# Silicon and its role role for plant health



## Bjorn (Apr 8, 2013)

*Silicon and its role for plant health*

In my professional life I have frequent contacts with scholars and scientists working with metallurgical and inorganic chemistry. Sometimes I even stumble into fields that are closer to my passion, orchid growing. A few days ago I had the pleasure to meet a prominent professor of the Russian Academy of Science that has spent the last 25 years investigating silicons role in plant nutrition. He showed us results from silicon fertilisation in Russia, China, Australia, USA covering a range of crops and results. Some of these tests were performed on large crops, like 5000 hectars of sugar-cane, citrus plantations in Florida, rice in China etc. Most of the results focused on the fact that silicon fertilisation improved the plants resistance to stresses. There are basically two ways it may happen, i) by improving the plants armour and ii) by improving the plants internal "pesticide production". The first is easy to understand and has been known for many years, the latter is a bit more "chemical" in nature.
To fight stresses (like attacs by fungii or insects) the plants synthesise a range of chemical compounds, that can be non-specific antioxidants or stress-proteins. The latter being "targeted" towards particular stresses like e.g. insect attacs. The role of the silica is as catalyst for the production of these compounds. Silica gel is a well-known catalyst in many types of syntheses in organic chemistry. By depriving the plant of silicon, the immune system suffers and they not only get more prone to infections, but also less able to stop the infection. BUT they grow, and if kept free of infections, nothing is noticed. And if they get an infection, well we all knows about those lethal erwinia/phytophora etc. infections...
This link is to an essay that sums up many of these things, although more has become known the last 3-4 years (the paper was written in 2009)
http://www.nutricaodeplantas.agr.br/site/downloads/unesp_jaboticabal/epistein_ann_appl_biol.pdf
Some you you may have noticed my scepticism to using alkali-silicate solutions as silicon fertiliser. The reason is that in those solutions the silicon is present as polysilicic acid which is not absorbed in an efficient way by the plants. The silicon should be as monosilicic acid that can be obtained by solution of silicates and amorphous silicon dioxide. DE is one the most common silicon fertiliser and is used in large quantities in sugar-cane fields in Australia. In Japan slags (mainly calcium silicate) are much used as silicon fertiliser. The silicates have a liming effect so should not be used in orchid composts. DE should not influence pH much and should be ok for orchids.
B


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## ALToronto (Apr 8, 2013)

Thanks for posting the paper - very interesting and readable, too. Do you mean diatomaceous earth as a source of plant-available Si? How readily does the Si in it dissolve in water?

Both rice and hemp are high in Si, and the stems and leaves of both crops are usually burned in order to fertilize the soil for the next crop. Is anyone selling rice hull ash or hemp ash as a horticultural amendment product? Silica gel is available in health food stores as a supplement, but it's unreasonably expensive. Does aloe vera gel contain silica?

Personally, I will be amending my orchid media with shredded hemp stems and fibres, but I also heard that they rot very easily. Definitely something to consider - we all want strong plants, and clearly, alkali silica products such as Dyna-Gro's ProTek are not appropriate.


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## ALToronto (Apr 8, 2013)

I just checked my soaking hemp fibres - I had put a small amount in a cup and just covered with RO water, about 50 ml. I did this on Friday, and checked them just now. The pH has dropped from 7.5 to 6.8 (and I still can't understand why the pH of my RO water is higher than the pH of my tap water, but that's another story). I don't know if this drop is due to decomposition of the fibres or simply carbonation of the water, or a bit of both.

The interesting reading is TDS. My RO water is about 15-18 ppm out of the tap, and this one read 185. I would bet a good portion of that is due to silica, and what concerns me is that it all seems to come out right away. I wonder how long it will take to deplete the fibres.


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## Bjorn (Apr 8, 2013)

I do not know about remedies available, but have some knowledge of rice hull ash. If it is burnt the traditional way, at low temperature it is a good source of silicon, but industrial burning normally yields temperatures so high that the silica becomes unavailable. About hemp, I do not know anything but possibly. The TDS readings appear high though.
B


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## papheteer (Apr 8, 2013)

I heard pool filter sand is a good source of silicon. Does anybody use it?


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## gonewild (Apr 8, 2013)

papheteer said:


> I heard pool filter sand is a good source of silicon. Does anybody use it?



You might be confusing pool filter sand with pool filter Diatomaceous Earth?


