Swiss study finds buried underpants rival teabags in measuring soil health
A national citizen science project involving 1,000 volunteers has validated a new "underpants index" for assessing soil decomposition, offering a more accessible alternative to standard laboratory methods.
A study published in the journal Plants People Planet reveals that organic cotton underpants can serve as an effective proxy for measuring soil health across Switzerland. The research, led by agroecologist Marcel van der Heijden of the University of Zurich, involved 1,000 citizens who participated in a national project dubbed "Proof by Underpants". The initiative aimed to map soil conditions by tracking the decomposition rates of organic matter in various land use environments.
Participants were provided with activity packs containing two pairs of organic cotton men’s underpants and 12 teabags. Volunteers buried the garments vertically alongside the teabags at selected sites, retrieving the first set after 30 days and the second after 60 days. The collected materials were then mailed to researchers for analysis. Notably, 240 of the participants were listed as co-authors on the resulting paper, highlighting the collaborative nature of the citizen science effort.
The findings indicate that land use is the primary factor influencing decomposition rates. Private gardens exhibited the fastest breakdown of the cotton, a result attributed to higher levels of organic matter that support diverse soil organisms such as earthworms, fungi, and bacteria. In contrast, lawns showed the least biological activity, while agricultural fields and meadows recorded intermediate levels of decomposition.
The study also accounted for environmental variables, noting that temperature, moisture levels, and soil nutrient concentrations significantly affect organism activity. Extreme cold or dry conditions were found to slow the process, reinforcing the complex interplay between management practices and natural factors in determining soil quality.
The researchers compared their new "underpants index" against the standard teabag index (TBI), a common method that typically requires precise tools like a fine scale balance. The underpants index proved equally effective in providing meaningful information about soil conditions, including chemical and physical properties. Furthermore, the method offers a direct visual and tactile measure of decomposition, making it easier for non-specialists to interpret the results.
According to van der Heijden, the results demonstrate that soil management significantly affects both soil life and quality. The authors suggest that the underpants method is an ideal tool for future citizen science projects, as it raises public awareness of soil-related issues while providing robust data on ecosystem services such as nutrient cycling and fertility.
