In 2021 researchers at the University of Zurich and Agroscope, the Swiss federal centre for agricultural research, asked the public for an unusual favour: bury your underpants. About a thousand volunteers took part, putting more than two thousand pairs of cotton briefs and twelve thousand tea bags into the ground at roughly a thousand places around the country. Everybody followed the same procedure. Two months later the pairs came back up, were photographed, and travelled to a laboratory together with a sample of the soil they had been lying in.
What came back was not uniform. Some pairs emerged barely marked; others had been reduced to seams and elastic. That spread is the measurement. Cotton is food for the organisms living underground, so how much of it disappears in two months is a readable stand-in for how busy those organisms are. Ranked by what was left, private gardens were the liveliest ground in the country, holding the most organic matter and the best conditions for earthworms, fungi and bacteria. Lawns were the least active of all. Cultivated fields and meadows sat between the two.
The result the team leads with is not that ranking but what best predicted it. Of everything recorded, how a plot was used, whether garden, meadow, field or lawn, explained the differences better than most of the soil's own properties did, although chemistry, and nutrient levels in particular, mattered as well. "Our results show that how soil is managed can significantly affect both soil life and soil quality," says Marcel van der Heijden, the UZH agroecologist who co-led the study. Keep the ground covered, add compost, vary the rotation, ease off fertiliser and pesticide: the levers are management ones.
Faster is not automatically better. Franz Bender of Agroscope, who co-led the project, cautions that maximum decomposition suits farmland but not every ecosystem: in forests, and in gardens too, cotton vanishing quickly can signal more nutrients than the place ought to be carrying. Ground that is cold or dry barely works at all. The study appears in Plants, People, Planet, and its authors want the method kept: an "underwear index" anybody can run in their own garden, which makes it the rare soil measurement people will actually talk about.