AgSil Potassium Silicate and Fertilizer Injector Concentrates

Why Silicon Matters for Plant Health

Silicon is recognized as a beneficial element for plants. AgSil potassium silicates — including AgSil 25, Pro Powders Silica Pro, and AgSil 16h — deliver plant-available silicon that supports:

Resistance to mineral stress
Reduced climate stress
Improved plant strength and structure
Increased growth and yield

Soluble silicon must be constantly maintained at low concentrations in the root zone for effective uptake. Plant uptake and incorporation of silicon is necessary for the full benefits to be realized — after root uptake, silicon moves through the plant via the transpiration stream. Foliar applications may provide direct bio-stimulant effects and some activity against pests and pathogens, but do not deliver the same systemic fortification as root-zone silicon. Source: Silicon in Agriculture; From Theory to Practice

For questions about choosing the right silicon source for your hydroponic or fertigation program, see Dr. Daniel Fernandez’s excellent post: Common questions about silicon in nutrient solutions at scienceinhydroponics.com.

Potassium Silicate Products Available from Custom Hydro

Three proven potassium silicate options are available now:

Pro Powders Silica Pro — Dry potassium silicate powder; closest direct replacement for AgSil 16h. Use at 0.25 g/gallon for continuous feeding programs.
AgSil 25 — Liquid potassium silicate (21% SiO2, 8% K2O); ideal for fertigation and automated injection systems. Use at 0.47 mL/gallon.
AgSil 16h — Dry potassium silicate powder; currently on backorder until late June 2026. See our replacement guide.

Preparing Stable Concentrated Stock Solutions

In hydroponics and soilless greenhouse media, growers should supply a constant low level of soluble silicon in the fertigation feed. Fertilizer injectors (Dosatron, Dosamatic, Argus, Anderson, Netafim, etc.) are ideal for this — but concentrated potassium silicate stock solutions require special preparation to remain stable.

Concentrated potassium silicate solutions are not stable at environmental pH. Without proper preparation, stock solutions will become cloudy, precipitate, or gel (polymerize). Follow these steps to prepare a stable concentrate:

Start with a half-full stock tank of distilled or deionized water
Before adding potassium silicate, raise the pH of the starting solution above 11.3 using potassium hydroxide (approximately 0.3 g KOH per liter)
Add the required amount of potassium silicate to reach your target silicon concentration
Top off with additional deionized water that has also been raised to pH >11.3
Keep the stock solution covered to prevent CO₂ absorption, which lowers pH and causes cloudiness and instability

Source: Fatzinger & Bugbee (2021) — “pH 11.3 Enhances the Solubility of Potassium Silicate for Liquid Fertilizer”, Utah State University Digital Commons.

Injector Setup and Mixing Order

When incorporating silicon into fertigation or hydroponic systems, mixing order is critical:

Silicon first — Always dilute potassium silicate into the working strength solution before adding any other fertilizer inputs
Dedicated injector — The silicon injector must be the first in the series; never share a header with other concentrated fertilizer solutions
Mixing chamber — Always include a mixing chamber after the silicon injector to ensure complete dilution before other inputs are introduced
Venturi/A-B systems — Silicon cannot be injected into common A-B headers. Add a separate auxiliary injector channel dedicated to silicon
Keep concentrates separate — Concentrated potassium silicate must never be combined with other concentrated fertilizer solutions to prevent precipitation, cloudiness, and polymerization