By Sandra Caswell, Master Gardener In Training
Bet that title got your attention!
In her last blog, MJ talked about “Garden Maintenance Tasks for September and October.” I’m going to pick up on that theme with another important fall task: building your soil—and, as you’ll soon see, that’s where underwear comes in.
Microbial activity is key to a healthy garden. Microbes include worms, insects, spiders, and all sorts of other creepy crawlies that call your soil home. Think of them as your garden’s best friends.
One of their most important jobs is aerating the soil. This helps water penetrate deeply and gives plant roots room to spread out and down in search of nutrients. Strong roots below mean strong, healthy plants above.
Fall is a great time to support your soil’s microbial community. After removing spent annuals, spread 2–3 inches of organic matter—such as compost, manure, or worm castings—over the soil. The goal is to disturb microbial life as little as possible. Instead of tilling the compost in, simply leave it on top and let the microbes munch away all winter, gradually working it into the soil for you.
That’s what I do with two of my raised vegetable beds. In the other two, I plant a cover crop, typically winter rye. It acts as a “green manure,” helping improve soil nutrients, including nitrogen and potassium. I scatter the winter rye seed, lightly rake it in, and water it for a few days until it sprouts.
Next spring, I’ll turn the rye into the beds and let it decompose for about a month before planting. Voilà—organically recharged soil! The microbes will be happy, and so will next year’s vegetables.
So, What’s This Got to Do With Burying Your Undies?
Every April, the Soil Conservation Council of Canada encourages farmers, gardeners, and backyard scientists to try a surprisingly entertaining test of soil health: bury your underwear.
The idea is simple. Bury a pair of 100% cotton underwear in your garden and dig it up a few months later. The faster the cotton decomposes, the more microbial activity is happening in your soil.
It may sound like a joke—and, admittedly, your neighbours may have questions—but the science behind it is legitimate.
Scientists at Switzerland’s Agroscope and the University of Zurich took the idea to a whole new level, leading a thousand citizen scientists in burying underwear in gardens, fields, and meadows. After two months, the participants dug up the undies and dried them for analysis.
And what did they find? Microbial activity tended to be higher in private gardens, where gardeners regularly added organic matter and paid attention to moisture and irrigation. The underwear buried in those gardens showed the greatest degree of decomposition. Grasslands showed the least microbial activity, while arable farmland fell somewhere in between.
In other words, the more thoroughly your garden destroys a pair of cotton underpants, the more lively things may be happening beneath the surface.
So, if you thought your garden tasks were finished for the season and it’s time to hang up your rake, think again. Even if you have no intention of participating in the underwear challenge next spring, set your garden up for success by simply giving your soil a good helping of organic matter this fall. You’ll be feeding those hard-working microbes and setting your garden up for healthier soil next spring. Your plants will thank you. Your microbes will thank you. And your underwear? Well, let’s just say it may have served an important scientific purpose.
Please see links below for more information about the Soil Your Undies challenge or the Swiss study. Also listen to the last 15 minutes of the September 18th podcast of CBC’s Quirks and Quarks for a discussion with the lead scientist at the University of Zurich.
