Researching soil health with tea bags and underpants

In April 2021, researchers from Agroscope and the University of Zurich are launching a nationwide citizen science project.

The goal is to systematically record soil health across Switzerland. It is the largest project of its kind in the country so far. Between Geneva and the Engadin, a total of 2’000 samples will be collected and measurements taken.

The more decomposed the underpants, the healthier the soil

The project, titled “Exhibit A: Underpants”, uses a somewhat unconventional measurement method. The first 1’000 registrants will receive a package containing two pairs of cotton underpants. For all other interested participants, instructions will be provided on how to carry out the tests independently. The underpants are buried in a field, meadow, or garden. After two months, they are dug back up. The faster the cotton underpants decompose, the more living organisms are active in the soil — and the healthier the soil. That, at least, is the hypothesis being tested in the project. Thanks to this initiative, far more data can be collected than would be possible if the researchers had to do everything on their own.

Comparing tea bags with underpants

Underpants have already been used for several years in Canada by farmers as a simple indicator of soil health. “However, no one has yet verified whether this method also meets scientific standards. Nobody knows how accurate it is or whether there is actually a clear relationship between the decomposition rate of the underpants and soil quality”, says project lead Marcel van der Heijden, ecologist at Agroscope and the University of Zurich. To find out, participants additionally bury various tea bags. “These are well established in soil research. We know how long it takes for different types of tea to decompose. We can then compare this with the cotton in the underpants», says Franz Bender, project leader. The decomposed underpants are photographed and analysed digitally. «This allows the degree of decomposition to be determined precisely», says Bender. The volunteer citizen researchers also take a soil sample, which can provide additional information about soil quality.

The world's most valuable resource is under threat

Without soil, life on Earth would not be possible for us humans. Soil is the foundation for food production and raw materials, filters water and protects against natural hazards. It is also home to trillions of the smallest living organisms, which account for a quarter of global biodiversity. Their abundance and productivity are the hallmarks of healthy soils.Yet this most valuable of all resources is severely threatened worldwide, including in Switzerland. Erosion, excessive use of agrochemicals and pesticides and urban sprawl reduce productive land every single day. Every year, an area two and a half times the size of Switzerland is so severely degraded worldwide that agriculture can no longer be practised on it. More on the topic of environment and nature conservation.