Regenerative agriculture had a big year in 2020.
It received a tremendous amount of media attention and Cargill committed to increase regenerative ag practices to 10 million acres of North American farmland by 2030.
But more attention usually means more scrutiny.
Some scientists are now questioning the hype around regenerative agriculture, particularly the concept that activating soil biology, with practices like cover crops, intercropping and reduced tillage, allows a farmer to cut fertilizer rates.
Andrew McGuire, a soil scientist at Washington State University, thinks producers are jumping to the wrong conclusion.
There’s another reason why a regenerative farm requires fewer nutrients: it produces less grain and oilseeds than a conventional farm.
“Yes, regenerative agriculture does reduce inputs, but the primary mechanism by which it does this is the reduction of nutrient exports from the field,” McGuire wrote in a blog.
“There’s less production per acre, over the whole cycle, and that part isn’t discussed very often,” he added in a phone interview. “But if you pointed it out to a lot of researchers they’d say, yeah, of course.”
Proponents of regenerative ag frequently say that boosting soil biology is key to a production system that requires less fertilizer.
McGuire said changes to soil biology can improve nutrient cycling and “tighten up” the system. But it only makes a small difference.
The free-living bacteria in the soil, which transform nitrogen gas in the atmosphere into nitrogen compounds that a plant can use, are not the same as synthetic fertilizer.
“I think they (regenerative advocates) are attributing it to the wrong thing,” said McGuire, who frequently uses Twitter to challenge assumptions in regenerative agriculture.
“If you look at the rates you’re getting from mycorrhizae, or other more active soil biology, the rates are very, very low compared to what we need for modern agriculture.”
They possibly provide 20 to 30 pounds of nitrogen per acre, McGuire said, not nearly enough for high-yielding crops.
“It’s not going to supply a corn crop, for instance. It could supply a pasture but it’s not going to supply your annual crops at the yields we’ve come to expect.”
Ryan Boyd, who farms north of Brandon, is well known in Manitoba as a leader in the regenerative movement. He operates a mixed farm with his wife and parents, where they raise cattle under intense grazing management, use corn grazing, intercrop pea-canola and are no-till farmers.
On his farm, he does export fewer nutrients than his conventional neighbours.
“If you have livestock you’re not exporting as much, so you don’t need to access as many nutrients,” said Boyd, who received a prestigious Nuffield scholarship in 2019 to study grazing ruminants.
“Have I been able to maintain yields and produce as prolific (a crop) if I had used a lot of fertilizer, comparable to my neighbours? I’d say we haven’t. We’re not there.”
However, the biology of soil remains a mystery.
There can be billions of bacteria and fungi in a gram of soil and scientists understand only a fraction of the biological processes within the soil.
So, it may be possible to feed the soil biology and create a system where a producer can apply fewer nutrients and achieve robust crop yields.
“I think it can be done, but I’m certainly nowhere near yet,” Boyd said. “What it all boils down to (is) the microbial activity that is mediating the nutrient transfer to the plants and mineralizing some of the stuff that would be otherwise unavailable.”
That said, Boyd acknowledged that low-input or no-inputs has become a mantra for some regenerative farmers, including himself.
Fertilizer is a way to “kick start” the system and applying nitrogen when canola is $13 a bushel makes economic sense.
“I wouldn’t jump to the conclusion that regenerative has to be low input,” Boyd said. “I think that’s where I’ve gotten stuck in a rut on our farm the last few years, is not allowing myself to use some inputs when it would’ve been a high marginal return…. Regenerative isn’t practices. It isn’t cover crops, it isn’t mob grazing, it’s not intercropping. Regenerative is an outcome and how we get there doesn’t matter.”
That outcome, or objective, likely varies from farm to farm.
But most producers want their farm to be profitable and resilient to adverse conditions when commodity prices are down or if there’s 20 millimetres of rain in July and August.
Spending less on crop inputs is one way to mitigate risk.
“In some cases, it’s going to make more sense to reduce yields and reduce inputs and go the regenerative way,” McGuire said.
“Their first priority is to stay in business, not to feed the world.”