2,000 pairs of underwear buried in Switzerland revealed something startling

To show that soil on Earth has lost much of its nutrients, a team of scientists came up with a bizarre experiment. They buried 2,000 pairs of underwear across Switzerland in gardens and lawns, and then dug them up two months later. Some of them barely had any cloth left, while others only had one or two holes. The authors wrote that the "Proof by Underpants" project is "an easy-to-interpret tool, providing informative insights into the state of soils." It was published in the journal Plants, People, Planet.

"They are perfectly suited to raise attention in society for soil," they said. The study was carried out five years ago with 1,000 volunteers burying the underwear and 12,000 tea bags in different places in Switzerland. They were retrieved two months later and sent to the lab.

What no holes in underwear told about the soil

Scientists led by researchers at the University of Zurich said that the underpants with a lack of holes are a sign of missing nutrients in the soil. "Soils are rapidly degrading, threatening food production, biodiversity, and Earth system functioning," the researchers wrote.

In Switzerland, the lowest signs of biological activity were observed in lawns, croplands, and grasslands. Monocultures of grass around houses and buildings had the least fertile soil. Private gardens had the most active degraders - worms, fungi, bacteria, and other organisms - and the highest levels of organic carbon and nutrients. This is likely because such spaces are actively taken care of and nourished with fertilisers.

Around 58 per cent of the cotton in underwear planted in private gardens decomposed in two months. Meanwhile, in lawns, the percentage stood at 40, the least of all spaces.

Importance of soil

The topsoil helps provide 95 per cent of our food, and soil itself is the second-largest carbon reservoir on Earth. But as its quality deteriorates, society stands at risk of collapse. "This threat is largely unrecognised in broader society, hindering effective steps towards soil protection," they state in the study.

The researchers said that this can be reversed by changing how land is used. Land use was the single most important predictor of how well the underwear decomposed in the study.

Why use underpants for the study?

Simply because they are more "playful" and an "excellent outreach tool". The results have shown that better management of soil is crucial. "Our results show that how soil is managed can significantly affect both soil life and soil quality," co-leader of the study Marcel van der Heijden, an agroecologist at UZH, said.

The downside of the underwear study

Scientists cautioned that increased soil fertility isn't always a good sign. In private gardens, the presence of phosphorus, nitrogen, and potassium concentrations showed fertiliser use. Higher phosphorus levels threaten the waterways and local biodiversity. The Underwear Index shows "fertile" soils, which might not necessarily be healthier.