Jake Erickson of the Dry Run Farmer-Led Watershed modeled the underwear before planting and after harvest. Despite hog manure and cover crops, the dry year and several tillage passes likely slowed the decomposition rate in the field. (All photos courtesy Tara Daun)

Across northwest Wisconsin, farmers in four local watershed councils volunteered to participate in a light-hearted competition aimed to turn some heads and crudely measure soil biological activity. 

The Soil Your Undies challenge is pretty simple: Bury a pair of underwear in the spring out in the field then let the soil microbes work on them for 50 to 60 days. The cotton in the underwear, being a natural fiber, is capable of quick decomposition in that time, but they need plenty of microbial activity to get broken down. Luckily, we’ve had a bountiful harvest of some super soiled Hanes. 

Between May 25^th and June 17, 30 pairs of underwear were planted across 4 counties. Those pairs were dug up between July 22^nd and August 3^rd. Field cropping history and tillage were all noted at time of planting. Unfortunately, a couple were lost; fields look awfully different after 60 growing days, and our markers were pretty difficult to find in 8’ corn. Picture me, crawling between corn rows on hands and knees looking for small pink flags and futilely checking out “before” pictures of the field to try and triangulate location. To my credit, and moreso the farmers’, we found almost all of them. 

More than one farmer called halfway through the challenge to say “we haven’t gotten any rain, that underwear is going to be as fresh as it was when we buried it.” Those farmers were all surprised at what their soil did even during a dry season. Moisture did matter a lot though. Dry fields without living roots in the ground decomposed less cotton as shown by the test plots at Mann Valley and Horse Creek. Whereas fields under irrigation, even with some tillage had shredded the whitey tighties.  

Each pair of briefs we dug up has told a really interesting story. In general, the fields that had a longer history of no-till and reduced tillage had better breakdown than those with more cultivation. For example, the River Falls FFA test plot has been no-tilled for 2 years whereas Tim Jennings’ field, less than a mile away has been no-tilled for 8 years. There was certainly a lot less of the underwear left in the 8 year field. Mike Wold, up in Dunn county has been mostly no-tilling on his fields for 20 years, and his pairs were some of the most degraded. A pair in Pierce County took the cake though. They were buried on a field that has been in CRP for most of the last 40 years. 

Another lesson: poop breaks down underwear faster. Sigh. The jokes just keep coming. But truly even with more tillage and less variety of crops in the rotation, farms with cow manure incorporation had a lot more breakdown. This wasn’t as true for incorporated turkey litter or even hog manure. A great comparison occurred at the Cormican farm in Glenwood City. Andy and Don planted underwear in two fields very close to each other. Both were no-tilled and both had cover crops last year, but in one field, their cattle had grazed off the covers and in the other, the covers were terminated chemically in the spring at two feet tall. The undies in the grazed field were a lot more deteriorated than in the field without livestock access. 

So some underwear broke down more, why does that matter? In short, healthy soil is more resilient to weather and can hold more nutrients than inert soil. How does that work? Mostly soil structure and water absorption. Organic matter, like roots and microbial colonies, create structure by literally gripping soil and absorbing water instead of allowing it to run over the surface. That makes healthy soil far less likely to erode during rains or blow away with the wind. Of course, holding onto that moisture is also gives crops a bigger moisture bank to draw from during drought.  Healthy soil microbes also unlock nutrients while breaking down organic matter, providing more fertility to crops. 

Is it as simple as it sounds? Of course not. Soil scientists note that biological breakdown can be slower in some very health soils because of a higher fungal activity. Soil fungus is great for soil structure and nutrient availability to plants, but it is a slow decomposer and takes more time than soil bacteria to break down material. Fortunately, more scientific measurements can provide a ratio of fungal vs. biological activity in the soil to folks who really want to get a better peak under their dirt. For the rest of us, we can use Hanes to get a general idea of how our soil is doing. One farmer who applied fungicide had a LOT of breakdown, and perhaps killing the fungus made more room for the bacterial colonies. Another who has been using lots of biologicals and had fantastic looking crops and extremely high biological measurements through testing had very little breakdown of the underwear. In short, burying underwear isn’t a perfect test of soil health. And this isn’t an exact science, but in general, it has shown general trends that more soil health practices are associated with more decomposition. 

Does more underwear breakdown translate to better crop yield? We don’t know yet. We’ll try to do some rough tracking at harvest time. But of course, yield is dependent on hundreds of different factors, especially rainfall. Does more corn mean less underwear? Like many of the underwear pulled up, the well of jokes on this subject is bottomless.

Tara Daun is the watershed coordinator for four Farmer-Led Watershed Councils in northwestern Wisconsin. More information on the project can be found at farmerledwatershed.org or by following @farmerledwatershed on Facebook. tdaun@wisconsinfarmersunion.com