Tuesday, September 10, 2013

Is my soil healthy?

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.


Jess said...

I think that first article is just another example of media scare-mongering. Sure, lead isn't good for you, but nor are the thousands of chemicals that hitch a ride on the fruit and veg we buy from the supermarket.

Anonymous said...

It seems to me that the first article was written by someone with limited understanding of the issue; ie. the author thought contaminated produce was the issue, not the dust attached to it or the dust associated with the soil itself.

Thanks for this post. I was worried about my vege patch in Earlwood, but am no longer due to reading between the lines!

Jason said...

Our concern for our yard is a railroad tie retaining wall and staircase, since those are known to leach a chemical carcinogen into the soil. When I was researching this issue, I found that root crops shouldn't be grown in contaminated soil as the edible part sits in contact with the contaminant. This was fairly easy to avoid. Don't know is something similar is true of the lead you mention.

Jamie said...

HI everyone, Jamie here. Elizabeth O'Brien from the Lead Group, emailed me to say she had problems posting the following email in the comments section here, so I am doing it for her. This is what she wrote about lead in soils

Dear Jamie,

Our charity is perfectly placed to help your readers - with soil lead test kits (where you send the samples in for lab analysis and I write a report with recommendations specific to the results) and with free advice by phone or email (if we get a grant and can continue to run our free info service).

Anyone who does nothing about soil lead contamination in inner city areas before planting a vegie garden or getting poultry is simply underinformed or wrongly informed. My advice: it's fine to spend zero time being anxious or concerned, but please spend your time getting informed and taking action. If you've already been eating your own vegies or eggs from original garden soil, have a blood lead test before you decide whether you have a lead problem or not. If the result is below the limit of detection, you're ok. Take it easy - enjoy your garden.


Yours Sincerely
Elizabeth O'Brien, Founder, The LEAD Group Inc.
PO Box 161 Summer Hill NSW 2130 Australia
Ph +61 2 9716 0014

Emily said...

As an organic gardener I like to think my vegetables are clean and healthy. We had our soil tested a few months after we moved into our new house. I found a lead hot spot in the middle of my new vege patch. I have since converted the hot spot to an ornamental bed. I grow my veges in raised beds and am cautious about using my lawn clippings in the compost which gets added to the vege beds. As a plant scientist the only thing I grow in my soil is fruit trees.

The offer by Macquarie Uni to test your soil for free is a fantastic opportunity to know your own backyard. Regardless of vege gardening, high levels of lead in soil have implications for how your kids play. The recommendation for the soil lead level mentioned in the article is that you minimise contact with soil e.g. by maintaining grass cover.

There is no evidence in Gulson’s research papers that his study participants were consuming home-grown produce so, although his conclusion that diet was a minor contributor to blood lead may have been true for those participants, I don’t see how its relevant here.

Being lead safe isn’t that hard but we need to be aware of the issue. Take a few precautions and maybe your home-grown produce can be as clean and healthy as you hope it is.