Soil supports the food we eat, stores water, carbon, and nutrients, and provides a habitat for much of the life on Earth. Scientists estimate that more than half of the planet’s biodiversity exists below ground. Yet soil biodiversity is declining worldwide, putting agriculture, food security, and essential ecosystem functions at risk.
To explore this hidden ecosystem, researchers from the University of Zurich (UZH) and Agroscope, the Swiss Federal Center of Excellence for Agricultural Research, launched the citizen science project Proof by Underpants (Beweistück Unterhaus). The project was created to raise public awareness of soil ecosystems while collecting valuable scientific data on soil health and biological activity.
Using the same standardized method, 1,000 volunteers buried more than 2,000 pairs of cotton underwear and 12,000 tea bags at approximately 1,000 locations across Switzerland. After two months, participants dug up the materials, photographed them, and sent the samples, along with soil, to a laboratory for analysis.
Cotton underwear reveals soil biological activity
The survey produced an extensive map of biological activity in Swiss soils. Researchers discovered that cotton underwear decomposed at significantly different rates depending on the location where it was buried.
The rate of decomposition provided a simple indicator of underground biological activity. When microbial activity is high, soil organisms break down cotton more quickly.
Private gardens recorded the fastest decomposition rates. Researchers also found that garden soils contained the greatest amounts of organic matter, creating favorable conditions for earthworms, fungi, bacteria, and other beneficial soil organisms.
Lawns showed the lowest levels of soil biological activity. Farmland and meadows fell between private gardens and lawns in terms of decomposition and soil activity.
Land use has a major impact on soil health
“Our results show that the way soil is managed can have a significant impact on soil longevity and quality,” says co-research leader Marcel van der Heijden, professor of agroecology at UZH. “Healthy, biologically active soils are essential for fertility, nutrient cycling, and many other ecosystem services.”
Several land-management practices can help support soil biodiversity. These include keeping soil covered year-round, adding compost, using more diverse crop rotations, and reducing reliance on mineral fertilizers and pesticides.
Among all the factors studied, land use had the strongest influence on underwear decomposition. Whether an area was a garden, meadow, cropland, or lawn explained differences in decomposition more effectively than most of the soil properties measured by researchers.
Soil chemistry also played an important role. Nutrient concentrations, for example, had a significant effect on the level of biological activity in the soil.
Faster decomposition is not always better
Rapid cotton decomposition was often linked to fertile soil and a plentiful supply of nutrients. In agricultural areas, these conditions can benefit plant growth and crop production.
“However, maximum decomposition is not desirable in every ecosystem,” says co-project leader Franz Bender, head of Agroscope’s agroecology assessment team.
“In near-natural habitats such as forests, very high nutrient levels may signal a natural nutrient imbalance. Even in gardens, rapid underwear decomposition could indicate an excess of nutrients,” Bender explains.
When this occurs, gardeners may need to reconsider how much fertilizer they apply. Soil biological activity is also strongly affected by temperature and moisture. Cold or excessively dry conditions can significantly slow the activity of soil organisms.
An “underwear index” could help measure soil health
The experiment demonstrates that burying cotton materials can provide a simple and practical way to compare the biological activity and fertility of different soils.
Researchers are proposing the development of an “underwear index” to help the public understand soil processes and recognize the importance of protecting healthy, biologically active soils.
Citizen scientists create a national soil dataset
The Proof by Underpants project also highlights the importance of citizen science. Covering approximately 1,000 locations across Switzerland would not have been possible without the support and participation of so many volunteers.
Because samples were collected across all regions of the country, the project created one of Switzerland’s most comprehensive datasets on soil organisms and soil biological activity.
The scale of public participation is also reflected in the study’s authorship. Approximately 240 citizen scientists are listed as co-authors of the publication.
In recognition of their contribution, volunteers received personalized feedback, including soil analysis results, assessment tools, and recommendations for managing soil more sustainably.
Source: www.sciencedaily.com