I've spoken to a lot of growers over the years — backyard gardeners, market gardeners, broadacre farmers — and when things aren't going right with their plants, the conversation almost always starts and ends with nitrogen, phosphorus and potassium. Which makes sense. NPK is what's on the bag. It's what's taught. It's what gets measured.
But there's another element that doesn't get nearly enough attention, and in my experience it's often the missing piece. Silicon — or more specifically, plant-available silica — is quietly doing some of the most important work in a healthy garden, and most Australian soils are running low on it.
What silica actually does inside a plant
When a plant takes up silicon, it deposits it into its cell walls. That sounds simple enough, but the effects ripple out in ways that aren't immediately obvious.
Physically, the plant gets stronger. Stems hold their structure better. Leaves resist being chewed through. Roots push deeper. The plant stands up to heat and wind in a way that soft, silicon-deficient growth just doesn't.
There's also a disease resistance angle that I find really interesting. Silicon creates a physical barrier in the leaf surface that fungal spores genuinely struggle to get through. We've had growers reduce their fungicide programs significantly after incorporating silica — not because we told them to, but because they stopped needing to spray as often.
And then there's water efficiency. Silicon reduces transpiration loss through the leaf surface, which means plants cope better in dry spells without as much irrigation. For Australian conditions, that's not a small thing.
Why our soils tend to be short of it
Australia's soils are some of the oldest and most weathered on the planet. Millions of years of leaching have stripped out a lot of what was once there, including plant-available silicon. Heavy irrigation speeds that process up. And most conventional fertiliser programs don't bother replacing silicon at all — so the deficit compounds over time.
The result is plants that look okay on the surface but are running at a fraction of their potential. Softer growth. More fungal issues. Higher pest pressure. More reliance on sprays that treat the symptom rather than the underlying problem.
How to tell if your plants are silica-deficient
There's no single dead giveaway, but a few things together usually tell the story:
- Stems that flop or need staking when they shouldn't
- Recurring powdery mildew, black spot or botrytis no matter what you spray
- Insect damage that keeps coming back season after season
- Fruit with poor skin quality, or that splits in warm weather
- Lawn that stays soft and thatchy rather than building a firm, dense sward
If you're ticking two or three of those boxes, silica is worth looking at before you reach for anything else.
What we'd suggest
SilicaMax is our liquid silicon concentrate, and it's what most of our customers start with. It's straightforward to apply — either as a foliar spray or through your irrigation — and because it's in a plant-available form, you tend to see results within four to six weeks. Firmer structure, stronger colour, and usually a noticeable drop in pest and disease pressure.
For lawns, two applications a year — early spring and again in autumn — is enough to build real soil biology and turf density over time.
If you're running a spray program on a larger scale, UltraSilica Wettable is the powder format that mixes easily into existing tank mixes. Same results, more practical for broadacre.
Give it a season. The plants will show you whether it's working.
BioCare Agronomy Team
BioCare Fertilisers · Healthy Earth