I'll preface this post with I might not have fully understood what I was reading as it can be hella complicated but I think it's correct.
I'm in need of buying some more silicon and I was researching on what to buy. Following on from a post by Bethmeg a few weeks ago I've been doing some research. No question of course, silicon is a benefit no question so it's not a post about that.
What I've found however is that there are effectively two main and one seeming outlier sources of silicon used in horticulture. They are
"Traditional Silicon". This is a silicon in the form of potassium silicate (K2SiO3) or other metal salt
"Mono Silicon" - Often called Monosilicic acid and aka orthosilicic acid (SiOH4)
"Silicon nanoparticles aka Colloidal Silicon". This is the latest type of silicon that I can only find one provider of for plants (usually SiO2 nanoparticles)
So lets go through a bit of a silicon 101 first before going into each form in turn
Silicon is what is known as a "non vital beneficial". What that means is that unlike potassium, nitrogen and phosphorous and a handful of trace elements, the plant doesn't NEED it to grow however it still provides a lot of benefits. The only form of silicon a plant can absorb is in the form of silicic acid (primarily SiHO4) and, from what I understand, this is due to the size of the silicon molecules being too big to penetrate cell walls when it's in any other form. All silicon products boil down to providing silicic acid in some form or another and I will detail those below. There's 100's of sites and articles dedicated to explaining why silicon is so beneficial and I'll leave it to you to jfgi
There's a huge amount of chemistry around on all the different form of silicon but for this discussion you only need to worry about silicic acid.
Traditional Silicon Salts (e.g. Potassium Silicate)
Traditional silicon salts such as potassium silicate (and lesser used forms like sodium silicate) are used in a wide array of silicon supplements from many nutrient suppliers. Potassium Silicate is a powder that readily dissolves in water to provide a suspension of potash (potassium) and silicic acid. Most manufacturers will clearly label these salts on their products but it's usually much easier to tell they're using a silicate salt by the cost - 1l will typically be in the $10-25 (£8-20) range. If they're supplying to Europe (not sure of US regulations) you should always see Potassium Silicate and its concentration listed on the label as it's actually a potassium source and must be listed by law. My bottle of silicon from Shogun nutrients states it's 6% potassium silicate. The other tell tale sign is a high PH (typically in the range of 11-13) making it a very alkaline liquid. There are literally 100's of products on the market that use this method to deliver your silicon and it's the method that's been around the longest.
Monosilicic Acid
Sometimes also known as orthosilicic acid this is a relatively new innovation(20 years or so). Historically, silicic acid was not readily stable in water and so synthesis of liquid silicic acid that was stable as a liquid just wasn't possible as silicic acid readily polymerises and turns into gel. In the last 20 years new synthesis and mass production became possible that created a stable mono-silicic acid that remains liquid and didn't require chelation (addition of a metal to form a salt) to remain stable. A general sign that the product uses a stable Monosilicic acid is that PH is much lower (seems to be 9-10PH where reported) and the cost is much higher (typically 1l will be $50-60 (£45-55)) but some of the really concentrated versions (40%) will be up to $230 (£200) a litre! It will also be shouting from the rooftops it's a monosilicic acid of course.
Colloidal Silica (nanoparticle silicon)
So the substance that started me off on this bit of research, Colloidal Silica and more specifically Buddhas Tree - Solar Green Power. Full credit to @Bethmeg for the tip off in a thread where we were discussing the PH of normal silicon supplements. She made the bold claim that her silicon supplement didn't raise the PH and was PH neutral. Not being one to ever blindly trust anyones "trust me bro" posts (sorry Bethmeg!) I disappeared down this rabbit hole. Turns out she was both right (in the way that matters) and wrong (feeding my ego). Solar Green Power isn't in fact neutral, it has a PH of 9-10 making it weakly alkaline however remembering PH is logarythmic, not linear means it's 100-1000 times weaker than traditional potassium silicate. It also has the benefit of being added in much smaller quantities than traditional silicate salts so any increase in PH is going to be below detection range. So she was 100% right but so was I (and you know us men, being right is whats important)
After finding out about this stuff they mention in some of the information that it's a "colloidal liquid silicon fertiliser" which seems to be a different form of silicic acid than the "simple" monosilicic acid (SiOH4) that many other manufacturers are selling. So after a ton of reading in a nutshell it's an amorphous suspension of Si02 particles. What this means is that they effectively turn SiO2 into nano particles of varying sizes that are small enough to simply suspend themselves in water. These nano particles are then small enough to be able to slip through the cell walls and provide silicon to the plants. Or at least that's the theory they promote only I can find no research papers or information that it's true.