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## Bjorn (Apr 8, 2013)

papheteer said:


> I heard pool filter sand is a good source of silicon. Does anybody use it?



Sand is mainly silicon dioxide and contains as such some 50% silicon, but is not particularly soluble. Although sand is used in compost mixes its role is mostly as a structural element, although it cannot be ruled out that it may contribute somewhat with soluble elements. Soluble silica is quite scarse and its origin is commonly the decomposition of organic matter, silicates and non-crystalline silicon dioxide. DE is probably the easiest available of the soluble silicas.
I am using sand in my mixes, but not as silicon source.


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## Bjorn (Apr 8, 2013)

gonewild said:


> You might be confusing pool filter sand with pool filter Diatomaceous Earth?



the latter could perhaps be used
I am not familiar with it though.


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## gonewild (Apr 8, 2013)

Bjorn said:


> the latter could perhaps be used
> I am not familiar with it though.



I assume what you refer to as DE is Diatomaceous Earth?
Sediment composed of almost pure Diatoms?


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## Bjorn (Apr 8, 2013)

gonewild said:


> I assume what you refer to as DE is Diatomaceous Earth?
> Sediment composed of almost pure Diatoms?



Sorry, youre right should have written that. Its diatomaceous earth, and as such not very exotic.
B


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## SlipperKing (Apr 8, 2013)

So Bjorn how do you apply the DE to your plants?


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## Bjorn (Apr 8, 2013)

I do not add DE to my plants. Instead I add a submicron non-crystalline silicondioxide powder that I have acess to through my job. It is similar to DE although a bit more powerful as a source of silicon, in that it dissolves into monosilicic acid at a higher rate. Kind of nano-powder if you like. Not easily available for most thats why I talk about DE which has a better documented effect. It can be added to the compost or as I do, as a slurry into the irrigation water. The latter requires a certain fineness of the powder though.
I am uncertain about the effect of it, certainly not negative, but how do you assess the incident rate of a higly variable thing like e.g. Phytophora? Without a double blind test performed on a high number of similar plants? That gets too elaborate for me. 
B


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## Brabantia (Apr 8, 2013)

One of the best sources of silica is the obtained tea by making wallow plants of horsetails in some rainwater. It is what is used here in Europe in biodynamic culture to strengthen a plant's resistance to diseases infection.
Ref Click Here see chapter ROSE BLACKSPOT.


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## DavidCampen (Apr 8, 2013)

Bjorn said:


> I do not add DE to my plants. Instead I add a submicron non-crystalline silicondioxide powder that I have acess to through my job. It is similar to DE although a bit more powerful as a source of silicon


Is it a fumed silica?


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## Dido (Apr 8, 2013)

you can buy it reay in germany, but the tag says rich on K so it is against the K-lite discussion


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## SlipperKing (Apr 8, 2013)

Great article Brabantia! A couple of good laughs as well!


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## SlipperKing (Apr 8, 2013)

Dido said:


> you can buy it reay in germany, but the tag says rich on K so it is against the K-lite discussion



Which one? DE or Bjorn's stuff?


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## Dido (Apr 8, 2013)

horsetail extract I was meaning


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## ALToronto (Apr 8, 2013)

I use industrial quantities of silica fume, both grey and white, as well as colloidal silica. Would any of these be suitable? In what quantities? Grey silica fume is contaminated with carbon, but that shouldn't be a problem if it is otherwise suitable for plants. All of these forms of silica are amorphous and consist of single-digit-micron-sized particles.


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## Bjorn (Apr 9, 2013)

DavidCampen said:


> Is it a fumed silica?





ALToronto said:


> I use industrial quantities of silica fume, both grey and white, as well as colloidal silica. Would any of these be suitable? In what quantities? Grey silica fume is contaminated with carbon, but that shouldn't be a problem if it is otherwise suitable for plants. All of these forms of silica are amorphous and consist of single-digit-micron-sized particles.



you can probably use both fumed silica and silica fume. Uncertain about colloidal silica. Silica fume can be used, and that is what I do. Some qualities are >95% SiO2 with potassium lower than 1%. So I do not think that this tiny potassium causes problems in your K-lite attempt. Actually since the silica contains all kinds of trace impurities in a slow release form, the impurities may even be beneficial. I see you are familiar with concrete Al?.


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## ALToronto (Apr 9, 2013)

Bjorn said:


> I see you are familiar with concrete Al?.



It's my other 24/7 obsession. Unlike orchids, it earns me money. Sometimes they coincide.


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