Tuesday, September 10, 2013
There was such an interesting letter in the Sydney Morning Herald this morning that I thought all vegetable growers who missed it might want to know what was said.
To set the scene briefly, last Saturday the Sydney Morning Herald ran a story entitled "Lead threat to children from home vegies", accompanied by a photo of backyard soil testing. The gist of the story was worrying, and probably confirmed the worries of many people, especially those in older inner-city areas. What's in the soil? Is there lead? Other dodgy chemicals from days gone by which still have a thousand years to go before they break down? Here's that story (click on the image and it should come up bigger if you are not reading this post via your email).
Then, this Tuesday morning, a letter from Emeritus Professor Brian Gulson of Macquarie University appeared, suggesting a less worrying interpretation of the "lead in soils" issue. Here's the professor's letter.
Hopefully you can read the professor's letter, but the gist of it is that lead in soils doesn't transfer easily into vegetables grown in those soils. He does mention that lead in the air can deposit on leafy vegies such as lettuce and spinach, but that good washing before cooking should remove that lead. He also goes on to conclude that "garden produce is not the problem" (with lead in children).
Living in an area on the edge of the inner-cty, I've always been interested in the health of my soil, and from simple historical research I know that my local area was farmland before it was turned into housing land. It was never industrial land. Readers of this blog in inner-city areas might have a different history of land use for their plot of ground.
While the professor's letter offers some research-based evidence, I do have a couple of thoughts on this issue that I would like to share.
1. If you are worried about your soil's health, the professor's letter provides some evidence for a calmer approach.
2. If you have a gut feeling that your soil isn't trustworthy, then you have two good, clear choices. Either (a) grow your produce in large pots of potting mix, or (b) grow your produce in raised garden beds. A raised bed 30cm high is adequate for most vegies.
3. I did have a conversation with a soil scientist a while back about this issue, and he did mention that leafy vegies such as silver beet, spinach, Asian greens and lettuce do "suck up" minerals and nutrients from the soil at a much faster rate that fruiting veg (tomatoes, chillies, capsicums) or root veg (potatoes, carrots, beetroot).
So, if my soil scientist is right, perhaps you could grow your fruiting vegies and root vegies in your soil, and your leafy greens in pots or raised beds?
FInally, I'm very conscious of the fact that most of the "contaminants" in my organic urban garden come here via the air, from car and truck exhausts, planes zooming overhead, and polluted city air in general. The main thing to do in this case is thoroughly wash everything you grow at home before eating it.
I hope some of this helps, but I do think that the scare stories the Herald and other newspapers regularly run on all sorts of health issues cause more anxiety – a major modern health problem – and are in themselves a health hazard.
Posted by Jamie at 8:12 AM