In 2021, 1,000 Swiss volunteers buried 2,000 pairs of cotton underpants to test soil life. 5 years later, results from 12,000 teabags showed which soils were most active

In 2021, two thousand pairs of white cotton underpants went into the ground across Switzerland. A thousand citizen scientists joined researchers from Agroscope and the University of Zurich, burying standard underwear alongside twelve thousand teabags. The goal was straightforward: measure how quickly hungry soil organisms consume organic material to assess the hidden health of Swiss ground.

When researchers dug up the fabric, human management mattered far more than natural geology. Private vegetable gardens proved to be the absolute hotspot for biological activity, breaking down cotton and teabags at rapid speed. High organic carbon, regular composting, and deep plant roots created thriving underground communities. At the opposite extreme sat manicured lawns, where frequent mowing and soil compaction left underground microbes severely starved.

Speed alone does not tell the whole story. In some private gardens, hyperactive decomposition stemmed from an oversupply of synthetic fertilizers, which can actually disrupt natural nutrient balances over time. Still, the lesson for everyday gardeners remains clear. Keeping soil covered, adding rich compost, avoiding chemical sprays, and encouraging diverse plant species will easily breathe real life back into quiet ground.

What were scientists trying to measure?

The project focused on the enormous amount of life hidden beneath the ground. More than half of Earth's global biodiversity is estimated to exist underground. Yet biological activity varies considerably from one soil environment to another.

That difference can be difficult for ordinary people to see. Soil may look similar on the surface, even when the communities living inside it differ greatly. The buried underwear offered volunteers a visible and slightly unusual way to document those differences.

The study was run by the University of Zurich together with a Swiss federal agricultural research organization. Instead of keeping the work inside a laboratory, researchers spread the experiment across real landscapes. Volunteers became part of the data-gathering process in their own communities.

How did the underwear experiment work?

Each volunteer prepared a small underground test site measuring roughly 60 by 30 by 30 centimeters. Two new pairs of organic men's white briefs were placed underground at each location. Participants also buried 12 nonwoven polypropylene tea bags alongside the underwear.

The researchers chose sites mainly in populated areas outside Switzerland's mountainous regions. That gave the project access to a broad range of everyday soils. The locations also allowed scientists to compare conditions across different types of land.

The experiment had two checkpoints. After 30 days, volunteers removed one pair of underwear and six tea bags. The remaining underwear and tea bags stayed underground for another month before being collected at 60 days.

Why bury tea bags alongside underwear?

The tea bags provided another way to examine decomposition underground. Unlike the underwear, the tea bags were made from nonwoven polypropylene, which behaves differently from cotton in soil.

That difference gave researchers another material to track during the experiment. Together, the underwear and tea bags created simple indicators of what was happening below the surface. Volunteers could collect the materials at set intervals rather than relying only on laboratory measurements.

The approach also made the research easier for members of the public to understand. Instead of being asked to think about invisible microbial activity, participants could watch physical materials change underground.

What does the underwear reveal about soil?

The central idea is that disappearing cotton can provide clues about biological activity in soil. Cotton contains cellulose, which soil organisms can break down as they feed and grow. More active communities of organisms can therefore leave greater evidence of decomposition.

That does not mean every rapidly decomposing pair of underwear automatically proves that soil is healthier. Soil is an extraordinarily complicated environment, with many organisms and chemical processes interacting beneath the surface.

The project instead offers a practical way to compare different locations. A pair of briefs placed in two different soils can experience noticeably different conditions over the same period. Those differences become easier to observe once the fabric is brought back above ground.

The scale of the experiment would have been difficult to achieve at a handful of research stations. About 1,000 volunteers helped researchers place and recover the materials across Switzerland. Their participation created a much wider collection of observations from real-world soils.

Citizen science also changed the relationship between researchers and participants. Volunteers were not simply watching a scientific experiment from the sidelines. They were collecting evidence themselves and helping researchers understand the ground beneath familiar landscapes.

That is especially useful for soil research because underground ecosystems can vary across surprisingly short distances. A garden, field or grassland can have different conditions even when they sit within the same broad region.

What could this tell us about the world beneath our feet?

The underwear project highlights a problem that is easy to overlook. People spend most of their time looking at landscapes from above, while much of the biological activity happens underground.

Soil supports plants, stores organic material and provides habitat for countless organisms. Yet those underground communities remain difficult to observe without disturbing the ground or conducting specialized tests.

The Swiss experiment does not turn underwear into a complete soil-health test. Instead, it shows how an ordinary material can make an invisible process easier to observe. That simplicity may be the most useful part of the experiment.

For Americans, the idea has an obvious everyday connection. The same questions can apply to gardens, lawns, farms and other managed landscapes across the United States. What looks like ordinary dirt from above can contain a surprisingly active world underneath.

The Swiss volunteers began with something almost comically simple: bury a pair of underwear and wait. What came back out offered researchers another window into that hidden world. The fabric was never the real subject. The organisms breaking it down were.