Paphiopedilum compost and calcium tolerance

[Rick]

but agree that primarily its the pH that is relevant here. But, you do agree that liquid in contact with marble would not stay acid for long?

Totally agree, that is the point of that little test I did with the aragonite in moss.

Seems like most of the debate may be caused by mixup in terminology. Or maybe you are thinking with a Norwegian accent and I am loosing track in my English

When you said that you saw no difference in using olivine instead of marble does that mean you (A) saw no positive improvement with olivine, or (B) or olivine was just as good as marble? (BTW olivine looks pretty much looks like the "serpentine rock").

If your answer is B, then pH/alkalinity for pot environment is indeed the parameter we are looking at.

I did see a comment in a previous post that said that seepages impacted by limestone are "nutrient rich". I can attest from testing well waters and seepages in limestone areas that they are virtually devoid of N and K. Some local systems have elevated P (maybe a few ppm at most). The bulk of the TDS is some mix of calcium and magnesium with varying amounts of sulfate, chloride, and bicarbonate. Also as you predicted with the roth example, the amount of TDS is highly variable depending on rainfall, contact time, and variations on the crystal hardness of the rock. Many seeps have very short contact times coming from shallow perched aquifers. Those waters generally have very low TDS compared to deep water wells pumped from under the same geology.

 

[Rick]

A useful cautionary with regards to negative interactions from excess Ca (besides the possibility of phosphate insolubility) is suppression of magnesium uptake at very high Ca.

For that reason I would prefer dolomite instead of aragonite (closer to 50/50 Ca/Mg), or supplement more Epsom salt in irrigation water if using a high % calcium buffer.

But overall I keep opening up the mix and pot (basket), and water more with more dilute solutions to see better results. This follows the roth example that you just discussed, that high rainfall over humus systems negates exposure to high TDS/pH.

 

[ALToronto]

Very interesting discussion. Just for giggles, how would all these results translate to a chemically inert, inorganic medium? I'm thinking lava rock and LECAs, both chemically similar. Do we need an organic medium, given all its problems in a closed, self-contained environment? Have people had success growing this way (and I'm not talking semi-hydro)?

 

[gonewild]

Its possible but I don't think you can assume that they cling to the limestone because they need or enjoy the lime because they also cling very well to polystyrene which contributes nothing towards nutrition I think.

Not trying to argue but.... polystyrene is not inert. It dissolves in water and releases chemicals. No one actually knows how it affects plant growth. It also has strong ionic charges.

And now get this part..... Polystyrene products are formed to shape in molds. The molds are sprayed with release agents which also coat the surface of the polystyrene products.......Calcium Stearate is used as a release agent.
So the polystyrene that the roots attach may be covered with Calcium.

 

[Bjorn]

Totally agree, that is the point of that little test I did with the aragonite in moss.

Seems like most of the debate may be caused by mixup in terminology. Or maybe you are thinking with a Norwegian accent and I am loosing track in my English

Guess you are touching it, different languages and mindsets. Mix that with terminology and there you are.

When you said that you saw no difference in using olivine instead of marble does that mean you (A) saw no positive improvement with olivine, or (B) or olivine was just as good as marble? (BTW olivine looks pretty much looks like the "serpentine rock").

If your answer is B, then pH/alkalinity for pot environment is indeed the parameter we are looking at.

The main reason for adding olivine was to check whether it could have some influence being an ultrabasic mineral closely resembling serpentine. While serpentine was unavailable, olivine was in my posession so... But the answer is not straight forward; the olivine was added to the marble mix without showing any significant differences to those without olivine. So its difficult to say anything except that the olivine does not contain any magic ingredient.

I did see a comment in a previous post that said that seepages impacted by limestone are "nutrient rich". I can attest from testing well waters and seepages in limestone areas that they are virtually devoid of N and K. Some local systems have elevated P (maybe a few ppm at most). The bulk of the TDS is some mix of calcium and magnesium with varying amounts of sulfate, chloride, and bicarbonate. Also as you predicted with the roth example, the amount of TDS is highly variable depending on rainfall, contact time, and variations on the crystal hardness of the rock. Many seeps have very short contact times coming from shallow perched aquifers. Those waters generally have very low TDS compared to deep water wells pumped from under the same geology.

if I said nutrient rich, then I meant richer in some nutrients that the limestone could carry. Typical would be some trace elements. Roth mentioned years ago that hangianum (or was it vietnamese?) was found on limestone near lead mines in northern vietnam. Things like that could be released by the dissolution of limestone by acid. Of courselimestone could act as a stabilising buffer fo phosphorus as well

A useful cautionary with regards to negative interactions from excess Ca (besides the possibility of phosphate insolubility) is suppression of magnesium uptake at very high Ca.

For that reason I would prefer dolomite instead of aragonite (closer to 50/50 Ca/Mg), or supplement more Epsom salt in irrigation water if using a high % calcium buffer.

But overall I keep opening up the mix and pot (basket), and water more with more dilute solutions to see better results. This follows the roth example that you just discussed, that high rainfall over humus systems negates exposure to high TDS/pH.

Guess that we could differentiate between those experiencing a dry season relying on seepage water from limestone, and those that gets rain all year (all except those from the monsoon areas?) I do expect that typical limestone-cliff dwellers like sanderianum and stonei also tolerates limestone well although they are not exposed to dry seasons. At least I have indications that they do.