The “Pants Index” Uses Cotton Underwear to Measure Soil Health
Prisca Kohler, Agroscope
Cotton underwear that is more heavily decomposed indicates higher activity from soil microorganisms.
Prisca Kohler, Agroscope
Prisca Kohler, Agroscope
More than 2,000 cotton underwear samples were buried in fields, gardens, lawns, and meadows to study soil decomposition.
Prisca Kohler, Agroscope
Cotton underwear that is more heavily decomposed indicates higher activity from soil microorganisms.
Prisca Kohler, Agroscope
More than 2,000 cotton underwear samples were buried in fields, gardens, lawns, and meadows to study soil decomposition.
Prisca Kohler, Agroscope
Scientists have developed a simple way to measure soil health: burying cotton underwear and tracking how quickly it decomposes. Known as the “Pants Index,” the method provides a visible indicator of microbial activity in soil.
Van der Heijden and colleagues recruited 1,000 volunteers across 25 countries. The project included 240 participants as co-authors on the resulting paper. Each volunteer received an activity kit containing two pairs of organic cotton underwear, 12 tea bags, and supplies for collecting soil samples, along with detailed instructions.
Participants selected a location, collected a soil sample, and dug a hole. They then buried the two pairs of underwear vertically, leaving the synthetic waistband above the soil. Six tea bags were buried nearby to support a comparison with the established Tea Bag Index, or TBI, another method used to assess decomposition rates and soil biological activity.
After 30 days, volunteers recovered the first pair of underwear and its corresponding tea bags. The second pair was collected after 60 days. Participants documented the condition of each item before sending the materials to researchers for further analysis.
The results showed that land use was the strongest factor affecting decomposition. Cotton underwear decomposed fastest in home gardens, where soil samples also contained the greatest amount of organic matter. These conditions supported active communities of earthworms, fungi, bacteria, and other soil organisms.
Lawns showed the lowest level of biological activity, while farmland and pasture fell between gardens and lawns. Temperature, moisture, and soil nutrient levels also influenced decomposition, particularly when conditions were unusually cold or dry.
Researchers concluded that the Pants Index can reveal important information about soil conditions, including biological activity, moisture, nutrient availability, and other chemical and physical properties. Unlike the Tea Bag Index, which relies primarily on measuring changes in tea bags, cotton underwear provides a direct visual and tactile measure of decomposition.
Because the results are easy to understand, the researchers say the Pants Index could be particularly useful for citizen science projects and environmental education. The method also offers a memorable way to raise awareness about soil biodiversity and the importance of healthy soils.
Plants, People, Planet, 2026. DOI: 10.1002/ppp3.70259 (About DOI).
Source: arstechnica.com