How Safe is your Soil for Self-Sufficient Food Growing : 5 studies included.

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home grown produce

There is an ongoing concern about the safety of soils in the inner cities that may have you wondering about your own patch of ground and if you are at risk if you were to plant into it.

From a self-sufficiency perspective, growing your own food is a great way to begin transitioning from a consumerist lifestyle to a less taxing way of living, so having some information about soil, possible toxicities, remedies, and how you fit into this mix may be valuable for you.

This post will start with a recent news report from 7news in Australia about a recent study by Macquarie University’s VegeSafe program.

Our perspective here at Self-sufficient Homelife is that these reports are very welcome and the media do a job of letting us know about the studies.

The questionable bit is the fear factory settings the media employ to get the story out.

Pb Levels in the Soil.

All soils contain lead. It is a natural element that has uses in the natural world, but that level is not a risk to us at all.

The levels may vary between locations but all-in-all lead (in a natural setting) is no problem. The danger to us in city soils is it is a man-made problem because until 2002 when it was banned, lead was a component or additive to petrol here in Australia.

So it stands to reason that any property that was close to, or down-wind of a major traffic source, would have elevated levels of lead accumulated in the soils.

Then you can add the lead based paints, common for generations, that houses were painted with. When a house was repainted the old flaky paint was either sanded off or scraped off with heat or through sheer hard work.

The old removed paint fell and settled into the soil. But does this make the soil dangerous to grow in?

Here’s a quote from the report referenced in the video above. “high levels of lead were found in more than 35 per cent of the 3600 Australian gardens which had submitted samples.”

There is no mention of where the samples were taken from. They might be from soil near the house under the eaves where you would expect the build-up to be concentrated.

The levels would be concerning if they were taken from actual vegetable garden beds but even then it would not be the end of growing. There are methods of mitigating the problem or designing your way around it as we will discuss further down below.

Lets look at the 7NEWS clip…

Growing Food in the Ground.

In the situation that city folk may find themselves and who only have access to planting in the ground, there is hope for you.

However, it will take some steps for you to limit your exposure to risk. Some understanding of the actual risk vector called for here.

Lead has to be available for plants to take it up through the roots for you to be at risk.

Since most food plants require a neutral or slightly acidic pH level to thrive, this works in your favor because any heavy metal including lead is progressively more bio-available as the soil pH reduces or becomes more acid.

For a large intake by plants to occur, the pH level of the soil needs to move below the plants happy zone, and is likely to harm the plant to the point of early onset of disease and/or insect attack.

The way to check pH is a simple testing kit available at any garden centre, hardware store, or online. Educate yourself to the mechanisms of soil, pH, and periodic elements solubility and plant availability.

Having said all of that, it would be wise to have a layer of mulch that you plant through to protect the plant and you from soil splash.

There are only 2 ways a plant can take in minerals, toxins, and water. Either through the roots or the leaves. pH should protect the roots, and mulch should protect the leaves.

The main point here is check the pH levels first. If in doubt, investigate further.

Are Raised Garden Beds Safe to Grow In?

In the situation of having elevated lead levels in your soil, or even a suspicion of the same, having raised beds will go some way to mitigating the food safety concerns.

But much will depend on how you go about filling them and the quality of the soil in the top 12 inches or 200mm. Just about all vegetables will have their roots in this zone.

The type of bed or what it is constructed of is the next detail to address. Treated pine, or CCA coppers logs should be avoided due to the chemicals used to extend the integrity of the timber against rot and insect attack.

Plants actually love a location where there is plenty of rot and insects because that is the biological soil factory hard at work. The metal kit beds from Birdies are great.

They will stand up to years of use and the amount of compounds they would leach into the soil is almost negligible.

birdies raised garden beds

The main concern with raised beds is where you get the soil from to fill them. In a city you have choices. Garden centers will have access to clean soil.

I would not place too much faith in the quality or growing capacity of the soil. It could be just dirt. Reputable garden centers should look after you.

Can Soil be Made?

Oh Yes. This is a step that is recommended. The process is best described by the video below. This bloke taught me for my Permaculture Design Certificate and knows compost better than anyone.

The science behind this process is sound, proven, and reliable. It can lock up toxins, heavy metals, and other contaminants and tie them to inert substances.

It also unlocks minerals and trace elements and makes them immediately plant available. It is probably the best method for an urban setting. We use chickens to do a similar process but our soil is pretty clean.

If you were to ask my opinion and your soil is questionable, it would be don’t use chickens to make your compost. Learn to make it by hand. Just make sure the heat in the pile gets high. Compost for self-sufficient gardening gives depth to this topic.

compost temperature reading

Reports and Studies.

  • Vegesafe report referenced in the first video. link
  • Map My Environment global soil map with toxicity levels. link
  • Heavy metal pollution of road dust. link
  • Heavy metals and composting benefits. link
  • Effects of biochar for in situ metal immobilization study. link
  • Risk of lead poisoning from urban gardening is low, new study finds. link
  • Lead in Urban Soils: A Real or Perceived Concern for Urban Agriculture? link

In closing, it is a shame that the media lean towards sensationalism to sell the story. At no point should the problem of contaminated soil be taken lightly but news should be just news.

Do your best to cover the ground with lawn to help lessen the chance of kids digging in the dirt. Sandpits are great for this.

Read the reports above, and most of all…..get gardening and become self-sufficient in fresh veggies at least.

Article by Tim Blanch for TheTropicalHomestead.com. He is a qualified Permaculture designer.