In a unique citizen science project, 1,000 volunteers from 25 countries buried organic cotton underpants and tea bags to assess soil decomposition rates. Led by Van der Heijden et al., participants followed detailed protocols to dig holes, insert the garments vertically with waistbands exposed, and add six tea bags for comparison. After 30 and 60 days, volunteers excavated the items and mailed samples to researchers.

The study found land use was the most critical factor in decomposition speed. Underpants decomposed fastest in private gardens, which featured high organic matter and robust soil organism activity including earthworms and fungi. Lawns showed the least activity, while agricultural fields and meadows fell in between.

Temperature, moisture, and nutrient levels also influenced the rate of breakdown. Researchers concluded that the "underpants index" provides meaningful soil data comparable to traditional biological indices, offering a direct visual and haptic measure that is easier to interpret. The method proves ideal for citizen science projects and raising awareness about soil health.

DOI: Plants People Planet, 2026.