Soil may be hidden beneath our feet, but its biological activity could soon become one of the most visible indicators of ecosystem health—thanks to an unlikely scientific instrument: a pair of cotton underpants. A nationwide citizen-science experiment in Switzerland has shown that the rate at which buried cotton underwear decomposes can reveal major differences in soil activity, fertility and land management. The project, known as Proof by Underpants, involved approximately 1,000 volunteers who buried more than 2,000 pairs of cotton underwear and 12,000 tea bags at sites distributed across the country. After two months underground, participants excavated the materials, photographed the remains and submitted them, together with soil samples, for scientific analysis. The resulting dataset offers one of the most extensive assessments of soil biological activity ever assembled in Switzerland and transforms a deliberately playful experiment into a potentially valuable tool for environmental monitoring.
The logic behind the method is straightforward but scientifically meaningful. Cotton is composed primarily of cellulose, a complex carbohydrate that forms the structural framework of plant cell walls. In soil, cellulose becomes a source of carbon and energy for a broad community of microorganisms, including bacteria and fungi, while larger organisms such as earthworms help physically fragment the material and distribute it through the soil. As decomposition proceeds, enzymes produced by microbes break long cellulose chains into smaller molecules that can be metabolized or incorporated into the soil carbon cycle. A cotton garment therefore acts as a standardized organic substrate. If it is heavily damaged after a fixed burial period, the soil community has likely been biologically active. If it remains largely intact, decomposition may have been constrained by low microbial abundance, limited moisture, unfavorable temperatures, poor organic-matter availability or other environmental conditions.
The results, published in the journal Plants, People, Planet, showed that decomposition rates varied substantially from one location to another. Underwear buried in private gardens generally broke down most rapidly, while material placed in lawns decomposed the slowest. Agricultural fields and meadows occupied an intermediate position. The differences were not simply a matter of geography. Instead, the researchers found that land use was the strongest factor associated with how quickly the cotton disappeared. Gardens contained the highest levels of organic matter, creating favorable conditions for decomposers. Organic matter supplies both food and habitat for soil organisms, improves the structure of soil aggregates and helps retain water. Together, these effects can support a more active and diverse biological community capable of processing plant residues and other carbon-containing materials at a faster rate.
The contrast between gardens and lawns is particularly revealing because both may appear green and healthy from the surface. A lawn, however, is often managed as a relatively uniform system. Repeated mowing removes plant material, vegetation is frequently composed of only a few grass species, and soils can become compacted through foot traffic or machinery. In some settings, irrigation and fertilizer applications create additional chemical and physical pressures. Private gardens, by comparison, may receive compost, leaf litter and other organic inputs, while containing a mixture of plants with different root systems. These roots release carbon compounds into the surrounding soil and create channels that improve aeration and water movement. The result can be a more complex habitat for bacteria, fungi, earthworms and other organisms involved in decomposition.
The findings matter because soil is not merely an inert medium in which crops grow. It is a living system that stores water, carbon and nutrients while supporting a substantial proportion of the planet’s biodiversity. More than half of global biodiversity is estimated to exist below ground, where organisms drive processes that determine whether nutrients remain available to plants, whether carbon is retained or released and whether soils resist erosion and drought. When biological activity declines, the consequences can extend far beyond the soil itself. Reduced microbial function may slow nutrient cycling, weaken soil structure and limit the ability of agricultural land to sustain production. In contrast, biologically active soils can improve fertility, promote decomposition of organic residues and contribute to ecosystem services that support both food security and climate resilience.
The researchers emphasized that fast decomposition is not automatically a sign of perfect soil health. In agricultural systems, rapid breakdown may indicate strong biological activity and a generous supply of nutrients—conditions that can benefit crop production. But in forests and other near-natural habitats, unusually rapid decomposition may reflect nutrient enrichment and a disruption of the ecosystem’s natural balance. Excessive nutrient inputs can alter plant communities, stimulate particular microbial groups and cause the loss of species adapted to nutrient-poor conditions. Gardens can face a similar problem when fertilizers or compost are applied in excessive quantities. In such cases, a rapidly decomposing pair of cotton underwear may indicate not only abundant soil life but also an oversupply of nutrients. The biological signal must therefore be interpreted in relation to land use, soil chemistry and ecological context.
