Why silica additives are needed in
The silica (SiO2) content in the leaves (etc.) of 'soil grown' plants
ranges from 1-10% of their dry weight. This silica is
potentially supplied from both the feed water and the soil:
Feed water: Natural (i.e.
commonly contain around 5 mg/L soluble silica. Hence soil grown plants
potentially enjoy a
feed of soluble silica each time the plant is watered.
Soil: Sand is composed largely of silica,
roots of soil grown plants are immersed in a potential "silica reservoir".
Although this form of silica is very insoluble it does dissolve
slowly - especially with alkaline waters.
However, plants grown in hydroponic systems
without soluble silica supplements, typically contain much less silica in
their cells. This occurs because, unlike soil grown plants, silica is
virtually absent at the root-zone:
systems: Once the plant
consumes the silica present in the make-up water, no
more silica is available. Of course if either rainwater or RO
(reverse osmosis) water is used, no soluble silica is present.
mediums: Unlike 'soil', inert mediums are unable to yield
Research shows that the
absence of silica in hydroponics can cause plant health to be less than
*Note, silica cannot be included in concentrated
nutrient formulations because stable silica solutions are by nature highly
alkaline. It must therefore be added separately.
When to use Silica?
Silica should be used from seed to harvest: To benefit new growth,
silica must be present at all times in the nutrient solution. Electron
microscopy and x-ray analysis both confirm that once silica is deposited,
it can no longer be redistributed within the plant.