Ca and Mg again

[DarioU]

Dear Orchids friends, Excuse me for my bad English. I need to supplement my fertilization with Ca and Mg but How is not clear. I have read very much but the argument is not clear at all.
Can I supplement Ca and Mg only with Ca nitrate and Mg nitrate for a long time ?
Can I mix in the same solution, in the right doses of course, Ca nitrate and Mg nitrate?
Because both (Ca and Mg) are in their nitrate form perhaps I can mix them, I think.
Can add Ca nitrate and Mg nitrate in Fertilizing solution or I must keep them separate?
If I mix them with the fertilizing solution the P precipitate them resulting in P, Ca and Mg deficience?
I have read all and the contrary of all.
Thank you for your help and answers
Dario

 

[Brabantia]

You can mix Calcium nitrate and Magnesium nitrate in solution without problems.
The ratio Ca/Mg must be between 3 and 4. You can added this solution to your fertilyser solution by taking into account brought quantities of Nitrogen by Calcium nitrate and Magnesium nitrate. By using the usual concentrations in Phosphorus for Paph's (5 to 10 ppm or less) you will have no problems with Calcium phosphate precipitation.

 

[Ozpaph]

Every month instead of my usual fertiliser I use either a level teaspoon of magnesium sulphate (Epsom salts) OR Calcium nitrate to 5 litres of water and apply. My usual fertiliser does have both elements.

 

[DarioU]

Thank you very much

 

[Rick]

Why do you think you need to supplement Ca and Mg?

Also if you supplement with potassium more than 10 ppm, adding Ca and Mg is a waste of time since the potassium will block the Ca and Mg uptake even if you add Ca to more than 200ppm.

 

[Stone]

Also if you supplement with potassium more than 10 ppm, adding Ca and Mg is a waste of time since the potassium will block the Ca and Mg uptake even if you add Ca to more than 200ppm

Sorry but I must strongly disagree. If this were true, we would be seeing deficienies all over the place. It's pretty obvious that Ca and Mg will not get ''blocked'' with these K levels. As an exapmple, lately I have been feeding my 5 Phalies on cork 100ppm N and 80 to 100ppm K every day with no apparent problems. If Ca and Mg were getting blocked by the abundant K, there would be no root tips and much chlorosis in the leaf. On the contrary, leaf size and colour and root growth are better than last year when they were getting half that or less.
Yes the fact that they are on cork allows (and I would even say that for optimum growth, requires) that I feed higher rates but those K rates are still getting into the plant's system (as you know orchids have no trouble taking up K) as there is little or no flushing with plain water in between. So where is the blocking?
I estimate they get around 50 to 60ppm Ca as nitrate plus a little more from the water and 10 to 20ppm Mg after I've done the blending. There is absolutlely no apparent Ca or Mg deficiencies which I can see.

 

[DarioU]

Thank you for your answers. I need to supplement Ca and Mg because my well water has too much Na and so I use RO water. My fertilizer has very low content of Ca and Mg and I have some problems with buds. I use N/K about 3:1.

 

[Stone]

Thank you for your answers. I need to supplement Ca and Mg because my well water has too much Na and so I use RO water. My fertilizer has very low content of Ca and Mg and I have some problems with buds. I use N/K about 3:1.

Just do as Ozpaph does or put the Calnitrate and Magsulphate into your regular (diluted) fert mix and dilute until you're happy with the EC. If you're worried about diluting the trace elements too much you can use K-lite to mix with your regular feed as I do occasionally. In fact K-lite is very handy for that! It will make a regular high ammonium/urea/no Ca mix into potentially better fertilizer by reducing P and K (if you want to do that) and increasing Ca, Mg and nitrate and keep the minor elements fairly constant.

 

[Rick]

Sorry but I must strongly disagree. If this were true, we would be seeing deficienies all over the place..

I think we do see (subtle) deficiencies all the time and don't recognize it. I wouldn't have looked into K issues in the first place if everything was just hunky dory/ peaches and cream.

The Cornell work you entered into the discusion clearly showed Ca blocking (not to absolute 0) with K as low as 50 ppm with Ca around 200ppm.

Given that no acute deficiency symptoms were apparent in that short term study, probably points to hybrid phals being quite tolerant of extremely low tissue Ca, rather than the well documented physiological effect of K antagonism in plant tissues.
If you were to have compared those Phale tissue concentrations from the Cornell study to the tissue sample reference standards for tomatoes and cantaloupe the Ca concentration would have been considered deficient and you would have expected decreased crop yield. Comparing to corn standards, there was plenty of Ca, but overdose of K (so expected a yeild decrease from that).

Note we are talking yeild decrease and not acute trauma.

But anecdotally all my mounted phals are doing considerably better at daily K applications < 2 ppmK with Ca > 15ppm than when they got drenched weekly with the basic MSU rate of 100 ppm K with only 50 ppm Ca (RO water the rest of the week).

There's no doubt you can get a short term gain boosting K and phales seem to be exceptionally tolerant (especially in heavily selected hybrids). But 3-5 years down the road my plants experience burnout.

 

[DavidCampen]

... if you supplement with potassium more than 10 ppm, adding Ca and Mg is a waste of time since the potassium will block the Ca and Mg uptake even if you add Ca to more than 200ppm.

