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Many fertilisers contain non–food-grade preservatives that most growers don’t even know they’re using.
You might not be eating your fertiliser, but the preservatives inside it absolutely can end up:
So today’s blog uncovers the preservatives you should avoid, why they’re used in the first place, and how to choose safer alternatives.
Any fertiliser or biostimulant containing organic content—seaweed, plant extracts, amino acids, sugars—will grow microbes if left unpreserved, just like a food product would.
So yes, preservatives are necessary.
But there’s a significant difference between:
At Eutrema, we use only food-grade preservatives for two reasons:
Whatever goes into your fertiliser can end up on your produce.
Excessively strong preservatives don’t just kill the “bad guys”—they also kill the beneficial microbes growers want to introduce into their growing media.
Yet many fertiliser companies still use industrial or cosmetic-grade preservatives simply because they are cheap, powerful, and convenient.
Let’s look at the worst offenders.
Carcinogenic. Hazardous. Used in livestock disinfectants.
Shockingly, some fertiliser and seaweed extract products have used it.
I once tested an “organic” seaweed extract preserved with formaldehyde and suffered a severe skin reaction. That manufacturer is now out of business—rightly so.
Avoid completely.
Should never appear in anything that touches consumable crops.
Common example: Benzalkonium chloride
These are found in:
They are:
Any fertiliser containing quats should be avoided outright.
A heavy metal and moderately toxic.
While allowed in some organic systems in very controlled amounts, long-term exposure can cause health issues for both plants and people. Vineyard workers often experience copper toxicity.
It should never be your first choice as a preservative.
Contains bromine and can release formaldehyde.
Also forms nitrosamines—known carcinogens.
Not allowed in food or cosmetics, and should not be in fertilisers.
A powerful sensitiser linked to:
Banned or heavily restricted in cosmetics.
Shouldn’t be anywhere near consumable crops.
Used in some disinfectants and occasionally in plant hormone manipulation (e.g., feminising sprays in cannabis).
But silver interferes with ethylene, the key plant hormone. Misuse can cause:
It is also residual—it doesn’t break down.
Best avoided entirely in fertilisers.
Often, it comes down to poor planning.
A company finalises a formulation, bottles it, and only then discovers:
At that stage, instead of reformulating with safe ingredients, they reach for strong industrial preservatives that can survive high or low pH.
This “afterthought” approach leads to unsafe inputs being added simply for convenience—or cost-cutting.
Because they don’t last.
Great for cleaning a hydroponic system.
Terrible for preserving a bottle of fertiliser for months on a shelf.
Especially sections listing preservatives or additives.
Ask:
“Is this safe to consume or use on food crops?”
This protects:
At Eutrema, products like Gold Leaf / Liquid Gold use only the same types of preservatives you would find in processed foods—not industrial chemicals.
Preservatives are necessary—but not all preservatives belong anywhere near plants grown for consumption. Growers deserve transparency and safer formulation options.
If you have a fertiliser preservative you’d like me to review, send it over—I’ll happily cover it in a future episode or blog post.
Article by Dr Russell Sharp
If you would like to keep up to date with subjects just like this, you can listen to both our podcasts! Links can be found bellow:
Hydroponics Daily Podcast: https://podcasts.apple.com/us/podcast/hydroponics-daily/id1788172771
Cereal Killers Podcast: https://podcasts.apple.com/us/podcast/cereal-killers/id1695783663