Soil microbial health with professor Dave Hume
Is your underwear being eaten? Some progressive farmers are hoping so. Soil microbial health is a common concern for farmers, especially in the younger generation, and eaten underwear is a sign of good soil health.
“There’s a growing increase in ‘I wonder if’ in young farmers,” says Dr. Dave Hume, professor emeritus with the U of G. “The young farmers are more receptive to the idea of soil health.”
Hume is a soft-spoken, bespectacled man who sits comfortably in his well-lit office at the University of Guelph. Despite his retirement, Hume is often found in the Crop Science Building in his blue jeans and work boots running some of his own experiments on the efficacy of soybean inoculants or offering advice to graduate students.
Hume explains that the younger generation of farmers has had greater exposure to the idea of soil health, and it’s working. According to Hume, younger farmers are more likely to change their management strategies to improve soil microbial health.
Millennial farmers are thinking about the health of the farmland they are inheriting more than their parents did. As higher education in agriculture becomes more commonplace and public knowledge surrounding environmental issues grows, soil microbial health is coming into the spotlight.
In July 2017, farmers from the Soil Conservation Council of Canada decided to start testing their soil health with underwear. White cotton underwear was buried in the field at the start of the growing season. At the end of the summer, the farmers dug up and examined them. The farmers discovered that the cotton briefs had been consumed by the soil bacteria to varying degrees. The level of decomposition of the underwear should give farmers some insight into the rate of microbial activity in their soil.
So how does it work? Manitoban soil specialist, Marla Riekman, explains that soil microbes are just as happy to eat up cotton underwear as they are to eat crop residue in the soil. Both crop residue and cotton underwear are sources of carbon and microbes are not picky. In more microbially-active soils, the underwear will be further decomposed. In less active soils, the underwear will remain intact.
Claire Coombs, a research technician at Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), performed the “underwear test” a few years ago. The plots included some long-term no-till and conventional-tillage soybean test plots grown in a corn-soybean rotation. These were compared to soybeans grown in a three-year rotation with corn and wheat. She found that the no-till plots in the wheat-corn-soybean rotation were the most microbially active.
No-till agriculture is a farming technique in which crops are grown year after year without disturbing the soil through tillage. Benefits include better water retention and improved soil structure.
Coombs’ conclusion might not come as a surprise, as no-till management is a rising trend in Ontario agriculture. Not only does no-till reduce labour, but evidence of soil health benefits seems to be growing.
Coombs encourages farmers to bury some cotton underwear in their own fields. She wants farmers to gain additional perspectives on the health and activity of their soils. The “underwear test” offers a good visual to which farmers can refer. If conventional farmers are finding poor activity levels in their soil, no-till may be a better option to consider.
Hume is also a supporter of no-till cropping practices. He argues that no-till is the most economical way for farmers to improve soil health and soil structure. It improves soil activity and microbial health by allowing colonies of microbes, earthworms, and other soil dwellers to grow and thrive over time.
Hume says that caring for soil microbial health, whether through no-till or not, is just one part of an important and complex system. Focusing on soil health alone is not necessarily going to get you the bin-buster yields you desire.
“Cover crops [are] also a part of soil health,” he says. “Don’t leave bare soil, so root exudates are available to the soil organisms as much of the year as possible.”
Hume also says that fertility and soil microbial health go hand-in-hand. Increased yields rely on both factors. It is unclear as to whether good fertility is a result of or cause of good soil health.
“You don’t know if that’s the chicken or the egg,” Hume points out. Regardless of the order of improvement, Hume agrees that soil microbial health is a valid concern for young farmers.
According to the Iowa State University Extension and Outreach website, healthy soils are less prone to erosion and tend to have higher aggregate stability. Crops grown in healthier soils tend to withstand drought and big rainfall events better than soils with poor health. Ontario farmers have noted signs of climate change in recent years including more variable weather conditions. Improving soil health is one way to hedge against extremes in climate.
Over these long winter months, farmers might even consider purchasing a package of white cotton briefs of their own to plant with the soybeans and corn in the spring.
Featured image by Paige Kennedy