Why Scientists Asked More Than 1,000 People to Bury Their Underwear to Study Soil Biodiversity Across Switzerland

More than 1,000 people across Switzerland were given an unusual scientific assignment: bury their underwear.

The volunteers placed cotton underwear in soil at locations across the country, left it underground for two months, and then dug it back up. What happened to the fabric gave researchers a surprisingly simple way to investigate what was happening beneath the ground.

The experiment, led by researchers from the University of Zurich and Agroscope, was part of a citizen-science project designed to examine biological activity in different types of soil. More than 2,000 pairs of cotton underwear were buried at around 1,000 sites, giving scientists a large collection of samples from gardens, lawns, agricultural land, and meadows.

The strange-looking experiment had a serious purpose. Soil is filled with organisms that are constantly breaking down organic material, but much of that activity is invisible from the surface. Cotton provided researchers with something they could bury, retrieve, and compare.

Why Underwear Makes a Useful Scientific Tool

Cotton fabric is made largely from cellulose, an organic material that microorganisms can break down.

As bacteria, fungi, and other soil organisms feed on organic material, they contribute to its decomposition. The more extensively a cotton item breaks down, the more evidence researchers have of biological activity in the surrounding soil.

That does not make a pair of underwear a complete measure of soil health. Soil health is influenced by many factors, including its physical structure, chemistry, nutrients, and biological communities.

But the fabric offers something useful: a standardized object that can be placed in many different environments and examined after the same period of time.

It also makes an otherwise complicated subject easier for people to see.

Instead of being told that one patch of soil contains more biological activity than another, volunteers could simply look at how much of the underwear remained.

Gardens Had Faster Decomposition Than Lawns

When the volunteers dug up the underwear, the condition of the fabric varied depending on where it had been buried.

The researchers found that garden soils generally showed faster decomposition than lawns, while agricultural fields and meadows fell between the two. The differences suggested that how land is managed can have a substantial effect on the biological activity taking place underground.

Garden soils also tended to contain more organic matter and conditions that supported active soil communities.

Lawns, meanwhile, are often managed in ways that create a more uniform environment, including regular mowing and, in some cases, fertilisation or other treatments.

The findings do not mean that every garden automatically has better soil than every lawn. Soil conditions can vary considerably from one location to another.

Instead, the results point to the importance of land management in shaping the organisms living underground.

Faster Breakdown Does Not Always Mean Healthier Soil

The underwear experiment comes with an important scientific caveat.

It might seem logical that the underwear that decomposed fastest came from the healthiest soil. But the researchers caution against making such a simple conclusion.

Rapid decomposition can indicate strong biological activity and a plentiful supply of organic material. However, extremely high nutrient levels or biological activity are not necessarily beneficial in every ecosystem.

For example, natural ecosystems can be disrupted when nutrient levels become unusually high. Garden soil can also receive more fertilizer or organic material than it actually needs.

Other conditions matter, too. Temperature and moisture influence how active soil organisms are, meaning the same piece of cotton could decompose differently under different environmental conditions.

The underwear, therefore, works best as a clue rather than a definitive health test.

Thousands of Volunteers Helped Scientists Study Soil

The scale of the experiment would have been difficult for researchers to achieve on their own.

Around 1,000 citizen scientists took part, burying more than 2,000 pairs of underwear and thousands of tea bags using standardised methods. After two months, they retrieved the materials, photographed them, and provided information about the sites where they had been buried.

That gave researchers access to soil samples from a wide range of locations and land-use types across Switzerland.

The project also turned participants into active contributors to the research rather than simply observers. About 240 citizen scientists were credited as co-authors of the resulting study.

That level of participation matters because soil can vary substantially over relatively short distances. Having people collect samples from many locations allowed researchers to examine those differences on a much larger scale.

What Soil Microbes Are Doing Beneath Our Feet

The experiment also offers a reminder that soil is far from lifeless.

Bacteria, fungi, earthworms, and other organisms help break down dead plants and other organic material. Through that process, nutrients are released and recycled within ecosystems.

Those microscopic and often overlooked communities support plant growth and contribute to the wider functioning of ecosystems.

Scientists are increasingly interested in soil biodiversity because changes in the organisms living underground can affect agriculture, nutrient cycling, and ecosystem stability.

Yet measuring that biodiversity across large areas is not always straightforward.

That is where a simple piece of cotton can become useful.

An Unusual Experiment with a Serious Purpose

The researchers’ approach was deliberately simple enough for members of the public to participate in while still producing information that could be analyzed scientifically.

The team hopes methods such as this could help make soil biological activity easier to monitor and communicate. The researchers have even discussed the possibility of developing an “underwear index” that could provide a simple way of comparing decomposition and biological activity in different soils.

The idea is memorable because the object is so ordinary.

But beneath the novelty is a useful scientific question: what can the breakdown of a simple piece of cotton tell us about the living world beneath our feet?

In Switzerland, more than 1,000 volunteers helped provide an answer, one buried pair of underwear at a time.