Firstly when I looked for manufacturers of colloidal silicon there only seem to be a couple of them globally mass producing it and neither of them mention its use as a horticultural supplement. Secondly a few research papers mentioned it being just another form of monosilicic acid while one other made a very clear distinction between the two forms. None discussed the use of colloidal silicates in horticulture. None of the other monosilicic acid providers I checked seem to mention anything about colloidal silica either. Lastly mass production seems to have been a very recent innovation (talk of it only being a process for about 10 years and only really growing in capacity over the past 5). This might explain why I can't find hardly anything about it.
Benefits, Conclusions and Questions (aka TL;DR)
I found a chart in my initial research which I can't find now that stated traditional silicon salts like potassium silicate will take weeks to months to be available to your plant and Monosilicic acids will be available in days. I can't find that chart now unfortunately but it's repeated on a number of sites. The other issue with potassium silicate based nutrients is that they push the PH up. This is bad for two reasons. First your PH in most setups should be between 5.5-6.2 for hydro and between 6-6.5 for soil so you always have to balance. Secondly mixing potassium silicates are a pain as if the PH of the liquid is above 8 when you add your other neuts you run the risk of your other nutrients binding to the silicon and separating. So when you add potassium silicate you have to add it first, drop the PH below 6.5 using a PH down and then add the rest of your nutes.
But the bottom line is if you currently use any form of silica salt (such as potassium silicate) supplement, I'd seriously consider at the very least a mono-silicic acid form of silicon. There's a lot of them out there and while they're a larger cost up front you need to add a LOT less and it's almost immediately available. I've not researched which is the better brand yet (as concentrations vary considerably) but I'm sure they're all much of a muchness.
As for Solar Green Power - @bethmeg and her grows speak for themselves so who am I to argue? However I'm not wholly convinced about the science behind the product if it does indeed, differ at all. It's the only product I could find proclaiming to use colloidal silicates and that always rings alarm bells but it might just be marketing speak for what is actually a pretty standard mono-silicic acid. The horticulture industry is heavily science based where crop maximisation tends to mean if something was THAT new and THAT revolutionary it would already be being used in high quantities for commercial crops all over the place. Instead the only reference I could find was from a small, cannabis focused, UK company that produces the stuff. To be absolutely clear, I'm not in any way saying it doesn't work, or doesn't work better than everything else out there, I just have no proof or information that it's the case. Not least as there's next to no information on their website apart from generic marketing information.
So there you have it. Happy to discuss or, if I can, answer any questions.
Incidentally I'm not sure which one I'm going to buy yet but it's definitely not going to be one based on a chelated silicate such as potassium silicate.
Cheers
MJ
N/B JUST before pressing "Submit New Thread" I always like to do one last research sweep to make sure I didn't miss anything AND I DID!!! (yay!) I found a single study that compares all three types of silica when used a foliar spray form 2018! If you search for "The Effects of Foliar Sprays with Different Silicon Compounds" there is a pdf of the paper on semantic scholar from a Dutch researcher. The conclusion is stabilised silicic acid is by far the best form to give plants when used as a foliar spray. This means
1. Colloidal silica does in fact work
2. It's not as good as mono-silicic acid
At least as a foliar spray and that's probably good enough for me.
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