Silicon the forgotten macronutrient?

[ALToronto]

Very interesting K-lite discussion, but I cannot understand the drama it is causing. Come on, guys - try it or keep doing what you've been doing. Some people are having success with it, that's great. It may be the silver bullet or it may not, there are too many other interdependent factors that affect the overall health of our plants. No need to get riled up over the theory of people who have done a lot of thinking in formulating it (and the fertilizer itself).

The next steps perhaps should be tweaking the formulations for different genera or growing conditions? This can get downright silly, and very impractical.

I'd like to steer this discussion back to silicon and soluble, bioavailable silicates. I'm a relative newbie (I grew orchids 20-15 years ago but had to give them up due to frequent business travel), having just gotten back to growing them.

So take my musings for what they're worth, but I keep thinking about agar-agar. There is a reason it's used to germinate seeds, and I suspect part of that reason is that it contains a lot of soluble silica. Has anyone tried adding small amounts of it to water - not nearly enough to gel, but enough to supplement? Would seem like an easy solution to the silica deficiency problem - any thots?

 

[Rick]

So take my musings for what they're worth, but I keep thinking about agar-agar. Has anyone tried adding small amounts of it to water - Would seem like an easy solution to the silica deficiency problem - any thots?

How much silica is in agar? Since it is a marine algae (kelp product) is it more concentrated in silica than the kelp extracts that many of us already use, that I already suggested?

I don't think I've experienced any symptoms that I could say are caused by silica deficiency. I'm not even sure if anybody is actually experiencing silicon deficiencies. There is a product called Pro-tekt that is essentially potash solution with high silicates, that folks have been playing with for years.

http://florawww.eeb.uconn.edu/msds/Pro-Tekt_DataSheet.pdf

I've used it too for all the symptoms that I have later attributed to excess K, and as noted in previous posts many of us didn't get any positive culture effects from use.

Now the above data sheet claims scientifically proven to get Si into plants, and there appears to be some actual leaf concentration measurements, but Bjorn says that the potash silicates are not bio available.

So I don't know????

 

[ALToronto]

There is a big difference between the potassium silicate in Pro-Tek and the silica contained in plants. Metal silicates, where the silicate ions are bound to the metal oxides (K2O, Na2O, CaO, etc.) are all characterized by very high pH, since the same metal oxides in water form their respective hydroxides. Potassium silicate in Pro-Tek has the lowest molar ratio of K2O:SiO2 I've ever seen (and this ratio is variable, easily increased by adding the metal hydroxide, but not easily decreased), and the reason is to minimize the alkalinity and maximize the SiO2 concentration. However, it is still very alkaline. I wonder how much thought really went into making it - I suspect that someone at Dyna-Grow read about silicon being beneficial, so they came up with the simplest inorganic product that delivered it (about 50 cents' worth of an active ingredient in a quart of distilled water).

Plant-derived silica is a different product altogether, with no alkalinity issues and a different chemical form. It's sold as a health supplement for people, to strengthen hair, skin and nails (and it works, at least for nails!). I don't know how much silica agar-agar contains, and perhaps not as much as the kelp extract that I also use. But there was a discussion on another forum that hormones should not be used continuously, and that they are more effective if the plants are given a break. Is that the case with silica supplementation too? Should we be looking at another source when we're not using kelp extract?

 

[Rick]

Should we be looking at another source when we're not using kelp extract?

How do you account for Dynagrows results of silica actually going into plants via Protekt? I don't think they really came up with anything new. Humanity has used soaked wood ashes for potassium (and at least incidentally) for silicates for hundreds of years.

There is silicates in the various organic and inorganic potting media we use.

Most of us aren't worried about using low doses of kelp for years on end, so I don't feel I need to look for an alternative without kelp, I still have not heard of any symptoms of silica deficiency in orchids, that require special need for supplementation.

I'm not trying to convince you to not try special silicate supplements for your plants. So you are welcome to come up with whatever you'd like to try and tell us about it when it works?

 

[Rick]

Should we be looking at another source when we're not using kelp extract?

I guess another way to phrase the question is why do we always suspect that our plants are starving for something other than water and carbon, when the NPK, CaMgS Si B.......makes up less than 5% of the total plant.

Can you find any literature that indicates that soluble or bioavailable Si in the orchid environment is found at the concentrations that you are suggesting is necessary for their survival? I couldn't find any evidence for bio available potassium in the orchid environment at much more than 1ppm. That's why we looked at K as a toxicity issue rather than a starvation issue.

 

[Bjorn]

I cannot find any analyses of silicon in the orchid environment; but that does not mean that it is not present. For orchids like paphs, that live as humus epifytes or lithofytes silicon should be readily available in the seepage water. For epifytes a not insignificant amount comes with the rain as dust. E.g a lot of the nutrition of the Amazonas is carried over as mineral dust with the trade winds from Sahara. Under any circumstance, the fact that plants contain silicon, means that they absorb it. And it is mainly absorbed as monosilicic acid. And it is absorbed in quantities that sometimes is higher than any other mineral(N, water and C exempt) in the plant. Normally at modest levels comparable to those of e.g. Phosphorous and potassium (K)
In this ref.
http://horttech.ashspublications.org/content/20/3/603.full.pdf
the effect of silicon fertilization is investigated for phalaenopsis grown in sphagnum. They have used K-waterglass so obviously it works (even if I claim that it does not) at least to some extent. The addition levels they used were rather high so perhaps it is not that effective:evil:
However, silicon levels increase with fertilisation, as does growth.
Taken the normally low amount of silicon available as silicic acid, the roots of the plants must be extremely effective in absorbing it, so most people probably never see any deficiency symptoms. There is always some in the water, e.g. in well water, and the compost. And also it seems as if low levels of silicon does not give any severe deficiency symptoms, but silicon aids in the general uptake of many other nutrients like P, moderates uptake of other potentially poisonous elements (Mn, K etc) and so on. Additionally it is known to strengthen the epidermis of the cells rendering them less vunreable to attack by pests and deases. All in all I believe that the most prominent role of silicon is to strengthen the "immune system" of the plant resulting in healthier plants that tolerate stress better ; perhaps with a faster growth. But this is just my impression.:rollhappy:
Btw. there are thousands of publications out there dealing with silicon in plants. Not many on orchids though.

