A buried pair of cotton briefs ranked 1,000 Swiss soils by biological activity
Volunteers buried more than 2,000 pairs at about 1,000 Swiss sites and dug them up two months later, and land use predicted how much fabric vanished better than most of the soil chemistry measured. That makes cotton a usable, if coarse, field assay.
The Scientist · Science desk
What happened
- Researchers at the University of Zurich and Agroscope launched the citizen science project Proof by Underpants in 2021 to gather data on soil life, an ecosystem the team says is easy to overlook.
- Following one standardized procedure, 1,000 volunteers buried more than 2,000 pairs of cotton underwear and 12,000 tea bags at around 1,000 locations across Switzerland.
- Cotton disappeared fastest in private gardens, which held the highest levels of organic matter, while lawns showed the least active soil organisms and agricultural fields and meadows fell in between.
- Land use turned out to be the strongest predictor of decomposition rate, explaining the differences between sites better than most of the soil properties the laboratory measured.
- Around 240 citizen scientists are listed as co-authors of the publication, which the researchers describe as a reflection of exceptionally high participation.
Why it matters
- What's now possible capability A standardized cellulose strip converts untrained hands into a comparable measuring network, which is how a national map of soil activity got assembled from all regions of one country at once.
- What it limits constraint Since identical fabric loss can come from warm damp ground or from unusually busy organisms, one buried garment cannot separate management from weather, so any local reading needs a paired plot buried the same week.
- What doesn't add up contradiction The project leaders' own caveat works against the index's simplicity: fast loss reads as good news in a production field and as a warning sign in a forest, so the score carries no consistent direction.
- What it sets up precedent Putting the volunteers in the author list rather than the acknowledgements raises the bar for what large citizen science projects are expected to give back to the people who collect the samples.
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Cotton is mostly cellulose, and that is the whole trick: bury it, and anything in the soil equipped to break down a polysaccharide begins eating, so the fabric that goes missing stands in for how busy the organisms are [17]. What comes back from the lab is mass lost over a fixed window, photographed on retrieval and posted in with a soil sample [2]. That figure is a sum, not a measurement of one process. It cannot say whether earthworms or fungi or bacteria did the work, and it does not separate biology from weather. The team is explicit about the second part: soil activity tracks temperature and moisture, and soil that is too cold or too dry is barely active at all [7].
Repetition is what rescues a crude assay. About two pairs per location [20] tells you very little about any single garden. A thousand locations, all following the same protocol, is enough to sort land uses by decomposition rate [4].
The design is observational. Nobody assigned gardens and lawns to sites at random; the people who keep gardens also compost, irrigate and plant differently. So the reported result is that a site's land use category explains more of the variation in fabric loss than most measured soil properties do, with nutrient chemistry also contributing [5][6]. Co-study leader Marcel van der Heijden, a UZH professor of agroecology, reads that as management affecting both soil life and soil quality [9], and the team's suggested levers are permanent soil cover, compost, diversified rotations and restraint with mineral fertiliser and pesticide [10]. Those levers were not tested one at a time in this study. They are the plausible mechanism behind a ranking, which is a different kind of evidence.
Then there is the direction problem, which the researchers raise themselves. Franz Bender of Agroscope, who co-led the project, says maximum decomposition is not desirable in every ecosystem: in near-natural habitats such as forests, very high nutrient levels can indicate a disturbed nutrient balance, and in gardens fast decomposition may signal oversupply [8]. Underwear that has nearly vanished is not automatic evidence of a balanced system [16]. A high score has to be read against what the site is for.
One gap is worth naming. Volunteers also buried 12,000 tea bags, roughly a dozen per location [21], and neither the announcement nor the coverage of the paper in Plants, People, Planet [3] describes what the tea bags showed [23]. A second substrate with different chemistry is the obvious internal check on the cotton signal, and it is the part of this dataset I would wait for.
If you want to run the proposed underwear index on ground you manage [19], the useful form is a contrast rather than a score: same burial date, same depth, two plots differing in one thing you control. The Swiss project's contribution is standardisation at a scale that would have been difficult and expensive to buy [15], producing what the university calls one of the country's most comprehensive soil-life datasets [14]. Participants got individual soil results, evaluation tools and management advice back [12], which is also how you keep a thousand people burying things on schedule.
What to watch
- Publication of the tea bag results, which would let the cotton signal be checked against a second substrate with different chemistry.
- A repeat burial at the same Swiss sites in a different season, which would size how much of the ranking is weather rather than management.
