Soil testing

Testing Vegetable Garden Soil for Common Contaminants

Testing to determine that your vege’s are growing in contaminant free soil.

About this Testing

Reasons for testing vegetable garden soil

Vegetable garden soil may become contaminated for many reasons. Some gardens were essentially used as rubbish tips in the past and so may have become contaminated by deliberate burial of unwanted waste. Some gardens may have had contaminated soil brought on to the site, while others may have had contaminated water or fertiliser applied. An example of the latter is chicken manure which may contain arsenic due to the addition of Roxarsone (controls coccidial intestinal parasites) into chicken feed.

One of the main reasons for growing your own veges is to make sure you are eating contaminant free food. However if your vege garden soil is contaminated, this may be uptake by the plants and you may be ingesting harmful chemicals.

The following table lists common contaminants, their source and guideline values:


Chemical Class

Biogro Guideline for Soil

(mg/kg dry wt)



Heavy Metal


Arsenic sprays were used to control sheep parasites, but can be found naturally at high levels. Also used as a timber preservative.


Heavy Metal


Contaminant in imported Phosphate rock which is used as a fertiliser.


Heavy Metal


Used as a timber preservative.


Heavy Metal


Used in horticultural sprays and as a timber preservative.


Heavy Metal


High levels in Lead based paints, also used as an anti-knock additive in petrol.


Heavy Metal


Previously used in temperature thermometers.


Heavy Metal



Heavy Metal


Used extensively in industry.


Organochlorine Pesticide


Used to control grass grub and other pests.


Organochlorine Pesticide


Here are some other possible contaminants in vegetable garden soil


Chemical Class



Heavy Metal

Used as a timber preservative.


Organochlorine Pesticide

Previously used in sheep dips.


Organochlorine Pesticide

Insecticide, as well as timber treatment chemical.

Pentachlorophenol (PCP)

Chlorinated Phenol

Previously used as a timber preservative

Benzo[a]pyrene (BaP)

Polycyclic Aromatic Hydrocarbon (PAH)

High levels found in creosote (used for timber treatment), bitumen and tar oil (roading). PAH shouldn’t be a concern for high water content plants such as lettuce, however plants with high oil content may be susceptible to uptake.

Here are the following testing options that we can deliver to someone wishing to test their soils in a vegetable garden:


Compounds in Suite

Heavy Metals + Mercury

As, Cd, Cr, Cu, Ni, Pb, Zn and Hg

Organochlorine Pesticides

Includes DDT, Dieldrin, Lindane etc

Pentachlorophenol (PCP)

PCP and its main metabolite, TCP


Includes benzo[a]pyrene and a number of other PAH

Taking a Sample

Make sure that your sample is representative of the soil in your garden. The best way to achieve this is to take a number of small samples from different places in the garden using a small hand trowel, and put them into a resealable plastic bag. Mix well, remove any weeds and rocks, and send to the lab along with a request form.

In terms of depth, sample the top 75mm (3 inches) of soil unless you are growing root vege’s, in which case sample to  150mm (6 inches).

Sampling equipment:

A small hand trowel and some resealable plastic bags.

Unsure about the correct container to use to submit a sample? Consult our container catalogue


Guides and Supporting Information

Contact Us

Freephone 0508 HILL LAB (44 555 22) or email