Potassium Silicate

Potassium Silicate

Potassium Silicate is a water soluble silica and potassium powder, 53.00% SiO₂ (24.8% silicon) and 32.00% K₂O (26.6% potassium). It suits growers who want to add plant available silicon to irrigation water or foliar sprays, raise the pH of their water, or emulsify neem oil for pest sprays.

At a glance

• Type: soluble mineral salt (silicon and potassium)
• Organic input status: not certified; a manufactured input. See the note on its organic status.
• Analysis: NPK = 0 - 0 - 32 (N, P₂O₅, K₂O); silica 53.00% (24.8% Si); potassium 26.6% elemental
• Use for: soluble silicon in irrigation or foliar sprays; raising water pH; emulsifying neem oil
• Rate: make a concentrate of 148 g per litre of water, then use half a teaspoon of concentrate per 10 litres as a foliar spray

What it is

Potassium silicate is one of the few forms of silica that dissolves in water, which is what makes it useful for irrigation and foliar use. Many liquid silica products are potassium silicate dissolved in water; our Liquid Potassium Silicate is this powder at 148 g per litre. It is not the same as insoluble silica powders such as diatomaceous earth or rock dust, which release silicon slowly if at all.

What it does

• Supplies silicon in the soluble form plants take up. Silicon is laid down in cell walls and stems, hardening them, and growers use it for sturdier plants and some resistance to mildew and stress. Build it in early.
• Supplies potassium, 26.6% as the element.
• The solution is strongly alkaline, so it is the usual way to raise the pH of irrigation water or a nutrient solution.
• Works as an emulsifier: it lets neem oil mix into water for pest management sprays.

Analysis

NPK = 0 - 0 - 32 (N, P₂O₅, K₂O); elemental potassium 26.6%

• Silica (SiO₂) 53.00% (24.8% Si, elemental)
• Potassium (K₂O) 32.00% (26.6% K, elemental)

How to use

• Concentrate: dissolve 148 g in 1 litre of water to make a 7.8% liquid solution (7.8% SiO₂ w/v) that you can store and dose from.
• Foliar spray: half a teaspoon of concentrate per 10 litres of water.
• Neem oil emulsifier: add 3 g of potassium silicate to 30 ml of neem oil, then mix into 10 litres of water to make the final spray. Spray once a week over all plant surfaces until it runs off.
• Soil drench: use the same concentrate, diluted, through irrigation; see the Liquid Potassium Silicate page for the soil rate (2.5 to 5 ml of liquid per 10 litres).

Learn more in fifteen seconds

• Silicon: what it does
• Soil pH, water pH: how to move it

Handling and storage

• Wear a mask to avoid inhaling particles and open in a well ventilated area.
• Wear gloves and eye protection, and wash hands after use.
• Once opened, keep sealed and dry.
• Potassium silicate is strongly alkaline. Wear gloves and eye protection when making the concentrate, add the powder to the water and not the other way round, and check the pH of the final spray or feed before it goes on; a strong solution will burn leaves and push a soil or nutrient solution well above target. Do not mix it concentrated with acids or with calcium or magnesium salts, which precipitate it out. Test a few leaves first.