Ca and Mg again

[Rick]

What makes the most sense, IMO, is to provide nutrients in roughly balanced proportions to plant requirements. If you provide adequate supplies of N, P, K, Ca, Mg, and S, the plant will sort out what it needs. Add in the micronutrients if you are using a mineral-deficient water source. Also, adjust pH so that plants can utilize the nutrients you are providing.

What are the plant requirements you are referring too?

Are you refering to sufficiency standards and if so which ones?

 

[cnycharles]

You mention that the 'plant will sort out what it needs', but some elements/compounds it takes it up whether it needs it or not, and then it has to deal with the excess. Previous multiple discussions about this point have already been hashed over here

 

[Stone]

You mention that the 'plant will sort out what it needs', but some elements/compounds it takes it up whether it needs it or not, and then it has to deal with the excess. Previous multiple discussions about this point have already been hashed over here

This is not a problem when you apply at the correct ratio and concentration.
Basically, plant growth is reduced when the first of any element becomes too high in concentration and it is also reduced when the first of any element becomes too low in constentration. Therefore the trick is to apply the elements at optimum or just below optimum to achieve the best performance. And this is where all the trouble starts :evil:

 

[Stone]

Your Vanda does this too. Every time it drops a leaf, sheds an old root, jettisons some old plant stem or a spent bloom or flower spike, your Vanda is "debulking". It is well known that this is the manner by which plants get rid of wastes. As such, a calculation such as yours is missing an important "exit" for K to leave the system. There may also be other ways for K to leave the plant (for example, I have no idea if extrafloral nectar, produced by many orchids, contains any K, but it might).

Yes. And another major way K is removed is through leaching. Every time you hose down your plant K is removed more than most other elements.
You can imagine how much is leached during 5 days of constant heavy rain but of course there must also be a balance between uptake and renoval.
But we don't really leach anything like a monsoon therefore K might not be as necessary in cultivation. That's one for Rick....Oh no!!!

 

[Ray]

Therefore the trick is to apply the elements at optimum or just below optimum to achieve the best performance. And this is where all the trouble starts :evil:

Ah yes, the "holy grail" or horticulture.

Nobody really knows what the "optimum" is for any plant, including major food crops like corn, and certainly not orchids. You apply something, observe the "performance" of the plant, then do tissue analysis to try to correlate them.

 

[Rick]

Yes. And another major way K is removed is through leaching. Every time you hose down your plant K is removed more than most other elements.
You can imagine how much is leached during 5 days of constant heavy rain but of course there must also be a balance between uptake and renoval.
But we don't really leach anything like a monsoon therefore K might not be as necessary in cultivation. That's one for Rick....Oh no!!!

Mike that doesn't make any sense. Epiphytic plants should have no K at all in them during the rainy season in that case, and that just completely negates all your argument that epiphytes get their K from stemflow and throughfall.

Leaching out of dead plant materia is something else altogether agreed.

Also with reference to loss of K from leaf drop, the Zotz work on Panamanian epiphytes showed readsorption of K from old leaves (before leaf drop) was somehere around 30-50%. P was recycled at roughly 60% while Ca and Mg where hardly recycled at all.

 

[gonewild]

Has anyone else located data indicating that orchids get applications of NPK at K concentrations >50ppm or even 25ppm?

I have made a lot of insitu tests now here in the Peruvian orchid zone.
I am not making chemical analysis to determine ratios of mineral rather taking simple ppm/ec and pH. But I am sampling actual water around the orchid root zone.

The below tests will give a direct clue about the quoted question.

Sample#1
Rainwater
ppm 0.0
pH 7.0

Sample#2
I collected moss samples from three separate but similar trees. Moss was taken directly from areas with orchid roots growing in on or through it. Many different orchid species are present including also ferns, pepperomias, and assorted other plants.
The samples were collected during a light rainfall in the "dry" season.
The moss was saturated and flowing with rain water that would represent "stem flow". I placed the samples directly into a plastic bag and allowed the water to drain off and tested this sample.

Free drained water was clear:

ppm 14.7
pH 6.6

I then squeezed the moss to collect all water possible:
Squeezed water was moss green color.

ppm 102.0
pH 5.9

Sample #3
Walking through a virgin forest at 1200m elevation I took equal moss samples from 50 different trees each sample was taken from a position the would receive the most influence from stem flow.

