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Why did 1,000 Swiss citizens bury their underpants?
Study: Land use is the biggest factor in determining decomposition rates of organic cotton underpants.
One thousand Swiss citizens voluntarily buried their cotton underpants for two months—not to keep the Underpants Gnomes from stealing them, but as part of a citizen science project to map out soil health across Switzerland. The results of this unique experiment were reported in a new paper published in the journal Plants People Planet.
“Our results show that how soil is managed can significantly affect both soil life and soil quality,” said co-author Marcel van der Heijden, an agroecologist at the University of Zurich. “Healthy, biologically active soil is crucial for fertility, nutrient cycling and many other ecosystem services.”
Soil health is critical for agriculture and, by extension, food security, not to mention a healthy global ecosystem, but it has been declining worldwide, per the authors. One key indicator of soil health is decomposition rates of complex organic matter, breaking down stuff like leaves, wood, even cadavers into simpler organic and inorganic compounds, releasing C02 and nutrients in the process. There have been relatively few large-scale national decomposition studies involving different land use types, although smaller studies have shown that how humans use a site can significantly affect the soil’s biological diversity.
Commercially available teabags are a common material used to measure decomposition rates, known as the “teabag index” (TBI). However, Van der Heijden and colleagues felt the teabag index could be improved upon, given that it requires careful handling and specific tools, like a fine scale balance. They opted for a more playful approach to illustrate soil composition.
Prior research had shown that cotton strips could also be used to assess decomposition, so why not engage in a bit of citizen science and ask volunteers to bury cotton underpants for a couple of months, then dig them up and record the results? That’s exactly what the authors did in a national project they dubbed “Proof by Underpants.”
Van der Heijden et al. recruited 1,000 Swiss citizens across the country—240 of whom are listed as co-authors on the paper—and sent them an activity pack: two pairs of organic cotton men’s underpants, 12 teabags, and a sampling bag for soil collection, along with detailed instructions. Each volunteer selected a site, dug a hole, and collected a soil sample. Then they inserted the two pairs of underpants vertically, side by side, with the synthetic waistband visible on the surface.
They also placed six teabags in front of each of the garments to compare how the underpants performed vs. the TBI in terms of decomposition assessment, and then refilled the hole. Participants dug up the first pair of underpants and associated tea bags after 30 days and the second after 60 days, documenting the condition of the items and mailing all the materials to the scientists for analysis.
The results: Land use was the most important factor. Underpants decomposed the fastest in private gardens, where soil analysis also revealed the highest levels of organic matter, making it an ideal environment for earthworms, fungi, bacteria, and so forth. Lawns showed the least activity of soil organisms, with agricultural fields and meadows ranging in the middle. Temperature and moisture levels also affected organism activity, particularly if conditions were too cold or too dry, as did soil nutrient levels.
Overall, the authors found that their “underpants index” provided equally meaningful information about soil conditions as the TBI, including chemical and physical properties, elevation, and moisture. And unlike TBI, the underpants “provide a direct visual and haptic measure of decomposition that is easier to interpret,” they wrote. This makes it “an ideal tool to be used in citizen science projects and to raise awareness for soil-related issues.”