For University of Minnesota plant pathologist Linda Kinkel, some of agriculture’s most promising solutions for farmers begin with what’s happening beneath the soil surface.
For nearly four decades, Kinkel has studied how microbes interact with plants, including how certain soil microorganisms can suppress disease, support plant growth and help crops withstand environmental stress. Her research also offers insight into the growing interest in biologicals and biostimulants as farmers look for ways to manage input costs and improve crop performance.
“And more specifically, I’ve spent all those decades of work really trying to understand where and why and how microbes can help plants grow better, be healthier, produce yields, despite all the complicated things that the weather and the world can throw at them,” Kinkel says.
A Potato Field Mystery Leads to a Deeper Understanding of Soil Microbes
Kinkel’s research program at the University of Minnesota began with a mystery involving the university’s potato breeding nursery.
In the 1970s, plant diseases were common in the nursery, where researchers evaluated potato varieties to identify those that could withstand disease and advance in breeding programs. But over the following two decades, the diseases began disappearing.
Researchers tried to bring the disease pressure back, including adding pathogens to the fields, but nothing worked. Eventually, they had to abandon the field for potato breeding.
In the early 1990s, a faculty member approached Kinkel to investigate what had happened.
“So they tried to make disease worse in those fields. And finally... Everything they did to try to make disease worse, adding pathogens to the field, nothing worked and they had to abandon that field for the potato breeding nursery,” Kinkel says. “So this faculty member, that was the mid-1970s, this faculty member wondered what had happened. So in the early 90s he came to me and he said, I want to figure out what happened.”
Kinkel began studying the soil and its microbial community to understand why the pathogens could no longer establish themselves as they once had.
Her research pointed to the collective activity of the microbes already living in the soil.
“It’s not one magic microbe that is, you know, magically doing all these wonderful things for plants,” Kinkel says. “It’s combinations of microbes that work together in important ways together with one another and with the plant to support crop productivity.”
That distinction is important as researchers and companies develop microbial products for agricultural use. The benefits of a soil microbiome may depend less on one microorganism acting alone and more on how an entire community functions together.
How Microbes Can Help Plants Fight Disease
Kinkel says microbes can suppress plant pathogens in several ways.
Some directly inhibit or kill pathogens. Others physically prevent pathogens from reaching plant roots, where infections can begin. Microbes can also activate a plant’s own resistance mechanisms, helping it defend itself against disease.
In other cases, microbes may help plants grow more vigorously, allowing them to better withstand disease pressure.
“But there’s one other thing that’s not actually directly plant suppression, but it helps plants deal with disease, which is to say microbes can make roots and foliage grow more vigorously, and sometimes you can simply outgrow a pathogen,” Kinkel says.
The challenge is that these functions depend on the broader microbial community and the conditions in which the organisms are living.
That complexity also helps explain why adding a beneficial microbe to the soil does not guarantee a consistent result.
Why Microbial Products Don’t Always Deliver Consistent Results
For farmers considering biologicals, the biology already present in the soil matters.
A microorganism applied through a commercial product must establish itself and function within an existing community that may contain billions of other microbes. Whether it delivers the intended benefit depends partly on the organisms surrounding it and how they interact.
“One magic microbe isn’t good enough,” Kinkel says. “It has to be a microbe that can live within that soil community, and critically has to function within that community.”
She compares microbial behavior to how people may act differently depending on the company they keep.
“Just like when my kids were younger, how they behaved depended upon which friends they were hanging out with. Microbes are exactly the same,” Kinkel says.
A microbe’s ability to perform a function, such as fixing nitrogen, solubilizing phosphorus or suppressing a plant pathogen, depends on its partners and whether it can operate effectively within that environment.
For biological products to gain greater traction with farmers, Kinkel says the industry must demonstrate reliable performance in the field.
“Effectiveness and consistency. We really need, as an industry and as the academic researchers, we need to deliver for growers what growers deserve,” she says. “They deserve products that they can use reliably and that provide a significant return on investment. And in the absence of that, we won’t get more traction.”
Do Biologicals Really Offer New Opportunities for Farmers?
Despite the challenges, Kinkel sees significant potential in the next generation of biologicals and biostimulants.
“I’ve been doing this decades. I see more promise in the industry today than ever before,” Kinkel says. “And I also see adoption rates climbing dramatically over the last decade.”
She expects the sector to continue growing, particularly as research advances and companies develop products with more targeted capabilities.
For farmers evaluating biological products, she says the value proposition does not have to depend entirely on increasing yields. A product that delivers comparable performance to an existing input at a lower cost could also provide an economic benefit.
Kinkel says some microbial products on the market can match the yield benefits associated with fungicides.
“And when you have a biological that can match the yield benefit from a fungicide at a fraction of the cost, you might not be getting more yield, but you’re saving money,” she says.
She points to three ways biologicals could provide value: reducing input costs, saving on inputs and enhancing yields.
The challenge for farmers is determining whether a particular product can deliver those benefits under their own growing conditions. Kinkel says continued research and data demonstrating product performance will be essential to guiding those decisions.
‘These Are Not Your Grandpa’s Biologicals’
Kinkel acknowledges that biological products have not always lived up to expectations. But she cautions against judging today’s products solely on the performance of earlier generations.
“These are not your grandpa’s biologicals,” Kinkel says. “The biologicals products, the microbial products on the market today are a completely different suite of capabilities than were available to growers 10 years ago, and it will only get better.”
She says the industry should continue demanding data to validate product claims and help farmers make informed decisions. At the same time, she believes advances in microbial technology warrant a closer look at what newer products can offer.
“I think that the industry is right to continue to demand the data that validate or that can guide good decision making, but don’t assume that it’s snake oil because the industry has moved beyond that,” Kinkel says.
For farmers weighing whether biologicals belong in their crop management programs, Kinkel’s research underscores a central point: Microbes are not a magic bullet, and their effectiveness depends on more than the organism listed on a product label.
Understanding how those microbes interact with the soil, the crop and one another could help researchers develop more reliable products — and help farmers determine where biologicals can deliver measurable value.
