my acid fermentation, for instance, nobody adds any acid. I start with kitchen scraps that are as an aggregate pretty neutral, and wind up with something as acidic as orange juice. But I didn't add any pH down to get from close to 7 to below 3.5. What would happen if I treated my scraps with lime before fermenting, or started with more alkaline material?

This may explain part of the age-old conflict of pH or don't pH. Through microbial action it is possible to raise or lower acidity, it's just most "microbial gardeners" don't have to think about it too much. The dominant organisms they favor, which share environmental preferences with their plants, can do the job for them in many cases.

Likewise, it seems many gardeners may have water or soil alkalinity beyond what is common. These outliers also have a point. Microbes can do a lot, but that doesn't mean they will do what you want in all cases. Sometimes you need to change the case.

thoughts? rebuttals? evidence for and against?

 

[SuperHemp]

peat is acidic, and as it breaks down the soil becomes more acidic.. common problem in soils containing peat.

 

[mad librettist]

et when gardeners speak of pH, the discussion seems to be limited to solids and liquids stirred in or poured on.

I was trying to broaden the conversation, but thanks.

Broccoli is basic or neutral, I think, and after fermentation is around 3.5. None of the ingredients thrown into the fermentation are very acidic...

Does that not show that the base pH of a substrate does not necessarily predict the pH of that substrate after microbial action is taken into account?

 

[VerdantGreen]

the gas in air that has one of the biggest influences is CO2, carbon dioxide - this is why rainwater is usually acidic.

as i have often pointed out, i reduce the pH of my 9ish tap water down to around 6 before watering. the reason why i often post this is because i dont want people to think they have somehow 'failed' at organics by amending their pH - really it is making the water a more 'natural' pH for the plant imo.

what works for 9 out of 10 people will not necessarily work of the other 1

V.

 

[mad librettist]

that's one of the views I was hoping to hear verdant. I thought of you when I made this thread, since you are a perfect example of a super competent organic gardener who directly manipulates pH. I'm wondering if i would have to do the same to have success in your neck of the woods, or if there are options. I also support your notion that one should not feel in violation of the sacred laws of organics for having a pH pen, or that not checking pH is a sign of anything except being lucky enough not to have to.

I'd also like to know if there are local variation in microfauna/flora that are built to deal with alkalinity, so we can expand the circle of those lucky enough not to need to think about soil pH.

Verdant, you are referring to carbonic acid, yes? It's actually lowering the pH of the ocean faster than convection can bring buffers up from the deep. This eats away at shells, particularly those of tiny shelled plankton.

So, while carbonic acid takes distilled water down to below 6, is every acid that takes you below 6 equally hard to buffer? I just don't know the science here.

 

[VerdantGreen]

yes carbonic acid - and rain is naturally around 5.8 - although pollution etc can take it lower to make 'acid rain'

the way i see it, if i use Dolomite in the soil and then water at around 6, i can be confident that my soil pH is between 6 and 7 which is exactly where i want it. i have never measured pH of runoff or anything like that.

V.

 

[Trichgnomes]

the gas in air that has one of the biggest influences is CO2, carbon dioxide - this is why rainwater is usually acidic.

as i have often pointed out, i reduce the pH of my 9ish tap water down to around 6 before watering. the reason why i often post this is because i dont want people to think they have somehow 'failed' at organics by amending their pH - really it is making the water a more 'natural' pH for the plant imo.

what works for 9 out of 10 people will not necessarily work of the other 1

V.

The water that comes out of my tap, unless my pH pen is off (which is possible although I did calibrate immediately prior to testing) is 7.1. Slightly alkaline, but I have never 'adjusted' it before watering. I am curious though, as to if it would be better, worse or negligible if I were to do so, seeing as how my initial pH is significantly lower than yours.

My water is artesian however, and my household (mammals, plants, microbes and the like) all love it.

 

[VerdantGreen]

The water that comes out of my tap, unless my pH pen is off (which is possible although I did calibrate immediately prior to testing) is 7.1. Slightly alkaline, but I have never 'adjusted' it before watering. I am curious though, as to if it would be better, worse or negligible if I were to do so, seeing as how my initial pH is significantly lower than yours.

