Soil bought from a garden centre

What is really in the garden soil when ordered from a garden centre. I have found plastics, aluminium shards etc This a veggie mix from a reputable garden centre, all 1 1/2 tons of it.


Really depends on the source.

Generally garden soils from garden centres contains organic and inorganic (mineral) components. Some also contain fertilisers, gypsum, wetting agents or other soil conditioners.

The organic component is usually compost made from the decomposition of some vegetative sources. This can include farm residues (e.g. manures, sawdust/wood shavings from chicken sheds, stable flooring, low quality produce and other farm wastes), vegetation wastes (green waste generated from the pruning or removal of vegetation), food processing wastes (such as bagasse, fruit and vegetable residues, husks of seeds etc), biosolids from waste water treatment plans (municipal sewage collection, abattoirs or food processing facilities), municipal wastes such as wasted food and other organic materials disposed in the waste stream and sometimes industrial wastes (such as paper manufacture wastes).

The mineral component can be ashes from boilers (power station or industrial), extractive industry residues (such as cracker/crusher dust or materials that don’t meet the required product specification, sandy loams etc), natural soil (this is becoming less likely as soil is a finite resource), vermiculite (for light weight mixes) and other inert materials which are suitable for use (such as crushed concrete dust, overburden/spoil from earthworks etc).

If a soil mix contains plastic, it means that it has been contaminated with the materials as a result of the primary ingredients used to make the soil mix. Without seeing the soil, I would suggest that the plastic is from bags or other pastic materials which often are found in green waste. Such is very hard to remove and will remain in the soil mix. Soil screening will remove larger particles, but smaller particles will still get through the sieves.

This is possibly a lesson to learn, as most soil mixes bought at garden centres are made from recovered materials (as outlined above), if one throws the wrong thing in it will contaminate the end products.

The plastic and aluminium is inert and shouldn’t affect the quality of the soil mix. It is more a cosmetic issue than a plant growth issue. Having plastic is a soil also means that it will always be there as it won’t break down.

I would let your soil supplier know the the contamination as it is something they should be made aware of (if they don’t already know).

There is also an Australian Standard AS4419 and AS4454 which provide basic testing regime for garden soils (AS4419) and composts (AS4454). Both outline the acceptable level of contaminates which can be present

Also, if you have any further questions, you are more than welcome to ask. The manufacture of soils and resource recovery is an area of interest and one I provide lectures on.


Good reply.However, compliance to the (horticultural) Standards (including the potting mix AS 3743 standard) is not compulsory since they are not regarded as seriously health issues (such as motor bike or bicycle helmets).
So what it boils down to is the product you purchased “certified” (by an organisation independent from the manufacturer) for compliance to the relevant Standard? - in which case there should be some evidence of such (e.g. the ‘5 ticks’ logo on bagged composts, soils & potting mixes) or a clear statement of certification on the paperwork for bulk products.

It should mean the “certified” product is better quality, but it may also mean you have to pay more, since the Standards certification process can be costly.

By the way, a statement that the product is “compliant” doesn’t necessarily mean it is “certified”.



And the other thing to note is that certification under Australian Standards for ‘soils for landscaping and garden use’ and ‘composts, soils conditioners and mulches’ is voluntary. If it shows the ticks it means it is certified.


thank you for your information. It is quite worrying to be finding plastics of various types from soil meant for fruit and vegetable from a major supplier after 5 years. Sometimes there is even broken glass.

Most likely one of the components of the mix that you have comes from garbage re-cycling. Material from waste depots is shredded and composted and then sold in bulk, as compost. I would think the supplier buys this in large quantities. Only organic matter is supposed to go through this but as you have found sometimes the operators at the tip are not too careful and all kinds of material goes in. So you see bits of plastic, metal and glass that have all been shredded but of course they don’t compost very well!

Since it has already been delivered there is little you can do about it unless you want to try for a refund or partial refund on the grounds that the product is not suitable for the purpose.

For all who are thinking of buying this kind of product before you buy examine the heap where your compost will come from very carefully before you pay. If you cannot examine the product before buying then buy elsewhere.

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My wife is a horticulturist and she usually gets me to do the large shovelling and barrowing jobs (tons if it!), and there is certainly a lot of plastics in the soil, usually blue, so perhaps old pots that have been through a mulcher, and there are also the remains of thin plastic garbage bags. This is all due to people putting non-organic rubbish in with the vegetable matter, which the council says not to do at the recycling centre.

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