How active is your soil? Try the underwear test!

by Contributor:  Claire Coombs¹, Ridgetown Campus, University of Guelph

Soiled underwear has taken on a whole new meaning in my world, where the dirty and decrepit reign. In June, I planted something in the ground that I had never even considered burying, 7 pairs of men’s cotton briefs.

Soil biology can be a difficult concept to study, measure and teach. There are several tools and methods that can be used to measure soil biology, however these do not generally provide interesting or engaging, extension material. All this changed, when myself, and soil management specialist, Anne Verhallen, heard a presentation at a Midwest Cover Crop Council meeting. Using the cotton test, a soil biology measure using cotton swatches, as a basis, this researcher placed men’s 100% cotton briefs in the soil and removed after a set period of time to measure biological activity. The cotton test uses pre-measured squares of cotton as “food” for soil organisms. In soils with higher biological activity, there would be less cotton remaining when the squares are removed.  While this can be an excellent tool for displaying biological activity across differently managed fields, it remains a little dull. However, replace cotton squares, with cotton briefs and you have everyone’s attention, including mine.

Figure 1: Burying a test pair of the cotton briefs in Ridgetown

On June 10, 2015 I buried 4 pairs of brand new, washed men’s small 100% cotton briefs (except for that waistband) in the long term rotation/tillage plots on Ridgetown Campus, Figure 1. I also cut a pair in half and buried each half at the front of the trial so we could dig up “test” pairs to determine how long to the leave the underwear in the ground. Each pair was buried in a soybean plot deep enough to be fully covered by soil, but with the waistband sticking out of the ground so the underwear could be easily extracted. The underwear was then left for two months without disturbance and then I dug them up, or what was left of them! As seen in image 2, there were noticeable differences between the four pairs, depending on where they had been buried. The less underwear left is an indication of increased biological activity.

Figure 2: From left to right, cotton briefs dug up after 2 months of being buried in a) No-till corn-soybean-wheat+red clover rotation, b) no-till soybean, c) conventional till corn/soybean rotation and d) conventional till continuous soybean

Now if you are paying attention, you will know that I said I buried 7 pairs of underwear. So far, I have mentioned my test pair and four across the rotation/tillage plots. The last two pairs went on a road trip with me to Merlin, ON where a farmer in the area, Blake Vince, was more than eager and willing to have underwear buried in his field.

A pair was buried in his field which has been no-till for 30+ years and has an excellent rotation with extensive cover crop usage. The other pair was buried across the road in a conventionally tilled field with no cover crops. We again left the two pairs alone for two months and returned to dig them up.

From Figure 3 it is easy to see that most of the cotton from Blake’s field was gone, which can lead to the assumption that there is increased biological activity in this field as compared to the conventionally tilled field.  You can also see Blake and I digging up the underwear on Youtube at https://www.youtube.com/watch?v=GRRkOlSJcK8,  Soil Biology “The Cotton Test” Ontario Canada and https://www.youtube.com/watch?v=QBwMLXHBMOY Soil Biology “The Cotton Test” Ontario Canada Video 2.

Figure 3: Briefs removed from a conventionally tilled field (left) and Blake Vince’s well managed field (right)

Both in Ridgetown and Merlin, the underwear we were left with ranged from being fairly intact and wearable, to almost non-existent. While this test is probably never going to be used in scientific literature as an accurate way to measure soil biological activity, though I would love to see a scientific article with the work underwear in it, it does provide extension specialists with an exciting, eye-catching and engaging way to demonstrate soil health and biology.

¹ Claire Coombs is a research technician at Ridgetown Campus, University of Guelph and is currently assisting the OMAFRA Soil Program.