Free drained water was clear:
ppm 13.9
pH 6.2

I added just enough water to slightly over saturate the moss (after it had been drained. Soaked for 24 hours and squeezed to collect a sample.

ppm 119.0
pH 5.5

Sample#4
This sample is a random collection containing of orchid roots, moss, bark fragments and Lichens. All collected from the root zone of orchids.
This sample contained enough water that I made the sample by lightly squeezing the mass.

Water was slightly not clear:
ppm 108
pH 5.7

Sample#5

Stem flow water:
Collected from bark and leaves with very little moss or Lichen present.
This might represent a mid point between stem flow and through fall.

ppm 6.7
pH 6.9

Sample#6
Organic matter collected from tree crotch growing orchids:
Sample saturated with rainwater and allowed to stand 24 hours.

ppm 44
pH 4.8


Sample#7
Limestone rock face.
Water flowing over bare limestone, moss, ferns, begonias, aroids and through trailing tree roots. This water represents a Limestone formation.

ppm 8
pH 5.2 (yes that is correct)

 

[Rick]

And this is TDS (all salts) and not just K.

 

[Rick]

You can imagine how much is leached during 5 days of constant heavy rain but of course there must also be a balance between uptake and renoval.
But we don't really leach anything like a monsoon therefore K might not be as necessary in cultivation.

If leaching from live plants was significant it would end up downstream in creeks/rivers. The amount of K in creeks/rivers is generally down <5ppm

I managed to locate water chem data for creeks/streams in the karst areas of PNG where the giant bulbophyllum species are found (like under the waterfalls/caves/overhangs). Surface water K is down in low single digit ppms (just about like any karst derived river in the world).

Sadly this data came from an EIS conducted for petroleum industries looking to exploit the areas where these orchids come from.

 

[Stone]

Mike that doesn't make any sense. Epiphytic plants should have no K at all in them during the rainy season in that case, and that just completely negates all your argument that epiphytes get their K from stemflow and throughfall.

Huh? I said there must be a balance between uptake and leaching. ( perhaps ''balance was the wrong word) The leaching would only come from the leaf surface but obviously with a net uptake.

I have a paper which talks about intracanopy ''pulse nutrient release'' (wet/dry flux) It seems this is an important pathway for nutrient transfer. Treeleaf to moss to orchid to fern to lichen to moss to orchid and so on. The net uptake coming from rain, dust deopsits and tree leaf exudations (with the exeption of extra N from N fixing organisms). That's how you can start with a bare tree and eventually have it dripping with epiphytes. Those tiny twig epiphytes growing on the very outer edge of a tree would get most of their nutrients from dust disolved in rain or carried in the wind.

Quote from the Yunnan paper: ''The extent to which individual nutrients are leached appears to be dependent on the mineral nutrient status of the plant and the balance that exists amoung elements. Increased K content of throughfall indicates that the level of exchangeable K is related to the overall K economy within the foliage''
''Despite some variation, deposition ratios of K is high in all forests''.

The point is that K is very leachable and the main source of it in the canopy is from any and all green material.

 

[Bjorn]

