Thousands of Buried Underwear Reveal How Land Use Shapes Soil Life

Cotton underwear became an unlikely scientific tool in Switzerland, where more than 1,000 volunteers buried over 2,000 pairs at sites ranging from gardens and lawns to agricultural fields and meadows. According to reporting by Phys.org, the participants followed a standardized procedure: After two months underground, they dug up the underwear, photographed it and sent it to researchers along with soil samples. The project, called “Proof by Underpants,” was launched in 2021 by the University of Zurich and Agroscope, Switzerland’s federal agricultural research center. The researchers used the condition of the cotton fabric as an indicator of biological activity. Soil organisms such as earthworms, fungi and bacteria consume and break down organic material, so faster decomposition suggested greater activity in the soil. The underwear decomposed most rapidly in private gardens, where researchers found the highest levels of organic matter. It broke down least in lawns, while agricultural fields and meadows produced intermediate results. The study found that land use explained differences in decomposition better than most of the other soil properties measured. Chemical characteristics, including nutrient levels, also influenced the results. Rapid decomposition can indicate fertile soil and a strong supply of nutrients, which may benefit agricultural production. But the researchers cautioned that faster breakdown is not automatically better in every setting. In forests and other near-natural habitats, unusually high nutrient levels may signal disruption of the normal nutrient balance. The same pattern in gardens could indicate that too much fertilizer is being used. Temperature and moisture were also important. Soil organisms were less active when conditions were especially cold or dry. The findings, published in the journal Plants, People, Planet, support the researchers’ proposal for an easy-to-understand “underwear index” to demonstrate soil processes and raise awareness of soil health. They also illustrate how citizen scientists can contribute to large-scale research: Volunteers collected information from around 1,000 sites throughout Switzerland, creating what the researchers described as one of the country’s most comprehensive datasets on soil life. Around 240 participants were listed as co-authors of the resulting publication. The researchers identified practices that can support soil life, including keeping soil covered, adding compost, diversifying crop rotations and limiting mineral fertilizers and pesticides.