 

[ALToronto]

I plan to try growing in chopped hemp stems, which is a very good source of bioavailable silica. I will report on my progress.

 

[Rick]

I plan to try growing in chopped hemp stems, which is a very good source of bioavailable silica. I will report on my progress.

Horsetail is a plant very high in silicon, and may be available in wetter areas where you live.

 

[Rick]

Btw. there are thousands of publications out there dealing with silicon in plants. Not many on orchids though.

Thats what I noticed too.

Another math exercise would be to take the silicon in leaf litter in my article and work it backwards to possible terrestrial exposure.

 

[gonewild]

Is Silica and Silicon the same element?

 

[cnycharles]

quick net search listed silica as being a somewhat generic term for 'silicon dioxide'. some might be using the word interchangeably with silicon, but one is a compound and the other the element

that said, years back I tried pro-tekt and hadn't seen much change in my plant growth. at the time I had read somewhere that a study I think with orchids didn't show a whole lot of difference in plants that were given it to try and toughen them up, though greens grown hydroponically may have taken it up more but too much seemed to make them or a few other plants a bit brittle. now, if that isn't a pretty indefinite statement I don't know what is! (meaning the lack of complete memory about it) so I tried pro-tekt but decided it wasn't the limiting factor in my growing (and since then have decided that it mostly was myself)

 

[gonewild]

OK then we should decide which we are talking about Silica or Silicon. One an element and one a compound.

Do plants contain Silica or Silicon in their tissue?

What are you applying in the form of a nutrient, silica or silicon?

Do plants need Silica or Silicon?

 

[Bjorn]

The -a ending is used for oxides like silica for silicon dioxide , alumina for aluminiumoxide, titania for titaniumoxide urania for uranium oxide etc. The plants absorb a hydrated form of silica that we call monosilicic acid. That is silicondioxide that has reacted with two water molecules into a weak acid. Once inside the plant, the monosilicic acid polymerizes and become; guess what? Silica! So I guess it is fair to say that silica is what we talk about in plants. When we analyze the chemical components, it is however normally the element we analyze, but for practical purposes it is often reported as the oxide.

 

[gonewild]

How do plants absorb monosilicic acid? Through roots, foliage or?

Once inside the plant and the monosilicic acid polymerizes into Silica what does the plant do with it? Is it floating around as free silica or combined into another compound making up a part of tissue?

 

[ALToronto]

It goes to the outer membranes (velamen and 'skin' on stems, pbulbs and leaves) and makes them stronger - presumably, tougher for insects to chew through. Also less likely for molds to find a vulnerable site to infect.

 

[Rick]

It goes to the outer membranes (velamen and 'skin' on stems, pbulbs and leaves) and makes them stronger - presumably, tougher for insects to chew through. Also less likely for molds to find a vulnerable site to infect.

In forage plants on the plains grazed by big herbivours high silica was an adaptive feature. But high silica is not universal for many plants. I attached an article early on that showed that a lot of flowering plants tended to be on the low side of Si. Also Ca is responsible for a lot of cell wall integrity issues that effect diisease and pest resistance.

Since high K inhibits the induction of Ca and Mg, I wonder if it does the same thing to silica.

 

[Ray]

quick net search listed silica as being a somewhat generic term for 'silicon dioxide'. some might be using the word interchangeably with silicon, but one is a compound and the other the element.

In the world of ceramics, the "-a" is often added to a metal to indicate its oxide - silica and alumina being the most common.

I do not think any plant or animal can take up silicon dioxide readily, and if we see SiO2 in the plants, it was likely formed there. I could be wrong.

 

[gonewild]

It goes to the outer membranes (velamen and 'skin' on stems, pbulbs and leaves) and makes them stronger - presumably, tougher for insects to chew through. Also less likely for molds to find a vulnerable site to infect.

How does it move in the plant to the outer membranes?
Is it deposited as layers of Silica?

 

[gonewild]

I do not think any plant or animal can take up silicon dioxide readily, and if we see SiO2 in the plants, it was likely formed there. I could be wrong.

I happen to agree but......
In tropical South America the "local" timber cutters don't like to cut trees growing on sandy soils because they say the trees contain too much sand in the wood and it dulls their saws. They say the trees suck up the sand grains for the first 2 logs and then it won't go any higher. Now this might sound a little strange but the wood is high in silica as they say. Obvious the trees are not sucking up grains of sand but there are Silica deposits throughout the wood.
I really would like to understand why these trees have silica deposits.

 

[ALToronto]

How does it move in the plant to the outer membranes?
Is it deposited as layers of Silica?

I don't know the exact transport mechanism, but in animals and humans it tends to strengthen hair, skin and especially fingernails. At least that's where I saw the biggest improvement when I took supplements. I stopped taking them because they improved ALL the hair, all over the body, especially in places I didn't care to have it improved.