Your posts triggered my memory about ReXil…
AB Yellow by ReXil, formally SiLife BV, used to be known as OSAB3 under SiLife BV. In ReXil AB Yellow, the PEG-400 functions as a humectant to retain water and prevent polymerization (gelling), stabilizing the orthosilicic acid. And boron is used as an auxiliary stabilizer, again to prevent polymerization of the orthosilicic acid.
When comparing PEG-400 stabilized H4SiO4 to choline chloride stabilized H4SiO4, it has been reported that PEG isn’t as good as choline (“the standard” from the quote below), in terms of orthosilicic acid stabilization. And both are consideraly worse than using carnitine to stabilize H4SiO4, especially with phosphoric acid for acidification and PG (or glycerol, or PG:glycerol) as a humectant auxillary stabilizer (my SOP):
It was observed that polyethylene glycol (PEG-400) does destabilize H4SiO4, where observed gelling time was more than 30% shorter than that for the standard (Table 3 ; Experiment 5 / Experiment 1 ) .
To compare PEG-400 stabizlied H4SiO4 like Power Si or ReXil AB Yellow, make sure you’re providing the same concentation of H4SiO4. Simialry, to compare Power Si to choline stabizlied H4SiO4 like Yara’s ActiSil (not available in the US?), and to carintine stabilized H4SiO4 (my SOP), make sure you’re providing the same concentration of H4SiO4.
From Silicon in Agriculture (an Ebook worth reading; I had a negligible impact on it after conversing with the author years ago):
Today, stabilized silicic acid (SSA) is available in several liquid formulations for foliar application. The first is SSA in comation [sic] with molybdenum and zinc, the second, with molybdenum, zinc, boron, and copper, stabilized with PEG (polyethylene glycol) available as Siliforce® from Agro-Solutions BV (PT). A second series of formulations consists of OSAB3 (SSA also PEG stabilized, combined with boron and other mineral elements), marketed as SAAT (Silicic Acid Agro Technology) by ReXil Agro BV (PT). Both of these companies also supply other products that stimulate plant growth and are synergic whem [sic] applied together with SSA (e.g. L-amino acids). A third is SSA stabilized by Choline rather than PEG and marketed by Yara, ActiSil (poinsettia white paper).
Disclaimer: The leading Partner companies for this blog are: IGNIBRITE INC, USA; REXIL-AGRO BV, ILSA
Regarding testing of Power Si, I just remembered there’s no need. Brian over at Custom Hydro Nutrients already tested it, as well as SST from Loveland. So, it would be better to get ReXil AB Yellow tested to add to the data set. That way, we have test results for all the major stabilized orthosilicic acid suppliers and the newest state of the art that I used to create my SOP:
If you send me some ReXil AB Yellow, I’ll pay for its testing and share the data here. Also, it would make sense to get each product analyzed for plant nutrients (auxiliary stabilizers) as well (B, Mo, Zn, and Fe). So, if you send me some Power Si, ReXil AB Yellow, and Loveland’s SST, I will have their mineral profiles tested and share those data too.
The testing by Brain at CHN shows that Loveland SST has half the orthisilicic acid (PAS; plant avaiable silicon) as Power Si. I’m not sure if the use rate of SST is twice that of Power Si. If not, that shows Power Si is providing a greater concentration of orthosilicic acid. So this could be why you’re seeing more significant results from Power Si.
Also, from reading the LoveLand SST label and SDS, I have doubts it’s PEG-400 stabilized. What’s the pH of the product?
Normally, a mildly acidic fertigation solution won’t affect soil(less) solution pH. Due to chemistry, including what you described from nitrate (OH- release by roots) and use of weak acids. So the impact of low pH on H4SiO4 present in the soil(less) solution would be negligable. That said, your working solution pH is very low, so maybe there’s something to your hypothesis - assuming your use of organic acids isn’t negatively affecting silicon soulblity. Unless you’re already doing so, it would be interesting to take lysimeter samples to spot test soil(less) solution pH, and use the Pour-Thru method for accruate pH measurement.
Lastly, to avoid the necessity of overly low pH, have you considered using polyphosphate? Not the over-priced and over-hyped hydro store product DripClean (with all its sodium). Rather, the AG product from Haifa: GrowClean (N-P-K; with orthophosphate and polyphosphate). I can confirm that GrowClean works very well to achieve your stated goal. And as a bonus, recent research has found that when polyphosphate comprises 10% to 30% of total phosphate, generative plant growth is improved (through various physiochemical effects, including increased Ca and Mg uptake by roots).
P.S. I too use an all nitrate nitrogen supply thanks to the amazing CalPrime. Ammonium can kick rocks, lol. My solutions only have negligible ammonium.