The Undies Are In!

By Dr Kieran Meaney

The 2020 Soil Your Undies challenge was a huge success, with over 200 pairs of undies being buried around Australia. In case you missed the excitement last year, the Soil Your Undies Challenge is a collaboration between Dr Oliver Knox, CottonInfo, UNE SMART Farms and UNE Discovery with the goal to increase awareness and understanding of soil health. To do this, participants of the challenge buried a pair of cotton undies for 8 weeks to see how much they broke down. Cotton is made of type of sugar called cellulose which the decomposers living in soil love to eat, so by analysing how much the undies broke down soil scientists like Oliver are able to see how healthy the soil is! Undies were excavated in December and sent back to UNE for analysis, but what exactly do we do with all these soiled undies?

When the undies arrived back at the lab, many of them were still soggy, caked in dirt, and a couple even still had earthworms munching away at them. Don’t worry – this was completely fine. It just meant that the first thing we had to do was to pop all these undies into an oven to dry them out. This helped kill any bacteria still living in the undies, and also helped us to remove the excess dirt. Once the undies were dry, the next step was to photograph them to see how much of each pair was left. We photographed each pair of undies against a black background so that we could analyse the photo and quantify how much of the undies were left. If the undies were still mostly intact however, photographing the undies only showed us the front or back. So to help quantify the breakdown of undies further, they were also weighed so that we could compare them to a fresh set of undies and see how much was missing.

There was an amazing range of undies that came back to us. Some were so degraded only the elastic band and a little bit of stitching were left, while others could have done with a wash and been as good as new! We also got all levels of breakdown in between, from almost intact undies with a few holes, to undies that were a few scraps of cotton loosely clinging onto the stitching. All of these undies provide valuable data about the soil health all over Australia.

In total 78 pairs of undies came back for us to analyse, which means 128 undies are still out there hoping to return home. December is undoubtedly a busy time of year, so if you still have undies that didn’t make it into the post last year it’s still not too late to send them back to us. We’d still love to see them!

Of the 78 undies that did come back to us, there were 19 that had no information to tell us where they were from. While these undies were certainly interesting to look at, without knowing where they came from we unfortunately aren’t able to use this data in the main experiment. In any experiment like this, knowing the location is essential for being able to understand what is happening at different locations or for drawing comparisons and trends between different locations and environments. If you’re still able to send us back a pair of undies, please remember to include at least the name of your school or address and postcode so that we can make the most of every pair of soiled undies.

Most importantly, what did soiling your undies tell YOU about your soil health? Did your undies come out a little more intact than expected? Perhaps your soil might like some compost or a little more water. Was there no cotton left in your undies? What are you going to do to keep your soil health as good as it is?

We’ve certainly learned a lot by running the experiment in 2020, and we are hoping to run the Soil Your Undies challenge again later in 2021. We would love for everyone to keep thinking about their soil health this year, and if you take part in the challenge again you will be able to see how your soil health has changed over the year.