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What do a farmer in Scotland, a soil systems biology professor in Australia, and citizen scientists across Switzerland have in common? Over the past few years, they’ve all been burying pairs of cotton underwear in fields and garden beds. After a few months, they dig them up to check their condition. Brown stains are a bonus. The more holes, the better. Believe it or not, but it’s one of the best DIY tests to check the health of your soil.
Healthy soil boasts many microorganisms, optimal water, and abundant living roots that work together to break down cotton undies quickly. If, after a few months in the soil, the underwear all but disappears. If you find your underwear intact, you have some work to do on your soil health. But why underwear? Simply for the fun of it! In fact, you can use any piece of textile, so long as it’s 100% cotton. “The lifeforms in the soil should begin eating the cellulose sugar, from which cotton is made, and start decomposing the organic material,” a 2024 article in The Scottish Farmer states.
Get started by digging a hole
If you want to try this at home, you need an appropriate pair of underwear. If you don’t have an old pair at home or aren’t sure whether what you have is made of pure cotton or a cotton blend, you’ll need to borrow or buy a pair — or forgo the undies for another cotton item. A pack of 10 white Fruit of the Loom women’s cotton briefs is just $19.90 on Amazon, or Walmart has a 4-pack of men’s 100% cotton boxer briefs for $42.99. You’ll also need a spade and some small flags or other markers.
Tighty-whiteys in hand, choose a spot you want to test (or spots if you’re testing multiple fields or garden beds). Dig a hole about three inches deep. Place the cotton underwear into the hole and take a photo to refer to later. Fill in the hole with the soil you removed, and mark the spot with your flag so you can easily find it again. To get the best results, you need to wait at least 60 days before digging the underwear up again. Aim to bury your briefs in June when soil microbes are typically most active. This method works whether you’re an American farmer with acres of orchard or a passionate backyard gardener with a single vegetable patch living in New Zealand.
Analyze the results
Analyzing the results of this experiment is straightforward. Gardeners left with underwear they could still put on can start improving their soil in a few ways: add more organic matter into your soil to encourage microbial activity, lean into the no-dig method, plant cover crops like legumes, adjust the moisture content, and reduce pesticide use. “We are learning that it’s the microbes, the bacteria, the fungus, the predators that drive the whole nutrient cycle in our soils that feed the crops,” Pennsylvania soil health coordinator Lisa Blazure told the Chesapeake Bay Foundation in 2024. In other words, with a little TLC, the poor soil in your garden can be revitalized.
Curious how your results compare to others? There are interactive online maps you can take a look at to see how your soil health compares with that of others. UK residents can take a look at the Plant Your Pants map, the Soil Your Undies map records findings of Australian gardeners and farmers, and those in Switzerland and other parts of Europe can view the Projekt Beweisstück Unterhose (Proof by Underpants) map.