My water is artesian however, and my household (mammals, plants, microbes and the like) all love it.

well, 7.1 is pretty ideal - im sure the humic acid etc and citric acid etc exuded by the roots will be easily amend that.

mad pointed out something that most people dont consider about pH - it is a LOGARYTHMIC scale - so pH 8 is 10 times more acidic than pH 7. pH 9 is 100 times more acidic than pH 7 (neutral).

this chart shows that most elements are optimally absorbed by plants at pH between 6 and 7. interestingly iron is one that is better absorbed at more acidic pH - and thats exactly what 'acid loving' plants are - they are simply plants that need more iron and thus grow better in lower pH

V.

 

[DARC MIND]

i usually use rain water but come summer ill back to tap, my tap is 7.1-7.3ish
and have been thinking of adjusting before drenching like verdant does. but i was thinking of using real apple cider vinegar instead or maybe a little lacto bacilli
what do you guys think??

 

[Carl Carlson]

the gas in air that has one of the biggest influences is CO2, carbon dioxide - this is why rainwater is usually acidic.

as i have often pointed out, i reduce the pH of my 9ish tap water down to around 6 before watering. the reason why i often post this is because i dont want people to think they have somehow 'failed' at organics by amending their pH - really it is making the water a more 'natural' pH for the plant imo.

what works for 9 out of 10 people will not necessarily work of the other 1

V.

while they're related, it's not the pH of the water, but the alkalinity level (buffering capacity) of the water that can change the pH of the soil.

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

 

[blazesck]

the gas in air that has one of the biggest influences is CO2, carbon dioxide - this is why rainwater is usually acidic.

as i have often pointed out, i reduce the pH of my 9ish tap water down to around 6 before watering. the reason why i often post this is because i dont want people to think they have somehow 'failed' at organics by amending their pH - really it is making the water a more 'natural' pH for the plant imo.

what works for 9 out of 10 people will not necessarily work of the other 1

V.

What do you use to get the pH of your water down? Our pH testing kit only went up to 9, and water straight out of the tap shows 9, so I can only assume it's actually higher. It definitely made growing difficult before we got everything dialed in. We used to use vinegar to get the pH down and now use reconstituted lemon juice because it is readily available.

 

[VerdantGreen]

Blazesck and DARC, i use citric acid - i buy powder off ebay and then make a bottle of pH down by dissolving a teaspoon or two in half a litre of water - it then takes a tablespoon or so of this solution to bring my pH down to 6 ish

having done some research in citric acid it seems that this is one of the acids that plant roots naturally exude to facilitate their feeding process - it helps chelate minerals too i think - others may know more about this but i am happy it is a good method. not sure about vinegar or what acetic acid does to help/hinder plants

i usually use rain water but come summer ill back to tap, my tap is 7.1-7.3ish
and have been thinking of adjusting before drenching like verdant does. but i was thinking of using real apple cider vinegar instead or maybe a little lacto bacilli
what do you guys think??

 

[VerdantGreen]

while they're related, it's not the pH of the water, but the alkalinity level (buffering capacity) of the water that can change the pH of the soil.

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

hi Carl, im not sure i quite get you here. i am familiar with alkali clay from the link - thats what i grow my veggies in
i also understand that adjusting the pH of my water does not necessarily change it permanently depending on the mineralisation of the water.
here is what i do when i water - it works great for me - but perhaps you can tell me if i am getting something wrong.

i use dolomite lime in my potting soil mix as a buffer, but i lower the pH of my watering water to around 6, sometimes a bit lower, so when i water the pH of the soil (or water+nutes in the soil) is tempoarily lowered for a few hours - which allows the pH to sweep slowly back to 7 and various nutrients pass through their optimal pH for being used by the plant.

i did a simple experiment with my water - i stirred some dolomite lime into a glass of water and then reduced the pH to 5. it took around 8 hours for the dolomite to buffer the pH back to 7 - so i am reasonably confident that it does what i want it to do.

V.

 

[mad librettist]

FYI citric acid is also the cure for chloramine...

