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Dishing the dirt: 8 things you didn’t know about soil

Soil Week Australia Competition

Forget what you thought you knew about dirt – soil is amazing stuff and we should be thinking and talking way more about it

Scratch the surface of most of our biggest challenges in environmental science, climate change and agriculture and you’ll find one thing: soil. Thankfully, it’s finally starting to get the recognition it deserves.

In just the last few years we’ve seen a Netflix feature-length doco on the topic of soil, called Kiss The Ground, narrated by Hollywood star Woody Harrelson, and closer to home Aussie celebrity chef and farmer, Matthew Evans published a book called Soil in 2021.

So why all the fuss? Well, as Matthew Evans – better known for his SBS TV series, The Gourmet Farmer – puts it: “Because with no soil, there’s no us. Healthy, living soil is vital for healthy humans.”

You probably already have a pretty good sense that healthy soil is important for growing stuff like, you know, the food we all need to stay alive. But there’s a lot more to soil than that – here are eight earth-shattering soil facts to get you started:

1. Soil is the most biodiverse ecosystem on the planet

Yep, it’s crowded with life down there! You might have thought the Great Barrier Reef was a diverse ecosystem, but if you could go soil snorkelling, you’d be amazed at what you could see: Just one teaspoon of topsoil can contain up to 10 billion microorganisms – think bacteria, fungi, insects and earthworms.That’s more than the population of humans on Earth … in a teaspoon!

2. Soil isn’t as solid as you think

In fact, about 25% of healthy soil is air – and it breathes, constantly exchanging gases with the atmosphere. The rate of this breathing, or respiration, is in fact one indicator of the microbial activity in soil, and therefore the health of the soil.

3. Soil can help us fight climate change

Plants use a process called photosynthesis to grow, turning sunlight, water and carbon dioxide into energy. As a result, plants contain carbon that they’ve pulled out of the atmosphere. As soil is made up of broken down plant matter, it is therefore considered an important ‘carbon sink’ – which means it can naturally absorb more carbon than it releases, helping us in our fight against climate change.

Unfortunately, poor land management and farming practices disturb the topsoil and release much of this carbon back into the atmosphere – where it contributes to the man-made emissions that are warming the planet.

Luckily, clever scientists and farmers are cottoning on to this and looking at ways to maximise soil’s important role in locking up carbon. Advocates of new approaches such as regenerative farming, which focuses on building topsoil (rather than letting it literally blow away!) argue doing so has the added benefit of improving the quality and amount of food produced. So it’s a win-win for the climate, and our plates!

4. Soil can help farmers survive drought

Locking up carbon in soil has another benefit – 1% increase in soil organic carbon increases the capacity of soil to hold water by about 2%. This can equate to hundreds of thousands of litres per hectare, and make a big difference to farmers’ yields and their ability to survive during extreme drought.

5. Soil can make it rain!

Speaking of weather and climate – did you know there is growing evidence that microbes can fly up from Earth and actually cause rainfall? This is called ‘bio-precipitation’. As Matthew Evans says: “Maybe a rain dance isn’t a dumb idea after all?”

6. Topsoil is super thin

‘Topsoil’ is what we call the outermost layer of soil, it’s where most of those 6-billion-per-teaspoon organisms hang out, and it’s where we grow 95% of our food. So topsoil is a very big deal – but it’s also disconcertingly thin on the ground: about 25cm deep to be precise. Imagine if it took a year to get from the surface to the centre of the Earth – you’d spend less than a second in the topsoil!

7. Soil is disappearing!

Just as you were starting to get a sense of how incredible this stuff is, we have some bad news: we’re losing our soil at an alarming rate. The ‘half-life’ of some topsoils (in other words, how long it takes to lose half of it) is measured in decades, thanks to practices such as logging and approaches to farming that disturb the structure of the soil and let it blow away – contributing to climate change, rather than playing a role in preventing it.

8. Humans are way faster at making soil than nature

Unfortunately, as you’ve just read, with current farming practices, we’re doing a pretty good job of eroding and degrading our soil. And if we had to leave it up to nature to fix our mistakes, we’d be in a pickle: it can take up to 1000 years to form 1cm of topsoil! Thankfully, humans can also make our own soil (hello compost) and restore degraded soil through better land management and farming practices. There are already farmers doing this and surviving drought while looking after the soil. 

9. You could win amazing prizes just talking about soil

Huh, we snuck that one in there, didn’t we? But seriously – if you read this far and are in years 7 to 10 in an Australian secondary school, it’s time to get creative. Soil Week Australia has launched a schools competition with the theme ‘Healthy Soil’. To enter, create a project that explores healthy soil and its role in agriculture and climate in any digital format – think essay, video, artwork, app. Be creative! The winning entrant will win a $500 JB Hi-Fi voucher for themself, and $1000 for their school. 

Another competition category is available for primary school students in years 4-6.

Find out more at

This post was brought to you in partnership with Soil Week Australia, an initiative of Healthy Soils.


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