Volunteers bury their underpants for filthy experiment on soil health

By the Editorial Team · Saturday, August 29, 2026

Researchers at the University of Zurich mobilized 1,000 volunteers to bury and later exhume over 2,000 pairs of cotton underwear across Switzerland to measure soil biological activity through decomposition rates. The resulting soil activity map highlights regional differences in soil health, offering valuable insights for future soil conservation and sustainable land management efforts.

A team of researchers at the University of Zurich conducted a nationwide citizen science experiment to assess soil health across Switzerland using an unconventional method: burying cotton underwear. Launched in 2021, the project titled “Proof by Underpants” involved 1,000 volunteers who buried more than 2,000 pairs of cotton underwear and 12,000 tea bags at approximately 1,000 sites throughout the country.

After a period of two months, the participants exhumed the underwear, which was then photographed and sent for laboratory analysis alongside collected soil samples. The study aimed to evaluate soil biological activity by measuring the rate at which soil organisms decomposed the cotton fabric. Faster decomposition rates indicate higher biological activity and soil fertility, as more active soil fauna and microbes break down organic material more efficiently.

The results were compiled into a comprehensive soil activity map, published recently in the journal Plants, People, Planet. The map revealed significant variation in decomposition rates across different locations, reflecting differences in soil health and ecosystem function within Switzerland's diverse environments.

According to the researchers, using cotton underwear provided a novel but effective proxy for assessing soil biology because cotton is a natural, uniform material that decomposes primarily through microbial and invertebrate activity. The inclusion of tea bags, which decompose differently, further enriched the data by offering a complementary decomposition metric.

This large-scale volunteer engagement highlights the potential for citizen science initiatives to contribute data for environmental monitoring and land management strategies. By involving the public in this hands-on experiment, scientists were able to gather extensive data on soil ecosystems across a broad geographic area, improving the understanding of soil fertility patterns in Swiss soils. The findings may inform future efforts to promote soil conservation and sustainable land use practices.

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