sphagnum acidification

[ChrisFL]

Just a neat little home anecdotal experiment. I have an instrument grade pH probe (don't ask). Our tap water here in Austin has a pH of 9.30 with a very low buffering capacity (much like RO/DI, which has a low buffering capacity but is usually slightly acidic from dissolution of CO2.

In a very unscientific manner, I took a pint glass full of our tap water, added pH probe and a then a handful of fresh, premium NZ sphagnum... and watched the pH change INSTANTANEOUSLY from 9.34 to 6.32.

Just a fun factoid. My guess is these are all organic acids.

 

[Rick]

Chris

Have you checked out the recent thread I started updating basket culture?

Did a similar test (with similar results).

The test with fresh moss I did was prompted because I tested the water squeezed out of 1+ year exposed moss, and got much different results.

 

[ChrisFL]

No Rick, I didn't see that, but I just repotted, and have a bunch of old wet sphag. Let me see if I can replicate those results. Got a link?

 

[ChrisFL]

pH of 1.5 year old potted sphag water lowered the pH to only 7.61. Makes sense, all the acids have been leaching away since they are obviously water soluble.

 

[Rick]

Don't be sorry about duplicating efforts. Actually it's good that someone else came up with similar (independent) results.

You mentioned in my thread that you need to have balancing ions, and yes that is critical.

That is why I included hardness and conductivity data.

Note the hardness of the "squeeze" or interstitial water went up from about 20 to 400. This isn't trace metal being sequestered. That's all Calcium and Magnesium. Also conductivity won't substantially increase from "trace" metals. That all comes from the major ions which by default would be primarily sulfate, bicarb, and potassium since my well water is very low in sodium and chloride.

 

[ChrisFL]

Don't be sorry about duplicating efforts. Actually it's good that someone else came up with similar (independent) results.

You mentioned in my thread that you need to have balancing ions, and yes that is critical.

That is why I included hardness and conductivity data.

Note the hardness of the "squeeze" or interstitial water went up from about 20 to 400. This isn't trace metal being sequestered. That's all Calcium and Magnesium. Also conductivity won't substantially increase from "trace" metals. That all comes from the major ions which by default would be primarily sulfate, bicarb, and potassium since my well water is very low in sodium and chloride.

And the sulfate and bicarb are where all the alkalinity is coming from. That 190 number is insanity.

Now I wonder what controls the kinetics of this sequestration. In other words, did it max out its potential to uptake very early in the year, or was it a gradual slow process.

 

[Rick]

And the sulfate and bicarb are where all the alkalinity is coming from. That 190 number is insanity.

Now I wonder what controls the kinetics of this sequestration. In other words, did it max out its potential to uptake very early in the year, or was it a gradual slow process.

I think it depends on the concentrations/rates of what you put in. Which to me can be the scary part of this discussion. I've gradually (more or less) cut down the amount of fertilizer I've been using within the last 1.5 years. So I may have loaded the moss a lot faster initially than presently. This also works on the "leaky bucket" principal too. The plants themselves will use the stuff loading into the moss, but at a slow rate, and dependent on the light,temp, mass ratio of moss to roots. I believe that a component of the pot size/root loss problem is due to the above salt sequestration issues as well as the differences in water retention rates of varying pot volume:root mass ratios

This phenomena is pretty much the same for both CHC and bark. Orchiata comes preloaded with divalent cations so I think just takes longer to exchange to the monos and load up with anions.

 

[keithrs]

I wonder if adding humic acid to the feed water would help?