 

[Carl Carlson]

hi Carl, im not sure i quite get you here. i am familiar with alkali clay from the link - thats what i grow my veggies in
i also understand that adjusting the pH of my water does not necessarily change it permanently depending on the mineralisation of the water.
here is what i do when i water - it works great for me - but perhaps you can tell me if i am getting something wrong.

i use dolomite lime in my potting soil mix as a buffer, but i lower the pH of my watering water to around 6, sometimes a bit lower, so when i water the pH of the soil (or water+nutes in the soil) is tempoarily lowered for a few hours - which allows the pH to sweep slowly back to 7 and various nutrients pass through their optimal pH for being used by the plant.

i did a simple experiment with my water - i stirred some dolomite lime into a glass of water and then reduced the pH to 5. it took around 8 hours for the dolomite to buffer the pH back to 7 - so i am reasonably confident that it does what i want it to do.

V.

I don't think you're doing anything wrong, but from my limited understanding of chemistry, it doesn't sound as if you're actually accomplishing that which you think you are (temporarily changing the pH of the soil solution).

I think the experiment with the water tells us a little bit about the acid buffering capacity of the water at your location, but perhaps not much else.

When you add acid to the water, and lower the pH, hydrogen ions are produced. When you water a dry soil, the pH of the soil solution temporarily rises. Than the hydrogen and nutrient ions that were present in the water, bind with the soil colloids and the pH stabilizes.

I could be all wrong on this and if so, definitely want to be corrected. Looking forward to your response.

 

[secondtry]

FYI citric acid is also the cure for chloramine...

Hey Mad.

I use ascorbic acid for that because I have not been able to find much info on citric acid removal of chloramines, do you have links I could check out? Thanks.


@ V,

I too have used citric acid if the drench water pH is above 7, I lower it to 6.8 if so. I wold like to read know the effects of citric acid upon soil food web microbes, hmmm.

 

[mad librettist]

I have no links because I meant to say ascorbic acid

I was thinking vitamin C and jumped to citrus and citric I guess. who knows.

you think dried and ground rose hips would work? A lot of us walk by a shitload every year and don't know it.

 

[Carl Carlson]

V-

When you have a chance, read page 205 of this book via google preview:

http://books.google.com/books?id=KO...er&source=gbs_navlinks_s#v=onepage&q=&f=false

 

[SupraSPL]

One thing I have noticed in regard to R/O water and distilled water (and so I assume most rain water) is that despite its PH of ~6.0-6.5, it seems to have relatively low buffering capacity. If I add a touch of 8.5ph spring water or a bit or liquid organic ferts, the PH goes up (especially blooming ferts). Then when I run it through a peat based soil mix that has been limed, it runs off at about 6.8-7.0 which seems to be working well.

I'm using liquid organic ferts because I don't fully understand solid ferts, but it is on my list of things to research.

 

[VerdantGreen]

I don't think you're doing anything wrong, but from my limited understanding of chemistry, it doesn't sound as if you're actually accomplishing that which you think you are (temporarily changing the pH of the soil solution).

I think the experiment with the water tells us a little bit about the acid buffering capacity of the water at your location, but perhaps not much else.

When you add acid to the water, and lower the pH, hydrogen ions are produced. When you water a dry soil, the pH of the soil solution temporarily rises. Than the hydrogen and nutrient ions that were present in the water, bind with the soil colloids and the pH stabilizes.

I could be all wrong on this and if so, definitely want to be corrected. Looking forward to your response.

hi carl, thanks for the link in your other post - that makes sense but i still feel that i am pushing my pH in the right direction making my water 6 instead of it being nearly 9 before watering. i have also observed leaf problems associated with pH when i have not done this. i understand that good organic soil has buffering capabilities but my worry is that if i add dolomite to my soil and water with water pH9 then my soil pH is unlikely to go below 7 which would not be desirable for growing weed - which actually prefers pH around 6.5.

in regard to your comment about my experiment, i was pretty sure that it was mainly the dolomite lime dust that i mixed with the water that nuetralised the acid in 8 hours - and to check this i today measured the pH of some tapwater (with no lime) that i reduced to pH 6.5 2 days ago - its pH was 7.5 so this tells me that using citric acid keeps my water at the desired pH for long enough to do what i think it is doing. this plus the fact i get fantastic results doing what i already do makes me reticent to change anything too much

V.