5 ways to give your backyard the best shot at capturing carbon and producing delicious veg

The dirt beneath our feet could hold three times more carbon than our atmosphere, according to soil science and climate experts.

Earth is a huge carbon sink but decades of deforestation, monoculture and poor farming practices are allowing carbon to escape.

However, it’s not all bad news because we now know that by nourishing soil we can improve the quality of plants and animals sustained by it, and help sequester carbon from the atmosphere to help reverse climate change.

Increasing the amount of carbon in the soil by four parts to every thousand would be the equivalent of locking up all man-made greenhouse gas (GHG) emissions, according to Ethical Corporation magazine.

With regenerative agriculture techniques – such as no tilling, crop rotation and tree planting – soil health could be improved, making it a serious player in the race to solve climate change.

Even plants in pots on an apartment balcony can lock up carbon.

Pick a patch, any patch

On a smaller scale, experts say any patch of ground not covered by concrete, tarmac or bricks can store carbon.

That means parks, nature strips, backyards, front yards, verges and other open spaces are potential tools for climate change mitigation. Even plants in pots on an apartment balcony can lock up carbon.

Read What we need to know about soils, including growing things at home on The Fifth Estate

We should all start looking at our backyards and balconies as potential soil carbon storage units.

Not only will growing some plants and produce at home store carbon, it will also help reduce the emissions created by transporting fruit and vegetables, not to mention a whole range of personal wellbeing benefits that come with spending time in nature.

Get to know your soil

It’s a good idea to consider whether lead and other nasties may have contaminated your soil, especially if you’re growing a garden in the city where vehicle exhausts, dust and flakes from lead-based paints may find their way into the soil.

If you’re worried your backyard may be contaminated, or you are just curious to learn what’s in your soil, environmental science researchers working in Macquarie University’s VegeSafe program in Sydney can test it for you.

You can send samples from anywhere around Australia to be analysed for metal and metalloid contaminants for a donation to the program of as low as $20.

Simply fill out a form, follow the sampling instructions and mail your samples and the form to:

VegeSafe
Professor Mark Taylor
Department of Environmental Sciences
Faculty of Science and Engineering
Macquarie University
NSW 2109 Australia

To date, the program has analysed over 13,000 soil samples from 2800 homes around Australia, and the VegeSafe researchers have developed a map showing which areas in Sydney have the highest levels of contamination.

Grow around it

Forty per cent of Sydney samples tested by the program were found to have an excess of 300 mg/kg of lead in garden soils, the Australian guideline for domestic residences. So, if your yard has traces of nasties there are a few things you can do.

The permaculture experts at Victoria’s Very Edible Gardens (VEG) suggest the following:

1. Wash your hands and produce

“Plants are fairly good at keeping lead out of them in normal circumstances,” VEG says. “But if they are covered in soil, or even an invisible layer of dust on fruit or leafy greens, you may be consuming lead from the soil.”

VEG suggests washing your hands and veggies with a splash of vinegar to help dislodge contaminants such as lead.

Read A cheat sheet to composting – the trick is balance!

2. Add organic matter

A good soil should be spongey, crumbly and chocolate-brown, VEG says. Adding organic matter, such as compost, will improve the quality and bind contaminants such as lead, making them less available to plants. But make sure the compost is dry. Wet compost releases methane into the atmosphere.

3. Add high-phosphorus fertiliser and mulch

Phosphate will react with any soluble lead in the soil, making it harder for plants to absorb the contaminant, while mulch will prevent the soil from flying up onto your crops.

4. Avoid root crops, go for fruit crops

Root vegetables are generally the worst affected, so if you grow them and are at all worried about your soil’s quality you must peel them, says VEG.
Leafy greens are also susceptible, especially lettuce, although much of this may be surface borne dust. So, don’t forget to wash the leaves.
The fruiting part is the least affected part of any produce, including all the ‘fruit’ we consider vegetables. Tomatoes, strawberries, pumpkins and any fruit from trees are unlikely to be at risk of lead toxicity, VEG says.

5. Use imported, healthy soil

If you are unsure about what’s in your soil or you have identified contaminated soil, it might be better to start from scratch. Using imported soil in raised garden beds is one way to ensure toxic exposure is minimised.

“Lead is not very mobile in the soil, unless the soil is highly acidic,” says VEG. So, adding new top soil separated by permeable textile fabric will prevent worms and soil organisms slowly mixing the lead through to higher levels.