Do you have a backyard veggie patch? How safe is your soil?

Earlier this year we planted a demonstration and teaching garden out the front of The Joinery, home of the Adelaide Sustainability Centre. Our garden is a mixture of edible native plants, perennial edible vegetables, herbs, edible flowers and plants native to the Adelaide plains to provide habitat for our local wildlife.

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The Joinery, 111 Franklin Street, Adelaide. Photo by Mathew Turner

Given that our garden is on a main road in the middle of the CBD, on a site that was once the old central bus station, we wondered if the produce from our garden would be safe to eat.  Could there be unhealthy levels of metals and metalloids in the soil? These may have built up over time as a result of pollution from manufacturing, traffic, building renovations or past uses of the property. To find out, we sent soil samples off for testing with VegeSafe.

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Vegetable Garden and nearby bus parking. Photo by Diane Salvi

VegeSafe is a free soil metal testing service offered by Macquarie University’s Environmental Sciences staff. This program is available for people from any Australian state or territory. Using ‘XRF’ (handheld X-ray fluorescent analyzer) to screen for metal concentrations in your soils, VegeSafe test for metal and metalloid contaminants that are most likely to cause a risk to human health when elevated in very high concentrations in backyard soils. These are arsenic, cadmium, chromium, copper, manganese, nickel, lead and zinc.  A formal report is sent to you by email, along with links to further information if contamination is an issue.

It’s an easy process to get your soil tested. Simply follow the instructions provided regarding how to take your 5 soil samples, seal them in bags, label them, sign your consent form and post this to VegeSafe. We collected and mailed our samples on 18 November 2016 and received a report on 13 December 2016, it cost us $13.80 to mail 1.42kg of soil (in a pre-paid Australia Post 3kg mail satchel).  If you are worried about soil contamination in your backyard  or plan to setup a roadside verge garden we recommend testing your soil with VegeSafe.

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Soil testing. Photos by Diane Salvi

Our Results

See below for the full report received from VegeSafe.  To summarise, any metals found in the soil at The Joinery were found to be present in levels below the thresholds listed in the national guidelines for soil in the Residential A category (for garden/accessible soil – home grown produce <10% fruit and vegetable intake, no poultry – also includes childcare centres, preschools and primary schools.) We can safely eat the produce from our garden.

Metal Concentration Results for Soil at The Joinery

Dear VegeSafe Particpant (The Joinery): Below are the total metal concentrations results from the X-ray fluorescence analysis of your soils. The analysis of your soil is subject to various limitations including moisture content of the soil, its grain size and organic content. In a standard laboratory test additional and more intensive preparation of your soil samples would occur allowing greater reliability of the results. Therefore, we advise you that the analyses provided below are subject to these technical limitations and should be taken as a guide to the metal content of your soil. If you require more detailed analyses we recommend that you submit your samples to a laboratory accredited by NATA, which is the National Association of Testing Authorities – http://www.nata.asn.au/facilities-and-labs. We have made a short guide of how to deal with soil that may be contaminated with elevated lead or other metals – this can be found at the following website: http://research.science.mq.edu.au/vegesafe/advice-on-soil/

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Australian and International Guidelines for Urban Soil in Residential Areas

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A complete version of these guidelines including URL links is available here.

Residential A = with garden/accessible soil; Residential B = with minimal access to soil; Recreational C = public open space

Thank you to the Adelaide and Mount Lofty Ranges Natural Resources Management Board for funding the development of our garden.

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