Comparison of Plant Available Silicon in fertilizer sources.
Soluble silicon in fertilizer sources as determined by the laboratory method detailed in the JAOAC, Vol. #96, #2, 2013
Listed in decending order acording to concentration of soluble silicon. Total silicon also listed for reference.
| Manufacturer |
Fertilizer name (common name) |
Total Silicon % |
Soluble Silicon (Si) % Plant Available Silicon |
|---|---|---|---|
| PQ Corp. |
(potassium silicate powder) |
24.6% | 8.54% |
| PQ Corp. |
(potassium silicate liquid) |
9.7% | 7.6% |
| SioTex Corp. |
Grow-Sil (99.9% SiO2 pure biogenic silica) |
46.7% | 6.28% |
| Vanderbilt Minerals |
(natural Wollastonite) |
24.2% | 3.6% |
| PQ Corp |
AgSil 16H stock solution (560 grams AgSil 16H in one gallon RO water) |
~3.34% | 3.25% |
| Harsco Metals llc |
AgrowSil (calcium/magnesium silicate blend, stainless steel slag by-product) |
12% | 2.2% |
| Harsco Metals llc |
Crossover (calcium/magnesium silicate blend, stainless steel by-product) |
11.3% | 1.9% |
| Plant Science Concepts |
OSA 28 (PEG 400 stabilized silicic acid) |
2.09% | 1.06% |
| Mills Nutrients |
Vitalize (stabilized silicic acid) |
NA | 0.94% |
| Fertimaster |
Power Si (PEG 400 stabilized silicic acid) |
1.71% | 0.88% |
| Aptus |
Fasilitor (PEG 400 stabilized silicic acid) |
1.61% | 0.85% |
| Loveland Products |
SST 28% (stabilized silica technology) |
13% | 0.44% |
| PermaGuard |
(freshwater diatomaceous earth powder) |
~42% | 0.23% |
Total silicon taken directly from the individual fertilizer's label, or calculated from the labeled SiO2 value. Plant available silicon determined by the American Association of Plant Food Control Officials (AAPFCO) approved method.
Silicon Labeling – The format below should be used for guaranteeing Soluble Silicon (Si) in a dry or liquid fertilizer. The method for Soluble Silicon (Si) is in the Journal of AOAC International, Volume 96, Number 2, 2013, pp 251-259. At this time the method is valid for dry fertilizer and will give a slightly lower number for liquids, but liquids should be analyzed by this method until a method is validated for liquids. link to source
This method is detailed by Sebastian et al. in the Journal of AOAC International Vol. 96, No. 2, 2013.
A 5-Day Method for Determination of Soluble Silicon Concentrations in Nonliquid Fertilizer Materials Using a Sodium Carbonate-Ammonium Nitrate Extractant Followed by Visible Spectroscopy with Heteropoly Blue Analysis: Single-Laboratory Validation link to source
The values for the Soluble Silicon in the Harsco Metals, and Vanderbilt Minerals products as well as the PQ Corp AgSil 25 are taken directly from the article in the Journal of AOAC International Vol. 96, No. 2, 2013. All other products Soluble Silicon values have been determined by Thornton Labs at the request of a third party. I will display those analysis results below.
AgSil 16H
AgSil 16H stock solution (560 grams AgSil 16H in one gallon RO water)
SioTex corp. Grow-Sil
Plant Science Concepts, OSA 28
Mills Nutrients, Vitalize
Fertimaster, Power Si
Aptus, Fasilitor (testing paid for by Plant Science Concepts)
Aptus, Fasilitor (testing paid for by third party product customer)
Loveland Products, SST 28
PermaGuard, Fossil Shell Flour, freshwater diatomaceous earth