There is not scientific evidence to justify that statement.

 

[gonewild]

There is not scientific evidence to justify that statement.

Prove there is no evidence.

 

[Stone]

Prove there is no evidence.

No need!

 

[gonewild]

No need!

Nor is there a need to prove it to you, so quite asking for scientific proof.

The frequent, limited "there is no scientific proof" statements just confuse people that want advice about growing orchids rather than bio/chemistry.

 

[Stone]

Nor is there a need to prove it to you, so quite asking for scientific proof.

The frequent, limited "there is no scientific proof" statements just confuse people that want advice about growing orchids rather than bio/chemistry.

Hell I'm still getting confused on this issue. Some of Rick's observations are interesting and probably worthy of pursuing. Eg: the fact that his plants are doing well despite the very low K cannot be ignored. However there are the very same plants doing equally well with standard K. This points to the probability that big variations of potassium don't make much difference to the plant. There is ample evidence to the contrary of the above (Ca blocking) K statement yet only anecdotal observations and rather sketchy data (which can be easily countered) to back it up. As I see it, the weight of evidence is still massively on the side of K not being the problem it is claimed to be. A few studies have apparently found that after the optimum K was applied, increasing it made no difference in growth.

 

[DavidCampen]

Nor is there a need to prove it to you, so quite asking for scientific proof.

I ask for proof only because you and Rick keep making claims that it exists. Quit making claims that this potassium toxicity conjecture is anything more than a conjecture without scientific basis and I will quit pointing out that there is no scientific basis for this conjecture.

 

[gonewild]

I ask for proof only because you and Rick keep making claims that it exists. Quit making claims that this potassium toxicity conjecture is anything more than a conjecture without scientific basis and I will quit pointing out that there is no scientific basis for this conjecture.

This is not a science forum. This is a forum about growing orchids. This is not a plat form to prove or disprove anything.

What value do you add to the forum if all you do is say "there is no proof"?
Tell us about your personal experience or observations that might cause us to change our minds.

Personally I want to spend my time directly in contact with plants not googling for proof that does not exist to prove either side. There will never be scientific proof one way or another. But there is proof based on hands on experience.

So David what have you done towards using a low K fertilizer that has proven to you that it is a bad idea?

It would be much more enjoyable for 99% of ST members to read about other growers experience rather than arguments about scientific proof.

So again, seriously, have you had issues with your plants not growing well due to a lack of Potsassium?

 

[DavidCampen]

So David what have you done towards using a low K fertilizer that has proven to you that it is a bad idea?

I wouldn't use a low K fertilizer. It seems an absurd idea.

It would be much more enjoyable for 99% of ST members to read about other growers experience rather than arguments about scientific proof.

I would not disagree with that but someone who posts here and even in this thread; wrote a pseudo scientific article promoting his potassium toxicity conjecture in a way that would make it seem to the casual reader that he was offering scientific evidence that his conjecture was correct. And he continues to this day to make posts here, as recently as a couple of days ago, that would lead the casual reader to believe that there is scientific evidence for this potassium toxicity conjecture when there is not. I think that it would be great if certain people would quit trying to claim and imply that there is scientific evidence for this potassium toxicity conjecture.

So again, seriously, have you had issues with your plants not growing well due to a lack of Potsassium?

I don't use a low K fertilizer. I think that it is a patently absurd idea.

 

[Rick]

https://www.msu.edu/~warncke/E0486.pdf

Michigan State University seems to be pretty comfortable with the concept of K antagonism. Where's their proof or does MSU deal in pseudoscience?
(note this is a 1994 document, and K antagonism articles go back a lot farther than that)

They don't want to commit to any numbers except "do what you want as long as you don't go outside of the sufficiency standards"
(also note they use the term "toxicity" for exceeding the sufficiency standards at least once in this document)

The section on Mg is interesting in that they indicate that the soil equivalents of Mg must be equal or greater that of K and then Ca can be up to 10X greater than Mg.

The step I went beyond MSU was substituting the insitu (jungle) leaf tissue concentrations of NPK /Ca/ Mg for the agri-based sufficiency standards and extrapolating the eco-relevant concentrations of those nutrients into an application plan (that works).

 

[mrhappyrotter]

Oh dear baby Jesus. Do you want unresolved and heated 100+ comment threads? Because this is how you get unresolved and heated 100+ comment threads.

 

[Stone]

The step I went beyond MSU was substituting the insitu (jungle) leaf tissue concentrations of NPK /Ca/ Mg for the agri-based sufficiency standards and extrapolating the eco-relevant concentrations of those nutrients into an application plan (that works).

But the leaf tissue data or leaf litter data or throughfall data or Stemflow data or rainfall data or soil data or any other data does not have N at 10 times the K as K-lite does. I think this is an important point. Throughfall and stemflow are the major pathways for K so when it rains, soil water (terrestrial and epiphytic) is heavily charged with K. A paph growing at the base of a tree or in a bamboo grove or even in moss on a rock, which apparently many do, will have access to plenty of K, not in concentration, but in relation to other cations at that time (growing time).
So reducing the N in K-lite will actually get you closer to nature and ..... closer to a ''regular fertilizer. (except for the Ca)

http://www.biology.ufl.edu/COURSES/pcb5356/2010Spring/Kitajima/vitousek86.pdf