What can a cotton undergarment buried in the ground reveal? More than most would expect. Scientists from the University of Zurich and Agroscope—the Swiss federal research center for agriculture—launched an unusual citizen science project called Proof by Underpants. They asked around 1,000 volunteers across Switzerland to bury more than 2,000 pairs of cotton underwear at roughly 1,000 different locations—from private gardens and farmland to meadows and lawns.
A Hidden World Beneath Our Feet
Two months later, participants dug up the garments, photographed them, and sent both the images and soil samples to the research team. Why underwear? Because cotton decomposes at a rate closely tied to biological activity in the soil: the faster it breaks down, the more active the underground ecosystem. In essence, the underpants served as simple, tangible indicators of life we rarely see—earthworms, fungi, bacteria, and countless other organisms that drive nutrient cycling and sustain soil fertility.
Soil is far more than just dirt beneath our feet. It stores water and carbon, holds essential nutrients, and hosts an estimated quarter of Earth’s biodiversity. Yet this subterranean world remains largely invisible—and often underestimated—in public awareness and policy.
What the Data Showed
The findings, recently published in the scientific journal Plants, People, Planet, revealed striking regional differences in decomposition speed. The highest biological activity was recorded in private gardens—places where organic matter levels were consistently higher, creating ideal conditions for soil organisms. In contrast, the slowest decomposition occurred on manicured lawns. Agricultural fields and pastures fell somewhere in between.
Most notably, land use emerged as the strongest predictor of decomposition rate—more influential than almost any measured soil property, including pH, texture, or moisture content. Whether a site was a garden, pasture, cropland, or lawn explained the variation better than traditional soil metrics.
Decomposition ≠ Health
Importantly, rapid decomposition doesn’t always mean ‘healthier’ soil. While high biological activity often signals rich nutrient availability—beneficial for crop production—it isn’t universally ideal. In natural or near-natural ecosystems, excessively high nutrient concentrations can actually indicate imbalance—for example, signs of eutrophication or disruption of native plant communities.
The project also included 12,000 standardized tea bags buried alongside the underwear, following the same protocol—a method previously used in global soil studies. Combining both approaches strengthened the reliability of the results and demonstrated how creative, accessible science can deepen public understanding of critical environmental systems.