Do you fear pollution in your Canberra garden? VegeSafe's soil test might help

The soil in which kitchen gardeners grow their edibles determines the quantity and quality of the crop but how many of us consider whether it contains elements that may be detrimental to health.

A Canberran with a young family who moved into a 1970s house in Scullin heard on ABC TV's Gardening Australia about a soil testing program called VegeSafe.

The program is an initiative of Macquarie University's Department of Environment and Geography and it tests metal concentration of soils using handheld X-ray fluorescence spectrometry (XRF) analysis.

Professor Mark Taylor says VegeSafe was initiated in 2013 to address issues of soil contamination with the increasing popularity in domestic gardening and food cultivation. The principal objective is to inform and educate the community about harmful contaminants that may be present in their garden soil.

VegeSafe also promotes safe and sustainable gardening at home including the growing of vegetables. So far they have carried out 11 tests for home/residential gardeners in the ACT but recent national exposure for VegeSafe has led to 100 samples being received by the team and five per cent of those are from the ACT.

The program operates as a community service and runs on the goodwill of staff and students. Donations to support the program are tax deductible via MQ.edu.au/support. Do register that your donation is specifically for the VegeSafe program.

The Canberra gardener from Scullin sent soil samples from five areas, where he was growing rhubarb, broad beans, raspberries, the bottom corner of the garden and near the house wall. The metal concentrations for arsenic, cadmium, chromium, copper, manganese, nickel, lead and zinc were provided to him with a table of relevant Australian soil standards and international guidelines to use as a comparison.

Taylor and Steven George, who is also in the VegeSafe team at Macquarie University, say all of the eight elements tested for are harmful at certain levels and are the most common found in soils in the domestic environment. Sources include former industrial activity (for example, gas works), pesticide use, lead paint and leaded petrol emissions.

In Scullin, chemical levels were higher near the house and a problem spot was in a small garden bed next to the downhill wall of the house. Consequently, the gardener hasn't planted anything edible within 15 metres of the house.

Having heard about the results, a kitchen gardener with plots at Canberra Organic Growers Society (COGS) garden in O'Connor decided, with permission from other plot holders, to have the soil checked in beds there. Two were from private vegie patches, two from communal garden beds and one from near water tanks beside the church hall.

All the metal levels were safe with "no nasties" and all the lead levels, the heavy metal of most concern to people, were well below the Australian standard for vegie gardens. It was interesting that there was little difference in lead levels between new, imported soil and soil that had been on the inner-suburban site for many decades.

The level of zinc in the tanks enclosure near the eaves came from soil that had been excavated from a metre deep when the hole for the tanks was dug. The gardener who requested the tests pondered whether this was caused by hundreds of galvanised nails that once held down tennis court line-marking tapes as O'Connor COGS was developed on the site of a former tennis court.

When supplying the results, VegeSafe noted that the O'Connor samples were from participant #867, part of an ever growing research cohort of backyard and residential soils numbering more than 4000 across Australia.

Feijoa grafting workshop

On Sunday, August 30, from 1pm-3pm at Canberra City Farm on Dairy Flat Road in Fyshwick, you can learn the skill of grafting feijoas with Mark O'Connor who has led a project, partly developed through readers of the Kitchen Garden column, to find and propagate the best feijoa trees in Canberra.

All participants will be given a grafted feijoa variety of their own choice. $10 members CCF, $30 non-members. Bookings essential: canberracityfarm@gmail.com

Susan Parsons is a Canberra writer.