Two patches of soil may look almost identical from above to our eyes. Both show grass and other plants and receive rainfall. Yet beneath the surface, very different phenomena may be unfolding. At first glance, they’re hard to distinguish.
A question then arises that affects farmers, gardeners, and, in fact, anyone who depends on cultivated food: how do we figure out whether that thin layer of soil is functioning properly? Much of what matters remains hidden. Color, texture, or vegetation offer clues, but they’re not enough to reveal the constant activity that keeps that tiny universe running.
According to Plants, People, Planet, a team coordinated from Agroscope, the Swiss center for agricultural research, decided to tackle the problem with a strategy so simple it almost sounds like a joke: they recruited citizens from across the country and asked them to bury cotton underwear. Those garments were to serve as witnesses to something that continuously unfolds beneath our feet.
A Living Soil Is Hungry
Before digging anything up, it’s useful to understand what they aimed to observe. Soil isn’t just the brown support where plants take root. It harbors bacteria, fungi, small animals, and other organisms that form a community of enormous complexity.
Decomposition is precisely the process of turning complex materials —fallen leaves, wood, or carcasses— into simpler substances. For that reason, it is a key component of both soil fertility and the cycles of carbon and the elements plants need. The experts considered that such a process offered an indicator of how that community functions.
The underwear provided a kind of standardized snack for that underground machinery. The fabric was organic cotton and, save for seams and the waistband, consisted of biodegradable material.
The choice was not decorative: everyone was to receive essentially the same substrate to enable subsequent comparisons. Cotton mostly contains cellulose, a compound made of long chains of sugars that many microorganisms can break down.
The underwear provided a kind of standardized snack for that underground machinery: the fabric was organic cotton, which contains mainly cellulose, long chains of sugars that many microorganisms can break down.
Humidity, temperature, chemical composition, management practices and physical characteristics all exert influence. But, if we provide the same food for the same interval in many places, how much remains afterward offers a clue about the intensity of that living machinery. That was the bet.
Then They Distributed 2,000 Pairs of Underwear Across Switzerland
The extravagance was accompanied by a considerably less comic protocol. About 1,400 people volunteered in a few days. The organizers selected roughly a thousand with wide geographic distribution.
Each participant received two white units of organic cotton, twelve tea bags, a bag to collect soil and detailed instructions. They were to dig a hole, place the two garments vertically and cover them to about eight centimeters deep, with the waistband sticking out. Alongside them they would insert green tea and rooibos.
They were to dig a hole, place the two garments vertically and cover them to about eight centimeters in depth, with the waistband exposed; alongside them, they inserted green tea and rooibos.
The package thus turned a domestic gesture into a repeatable procedure: identical clothing, shared guidelines and equivalent exposure periods.
Why tea? Ecology already has the Tea Bag Index, a procedure that uses bags containing plant materials of known composition to study how their degradation progresses.
After roughly thirty days, the volunteers retrieved the first garment and its corresponding bags. A month later they did the same with the second. Everything returned to Agroscope, where the team examined it alongside the collected samples. The domestic trick had become a country-wide distributed trial.
Two Months Later, Some Underwear Had Almost Vanished
That was the moment to find out what had happened. By the end of the first month, the garments had on average lost about 10.1 percent of their length. After two months, the figure rose to 50.45.
It was necessary to translate such a spectacle into figures. They cleaned the remnants, opened each piece from the sides and laid it flat on a blue background. Then they took photographs from a fixed height and used digital image analysis to calculate how many pixels still corresponded to the fabric.
They also measured weight loss. Both magnitudes correlated strongly, though the area proved more reliable because soil particles sticking to the fabric could alter the scale. Thus was born the Underpants Index; literally, the Underpants Index: the proportion lost relative to a new piece.
The snack had done its job. Its diners remained hidden, but the feast left a quantifiable trace. Moreover, the underwear index correlated significantly with the tea bag index.