- Any attempt to calibrate the proposed underwear index against direct measures of soil organism activity rather than against land use labels.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence55
- Adoption
- Not scored
- Hype gap+15
- Incentives30
- Confidence60
Perspective Coverage
3 publishers- Builder
- Builder 28%
- Operator
- Operator 62%
- Investor
- Investor 10%
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Following a standardized procedure, 1,000 volunteers buried more than 2,000 pairs of cotton underwear and 12,000 tea bags at around 1,000 locations across Switzerland.
- [2]
Two months later the volunteers dug up the buried items, photographed them and sent them to the laboratory together with a soil sample for further analysis.
- [3]
The results were published in the journal Plants, People, Planet.
- [4]
The underwear decomposed most rapidly in private gardens, where researchers found the highest levels of organic matter; soil organisms were least active in lawns, while agricultural fields and meadows fell somewhere in between.
- [5]
Land use proved to be the most important factor influencing how quickly the underwear decomposed, and whether a site was a garden, meadow, cultivated field or lawn explained the differences better than most of the soil properties measured.
- [6]
Chemical soil characteristics, such as nutrient levels, also played a significant role in decomposition rate.
- [7]
Soil life depends strongly on temperature and soil moisture; if conditions are too cold or too dry, the soil is barely active.
- [8]
Franz Bender, co-project leader and head of the agroecological assessments team at Agroscope, said maximum decomposition is not desirable in every ecosystem: in near-natural habitats such as forests, very high nutrient levels can indicate disruptions to the natural balance of nutrients, and in gardens rapid decomposition may point to an oversupply of nutrients.
- [9]
Co-study leader Marcel van der Heijden, UZH professor of agroecology, said the results show that how soil is managed can significantly affect both soil life and soil quality, and that healthy, biologically active soil is crucial for fertility, nutrient cycling and many other ecosystem services.
- [10]
Measures that can promote soil life include keeping the soil permanently covered, adding compost, diversifying crop rotations and limiting the use of mineral fertilizers and pesticides.
- [11]
The exceptionally high level of participation is reflected in the authorship: around 240 citizen scientists are listed as co-authors of the publication.
- [12]
The researchers provided participants with individual feedback, including soil analysis results, evaluation tools and tips for sustainable soil management.
- [13]
In 2021, researchers from the University of Zurich (UZH) and Agroscope, the Swiss federal centre of excellence for agricultural research, launched the citizen science project Proof by Underpants (Beweisstueck Unterhose) to draw attention to soil as an overlooked ecosystem and to collect scientific data.
- [14]
The data come from all regions of Switzerland and form one of the country's most comprehensive datasets on soil life; without the volunteers, a study of this scale across 1,000 sites would not have been possible.
- [15]
Without volunteers, collecting standardized information from 1,000 sites across an entire country would have been difficult and expensive for researchers.
- [16]
The research team clarified that underwear which nearly vanishes is not automatically evidence of a perfectly balanced ecosystem, because rapid decomposition can signal high fertility but may also reveal excessive nutrient levels.
- [17]
Because cotton is primarily made from cellulose, soil-dwelling organisms can gradually consume the material; the more fabric that disappeared, the more biologically active the soil was likely to be.
- [18]
More than half of global biodiversity is estimated to live below ground, and soil biodiversity is declining worldwide.
- [19]
The researchers propose an "underwear index" as an easy-to-understand way of illustrating soil processes and raising public awareness of the need to protect soils.
- [20]
The burial density was about two pairs of underwear per location.
- [21]
The tea bag burial density was about twelve bags per location.
- [22]
Roughly a quarter of the participating volunteers ended up on the author list.
- [23]
Neither the University of Zurich announcement nor the magazine coverage of the paper reports any result from the 12,000 buried tea bags; the described findings all concern the cotton underwear.
Sources
2 independent publishers whose own reporting we read for this story.
- discovermagazine.com2,000 Pairs of Buried Underwear Helped Measure Soil Health in This Unusual Experiment
1 article · August 27, 2026
- phys.orgBuried underwear shows land use is key to soil health
1 article · August 26, 2026
- sciencedaily.comWhy scientists asked 1,000 people to bury their underwear
1 article · August 27, 2026
Topics and entities
Topics
- Citizen Science
- Soil Biodiversity
- Soil health
Entities
- Plants, People, Planet
- Marcel van der Heijden
- Proof by Underpants
- University of Zurich