I have read this thread with great interest, but to me -except for Lances last post - there are three groups that have their predetermined opinion and that try to knock down the opponents using whatever arguments that are available.
Rick and Lance firmly belive in low K, Mike (Stone) cannot accept the good results of Rick because orchids grow perfectly well with normal K-Levels, and then you have David and Catt Mandu that seems more hooked up on the formal deficiencies, as if we were writing scientific papers here.
Ok what has been the outcome of the discussion? In my opinion, anecdotal evidence (and that is good enough for me) has shown that orchids can be grown with low K, but it may not be necessary. There are strong evidence that they suffice with some 100ppm TDS in their water as well.
Orchid roots absorb cations in their velamen (might be so for paphs as well) so nutrition is highly dependent on the balance of nutrients and not so much on the concentration. Actually they do fine with very dilute fertilisers. If the balance is wrong, over time, malnutrition hits in ; much like people getting unhealthy from obsessive sugar intake (thik Rick used that one some time(years) ago). So, continous fertilising with very diluted fertiliser is one clue here.
Possibly, reduced potassium is a good thing as well. Many people use urea or ammonium based fertilisers and the kationic nature of these (NH4+) perfectly fits into the "active sites theory" of the velamen. Nitrate does not btw.
One thing that everyone except Xavier seems to ignore are the micronutrients.
Xavier (Roth) has repeatedly written that the Fe:Mn:Zn balance normally is more or less opposite to the chemistry of wild-grown leaves. You may find more on that in Xaviers thread on "Mineral Nutrition".
The reason why I mention this is that I noticed a growth spurt on my randsii seedlings once I sprayed with Dithane which is basically a manganese-zinc compound. Suddenly they started growing at the speed of normal paphs!
Might be a coincidence? Well that triggered me to look a bit further into this. Some of you may have noticed that many of my plants grow rather quickly. In hindsight, one of the variables in my growing has been that I have been using a rather special foliar feed as part of my fertiliser regime. This had been mixed 50:50 with K-lite. I did that because of yellowing with K-lite alone and so I thought that I needed Urea (which was 50% of the foliar feed). Checking up things revealed that the urea was not the only difference, the balance in the micros was also totally different. K-lite has Fe:Mn:Zn of 0.115%:0.077%:0.077% (approx 3:2:2)
while this foliar feed had Fe:Mn:Zn of 0.02%:0.26%:0.14% (approx 1:13:7)
Not only the balance, but also the levels were quite different.
And more in line with Xaviers findings on tissue analyses.
The 50:50mix produces a fe:Mn:Zn of 0.0675%:0.1685:0.1085% or roughly 2:5:3 balance.
Note that I have used less Fe and more Mn and significantly more Zn than I would with K-lite alone at a given TDS.
Sorry for the long post, though it was about time to share

 

[Stone]

If leaching from live plants was significant it would end up downstream in creeks/rivers. The amount of K in creeks/rivers is generally down <5ppm

Perhaps but this data is only relevent to me if you provide the ppm for total N, P, Ca, and Mg as well and preferably from a place where orchids grow.

 

[Stone]

I have made a lot of insitu tests now here in the Peruvian orchid zone.
I am not making chemical analysis to determine ratios of mineral rather taking simple ppm/ec and pH. But I am sampling actual water around the orchid root zone.

The below tests will give a direct clue about the quoted question.

Sample#1
Rainwater
ppm 0.0
pH 7.0

Sample#2
I collected moss samples from three separate but similar trees. Moss was taken directly from areas with orchid roots growing in on or through it. Many different orchid species are present including also ferns, pepperomias, and assorted other plants.
The samples were collected during a light rainfall in the "dry" season.
The moss was saturated and flowing with rain water that would represent "stem flow". I placed the samples directly into a plastic bag and allowed the water to drain off and tested this sample.

Free drained water was clear:

ppm 14.7
pH 6.6

I then squeezed the moss to collect all water possible:
Squeezed water was moss green color.

ppm 102.0
pH 5.9

Sample #3
Walking through a virgin forest at 1200m elevation I took equal moss samples from 50 different trees each sample was taken from a position the would receive the most influence from stem flow.

Free drained water was clear:
ppm 13.9
pH 6.2

I added just enough water to slightly over saturate the moss (after it had been drained. Soaked for 24 hours and squeezed to collect a sample.

ppm 119.0
pH 5.5

Sample#4
This sample is a random collection containing of orchid roots, moss, bark fragments and Lichens. All collected from the root zone of orchids.
This sample contained enough water that I made the sample by lightly squeezing the mass.

Water was slightly not clear:
ppm 108
pH 5.7

Sample#5

Stem flow water:
Collected from bark and leaves with very little moss or Lichen present.
This might represent a mid point between stem flow and through fall.

ppm 6.7
pH 6.9

Sample#6
Organic matter collected from tree crotch growing orchids:
Sample saturated with rainwater and allowed to stand 24 hours.

ppm 44
pH 4.8


Sample#7
Limestone rock face.
Water flowing over bare limestone, moss, ferns, begonias, aroids and through trailing tree roots. This water represents a Limestone formation.

ppm 8
pH 5.2 (yes that is correct)

All very interesting Lance and thank you. However it tells me nothing about what and how I should feed my orchids. Only that they get low concentrations of everything which we already knew.