Gardens Consumed the Underwear; Lawns, Much Less
The main surprise emerged when comparing sites. Land use was the factor that best explained the uneven disappearance of the fabric. The link mattered: it indicated that the test responded to local characteristics rather than reflecting random deterioration.
Private gardens topped the ranking: after two months they had consumed, on average, about 58 percent of each piece. At the opposite end were lawns, with around 40 percent. Cultivated fields reached about 51 and permanent pastures 47.
Private gardens had consumed about 58 percent of each piece; cultivated fields, over 51; permanent pastures, 47; and lawns, around 40.
The measurements provided context. Private gardens showed the highest average soil organic carbon concentrations, around 3.4 percent, and elevated abundance of certain nutrients. Lawns and cultivated lands, by contrast, hovered around 2.1 percent soil organic carbon.
That dispels a seductive intuition. A perfectly trimmed green carpet may seem healthy to us, while a somewhat messy garden communicates less tidiness. Its appearance does not necessarily reveal how much activity lies beneath. To know that universe, you have to look at what it does, not merely how it looks.
But Underwear Cannot Deliver a Complete Soil Analysis
Here it’s wise to pause before turning the underwear drawer into a laboratory instrument. The authors argue that their index offers an informative first glimpse of the biological dynamism and of certain fertility- and health-related characteristics. They do not claim that a buried garment alone diagnoses an entire ecosystem.
Caution matters because “soil health” encompasses many dimensions. The rate at which cellulose disappears lights up only part of that tapestry. Two patches can show similar degradation and still differ in other decisive properties. The tool is therefore framed as an initial guide, far from aiming to replace specialized techniques.
The numbers themselves set its scope. The statistical model used to explain the underwear index accounted for about 16.5 percent of its variation. There remained a lot conditioned by unrecorded factors, local peculiarities, and the inevitable heterogeneity of a citizen-science project conducted at hundreds of sites.
We can imagine the test as a thermometer facing a full medical checkup. The shreds tell a valuable story whenever we do not ask them to narrate the entire book.
The Real Brilliance May Lie Not in the Underwear
There were methods to study degradation long before this work. The authors explain that the drawback is that some techniques require careful handling, precise scales and, especially to involve the public, lack visual appeal. This detail may seem secondary, but it becomes crucial when citizens participate: gathering many sampling points requires non-specialists to want to collaborate and understand what they are observing.
A torn garment has exactly the opposite effect. Anyone can understand the contrast between freshly bought underwear and the hole-riddled mass recovered weeks later. Suddenly, the phenomenon gains an image. The work of a buried community stops being an abstract graph and appears before the eye as a fabric that is missing.
People’s response demonstrates the power of that idea. The initiative managed to gather information at hundreds of points that a small group of researchers would hardly have been able to cover with such breadth. And there lies another lesson: simplifying the entry door does not require compromising rigor. A playful idea can lead to serious questions, standardized measurements, and rigorous analyses.
The initiative managed to gather information at hundreds of points that a small group of researchers would hardly have been able to cover with such breadth.
Under Our Feet, Something Is Happening That We Rarely See
Let’s return to those two seemingly identical plots. Now we know that their outward similarity may conceal very different biological rhythms. Under the plants lies a network of organisms that processes waste, mobilizes nutrients, and participates in functions essential to ecosystems.
Soil is not a passive stage where life happens: it is an active agent in it. When a leaf falls, a root dies, or we add compost, a chain is set in motion linking tiny organisms to fertility, vegetation, and cycles with planetary reach.
The merit of the experiment isn’t simply discovering that cotton decomposes when buried. What matters is showing that this degradation, applied in a standardized way and cross-checked with other indicators, opens a simple window into processes that are difficult to trace directly.
That is why, 2,000 pairs of underwear change something more interesting than our notion of scientific instrumentation. They force us to look downward. What we usually call simply “soil” harbors dynamism, contrasts, and stories that are imperceptible from the surface. Perhaps that is the Swiss project’s most unexpected lesson: to make visible one of the planet’s most discreet ecosystems, sometimes all it takes is burying something you would never imagine as part of a scientific experiment.
