Comparison of Plant Available Silicon (PAS) in several different fertilizer sources.

Silicon has been determined to be a plant beneficial element by the American Association of Plant Food Chemist Organization (AAPFCO) and as such may now be listed on fertilizer labels according to state regulations.

In soils and minerals silicon is abundant but most of it is not in a form that is plant available. In order to compare fertilizer sources for plant available silicon, a new chemical analysis method has been validated. The results from this new 5 day Laboratory analysis may be used on fertilizer labels to guarantee Soluble Silicon content.

Comparison of Plant Available Silicon (PAS) in several different fertilizer sources.
Manufacturer Fertilizer name

(common name)

Total Silicon % Soluble Silicon (Si) %

Plant Available Silicon

JAOAC, Vol. #96, #2, 2013

PQ Corp. AgSil 16H

(potassium silicate powder)

24.6% >8.54%
PQ Corp. AgSil 25 – Sil-MATRIX

(potassium silicate liquid)

9.7% 7.6%
Vanderbilt Minerals VANSIL W10

(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

Fossil Shell Flour

(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 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.
If you have results from another product you would like added to the comparison or if you have a product you would like to see the results from, make a comment or send me an email at custom@customhydronutrients.com

AgSil 16H

AgSil 16H soluble silicon, plant available silicon
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   .
AgSil 16H stock solution (560 grams AgSil 16H in one gallon Ro water)
agsil-stock-concentrate-soluble-silicon-analysis
 Plant Science Concepts, OSA 28
OSA 28 soluble silicon, plant available silicon

Mills Nutrients, Vitalize

Mills Vitalize soluble silicon, plant available silicon

Fertimaster, Power Si

Power Si soluble silicon, plant available silicon

Aptus, Fasilitor (testing paid for by Plant Science Concepts)

Aptus Fasilitor soluble silicon, plant available silicon

Aptus, Fasilitor (testing paid for by third party product customer)

Aptus Fasilitor (2) soluble silicon, plant available silicon

Loveland Products, SST 28

Loveland SSY 28% stabilized silica technology soluble silicon, plant available silicon

PermaGuard, Fossil Shell Flour, freshwater diatomaceous earth

PermaGuard Fossil Shell Flour freshwater diatomaceous earth soluble silicon, plant available silicon