A buried pair of cotton briefs ranked 1,000 Swiss soils by biological activity

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.