1000 volunteers buried their underwear in 2021. 5 years later, here's why they are digging them back up

In 2021, the University of Zurich (UZH) and Agroscope, the Swiss federal research center of excellence for agricultural research, launched a project called "Proof by Underpants" (Beweisstück Unterhose), as part of which 1,000 Swiss citizens buried 2,000 pairs of white cotton underwear and 12,000 tea bags across different parts of the country. Marcel van der Heijden and Franz Bender were the two main scientists behind the project. Two months later, when researchers dug them up, they were shocked by how much they could learn about the soil through the underpants. Dutch Breaking News also covered the story on September 6, 2026, which received 148,000 views, 1,924 likes, and 29 comments.

Two-month burial

The Swiss discovered a new way to study soil health and its decomposition rates. The study, for which Heijden even won an Ig Nobel Prize in 2026, showed that land use was one of the most important predictors of the soil's decomposition rate and health. Two months after the underwear was buried, scientists dug them up and took photos, as well as soil samples from each location, and sent them to the laboratory for further analysis.

Private gardens showed the best results

The results were published in "Plant, People, Planet." It revealed that underwear buried in different locations decomposed at different rates. Those buried in private gardens decomposed quickly, while those in lawns were slower to deteriorate. Underwear buried in agricultural fields and meadows showed a medium decomposition rate. The reason it decomposed really fast in private gardens was due to the presence of a high level of organic matter. This included bacteria, fungi, and earthworms. Heijden said, "Our results show that how soil is managed can significantly affect both soil life and soil quality. Healthy, biologically active soil is crucial for fertility, nutrient cycling, and many other ecosystem services."

Methods to improve soil health

The study also shared a few ways to improve soil life. It recommended that the soil be covered at all times, compost be added from time to time, different crops be planted, and the use of mineral fertilizers and pesticides be minimized. However, Bender added, "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. In gardens, too, rapid decomposition of the underwear may point to an oversupply of nutrients." 

Dutch innovation

While viewers think the project is hilarious for using underwear, they appreciated the results that it brought. @ghacorreia wrote, "I hope there's a more efficient way to do this." @itsalexzeta wrote, "Finally some interesting news."

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