The study also identified temperature and moisture as important controls on soil activity. Microbial metabolism generally slows when soils become cold, while drought limits the water required for biochemical reactions and restricts the movement of nutrients. Under extremely dry conditions, many soil organisms enter dormant states, sharply reducing decomposition. Excess water can create a different problem by filling soil pores and limiting oxygen, which may suppress organisms that depend on aerobic respiration. These factors help explain why identical cotton garments can produce very different results even when buried in similar landscapes. The underwear test does not measure a single organism or one isolated chemical property. Instead, it integrates the effects of multiple biological and environmental processes over a defined period, making it a broad indicator of the functioning of the soil community.
Based on the experiment, the researchers propose an “underwear index” as an accessible way to communicate soil processes to the public. Conventional soil assessments often require laboratory equipment and specialized measurements, such as microbial respiration, enzyme activity, organic-carbon concentration, nutrient availability or DNA-based analysis of soil communities. Those techniques remain essential for detailed research, but they can be difficult to explain outside scientific settings. A pair of cotton underpants offers an immediate visual signal: the more fragmented and decomposed the fabric, the more actively soil organisms have been processing cellulose under the prevailing conditions. The approach is not intended to replace laboratory diagnostics, and decomposition alone cannot provide a complete measure of soil health. Its power lies in combining a standardized field experiment with an image that makes an invisible ecological process understandable.
The scale of Proof by Underpants was made possible by the volunteers who carried out the same basic procedure across roughly 1,000 locations. Their participation produced samples from different regions, land-use types and environmental conditions that would have been difficult for a small professional research team to collect independently. Around 240 citizen scientists were listed as co-authors of the resulting publication, reflecting the unusual degree to which the public contributed not only observations but also to the scientific record. Participants received individual feedback, including soil-analysis results, evaluation tools and suggestions for more sustainable soil management. The project demonstrated how a memorable experiment can attract attention to an overlooked ecosystem while generating data with genuine scientific value.
The Swiss results point toward practical strategies for protecting soil life. Maintaining continuous plant cover can reduce erosion and moderate temperature and moisture fluctuations. Adding compost or other organic amendments can increase carbon availability, although applications should be matched to the needs of the site. Diversifying crop rotations can interrupt disease cycles and create a wider range of root-derived resources for soil organisms. Limiting unnecessary mineral fertilizers and pesticides may reduce chemical pressures that affect microbial and invertebrate communities. None of these measures works identically in every landscape, and rapid decomposition must always be interpreted alongside nutrient levels, moisture, temperature and land-use history. Even so, the buried-cotton experiment offers a striking reminder that soil health is measurable not only through complex instruments, but also through the quiet work of organisms that transform a simple piece of fabric beneath the ground.
Subject of Research: Soil biological activity, soil health, decomposition and land management
Article Title: Soil Health Assessment Using Buried Cotton Underpants with the Help of 1000 Citizen Scientists
News Publication Date: 26 August 2026
Web References: Proof by Underpants project: http://www.beweisstueck-unterhose.ch/
References: S.F. Bender, D. Bürge, L. Bragazza, E. Knop, S. Masson, N. Peter, R. Dmarmels, D. Müller, A. Imhof, P. Viviani, A. Bieri, T.D. Bucheli and M.G.A. van der Heijden, “Soil Health Assessment Using Buried Cotton Underpants with the Help of 1000 Citizen Scientists,” Plants, People, Planet, published 25 August 2026.
Image Credits: Nicolas Zonvi
Keywords: Soil health, soil bacteria, soil biodiversity, decomposition, citizen science, land management, environmental science, cotton underwear, soil fertility, Switzerland