 

[Stone]

Mike (Stone) cannot accept the good results of Rick because orchids grow perfectly well with normal K-Levels

That is not accurate Bjorn. I have acknowleged that Rick's plants (the paphs in baskets which I have seen are doing well and in some cases very well)

I am trying to point out that 1. K is not toxic to plants in all kinds of concentrations. 2. That K does reduce Ca and Mg in high levels but that the consentrations commonly used in horticulture does not interfere with plant growth. 3. That there are countless examples of these orchids doing equally well with K concentrations as high as the N given to them. 4. That from all the reserch I have seen from habitat that K is generally close to N in stemflow cheimstry (sometimes much higher)and that if you are to follow natural ratios, the K in K-lite would be too low.
Its a very handy fertilzer to mix with others though.

 

[Stone]

.

One thing that everyone except Xavier seems to ignore are the micronutrients.

Bjorn, we do not want to ignore the micro nutrients. However there is almost no data which I can find pertaining to micronutient ratios in orchid habitats.
Remember that the constentrations of these are usually so extremely low that it must be difficult to analyze what is there or probably regarded as insignificant by the reserchers.
The leaf tissue data supplied by Xavier is very interesting but incomplete without the habitat data to compare.
Having said that, I have another Wang paper which analyzed micros in Phal leaves after giving 4 different fertilizers:
10-13.1-16.6
20-8.6-16.6
20-2.2-15.8
2-0.4-1.7
Micros in the fertilizers are not mentioned however we can probably assume they were ''standard'' with Fe being higher that Mn and B. as they were commercially available fertilizers. Or perhaps were not even included??

As an example, the leaf concentratons after the experiment in mg per kg dry weight for the first one was:
Mn 433, Fe 24, Na 3488, (must have used high NaCl water?) Cu 4.6, B 35, Mo 1.24, Al 50, Zn 14.5.

Ratios from the other fertilizers are similar.

Take from that what you will but it is obvious that what is given is not necessarily taken!

 

[Bjorn]

Agree Mike, what you give is not necessarily what is consumed. In most cases the bulk of the fertiliser drops directly onto the floor.
If we accept the suggestion that the velamen of the orchid roots contain active sites that captures the nutrients of the water coming (Zotz and Winkler, Oecologia (2013) 171:733–741), then the proportions must have significance for the uptake. Then, if the sites get occupied by e.g. Fe it will be on the expense of other, more needed nutrients.
A too high amount of the wrong ion may thereby block uptake of other essential nutrients.

 

[Ray]

One thing that really urinates me (pisses me off) about Bjorn's post is his apparent inability to break his comments into readable paragraphs!

That aside - what makes you think the nitrate ion is not trapped by the velamen?

 

[Bjorn]

See what you mean Ray; hardly readable right? I'll try to improve.
Below I put up some more speculative assumptions trying to explain a bit how and why

Then your question about nitrate; no proof for this, but most nutrients are cations (positively charged), and I just assume that the bonding mechanism in the velamen is of electrostatic nature. E.g. many ceramic raw materials have negative surface charges.(negative zeta-potential although not exactly the same) Cellulose is another material that normally is negatively charged, and that may be more relevant in this context.

To grab kations by electrostatic attraction, negatively charged sites must be present, so unless you have special (=positively charged) sites for anions (which might be present of course) they will not get electrostatically attracted.

Another thing is that to be used by the plant for aminoacid production (aidied by nitrate and nitrite reductase) the nitrate has to be reduced, whilst ammonium is already in the reduced state and should therefore be readily available.

 

[Ray]

OK, but an NO3 ion is negatively charged....

 

[Rick]

I have acknowleged that Rick's plants (the paphs in baskets which I have seen are doing well and in some cases very well)

I'm hurt Mike

Didn't you like my Maxilaria tenufolium

That's in a pot

And SlipperKing has been garnering a lot of awards with his plants (mostly in pots) since going low K.

Emydura has his own version of low K which seems to be producing some amazing results.

I don't think its the baskets for anything other than it reduces the overall exposure to fertilizer (like a mounted plant).

But my mounted plants have also improved. (Didn't you like my Phalae pallens?)