Soil health under the microscope



IT’S NO SECRET much more is known about what happens above ground than below the soil surface in agriculture. Now renewed focus on soil health research in Ontario could evolve to impact farming practices forever.

In the United States, indicator tests are being developed to help farmers link management practices to soil health improvements. Soil specialists in Canada are keen to find out if these could be of any benefit here and define exactly what determines what a healthy soil is, once and for all.

Both Dr. Laura Van Eerd, of the University of Guelph’s Ridgetown Campus, and Dr. Amanda Diochon, based at Lakehead University, are two researchers pursuing answers to this question in the coming year. They agree there’s much more to declaring healthy soils than just noting soil organic matter content increases.

“Soil health is like our health,” Diochon explains, “you can’t just measure one thing and get a good indicator of what soil health is”. Think of it like blood pressure. Having a normal blood pressure reading is great, but does it mean you’re perfectly healthy? Not necessarily.

Van Eerd says that without standards like the ones being developed in the U.S., many farmers can only point to organic matter levels as evidence of superior farming habits. She distinctly recalls being put on the spot at a dinner party, asked to verify if a farmer at the table truly was experiencing organic matter increases because he was using no-till and cover crops. Instead, she asked the farmer if it was only changes in organic matter he’d observed since changing his farm practices.

“He said he was pulling bigger equipment with the same horsepower, saw less ponding, and got 60 bushel beans in the previous dry year,” Van Eerd recalls. “It’s those things, in my mind, that are an indication of soil health.”

Van Eerd has already assessed one indicator developed in the U.S. called the Cornell Soil Health Test. Although it didn’t prove equally effective in Ontario, it was able to show rotations which include winter wheat and alfalfa or red clover contribute to very healthy soils. She’s now moved on to evaluating the Agricultural Research Services Soil Test by Dr. Rick Haney, to see if it performs any better.

The Haney test was developed on rangeland, and it’s based on parameters that are new to soil science. “What we want to know is if the Haney will be able to detect differences in production systems,” Van Eerd explains. “If we’re going to pick one, then I want one that’s going to be sensitive to management and is going to be useful.”

Meanwhile, Diochon will turn her eye on the characteristics of soil organic matter to assess whether it could offer more specific parameters to soil health evaluations. Unlike total soil organic matter alone, she explains that several attributes of soil organic matter are highly responsive to changes in management practices like tillage and crop rotation practices. “Soil organic matter is the heart of the soil,” she says, “It’s a source of nutrients, it holds water, it builds resilient soils, and it’s the largest terrestrial reservoir of carbon.”

By comparing attributes such as total organic carbon and mineralization, she hopes to connect soil organic matter to the more resilient soils farmers regularly report. “By identifying responsive attributes of soil organic matter, we could incorporate those into a soil health test for Ontario,” she says.

Although some farmers may question the value of expanding on current soil testing abilities in Ontario when they can gauge the relative health simply by observing the growth of crops, Van Eerd asserts that there are other reasons than production to establish a new standard.

“It’s possible that we’re going towards a carbon trading system so we need to know where agriculture stands and we need to provide numbers,” Van Eerd says. “By measuring soil organic matter, maybe it will identify practices that sequester more carbon than others.”

Identifying the differences between the effects of farm practices and the impact of changing environments on soil characteristics now could ultimately prove extremely valuable in the future. Both Van Eerd and Diochon are collecting their samples from long-term trials at experimental sites in Ridgetown and Elora to capture some environmental differences and still avoid any year to year variability produced by management changes. Dr. Josh Cowan, manager, research and innovation with Grain Farmers of Ontario, says this was a very appealing component in the design of both experiments.

“We already have the long term trials and we know the history of these plots,” he says. “These projects evaluate the current status of soils we know are more resilient in terms of yield.”

Cowan says farmers already have a good understanding of things that tend to be good for soils but quantifying these observations remains a challenge. Establishing an appropriate soil health indicator isn’t going to impact production knowledge gaps drastically, but having an indicator is the first step to evaluating production practices in terms of their impact on soil health. When things like soil organic matter change so slowly in relation to rapidly evolving farm management technology, it simply isn’t good enough to wait ten years before seeing the impact of any significant change he says.

“Farmers want to do a good job taking care of their soil so how do we best help them do that?” he asks. “This is one of those ways that we can hopefully quantify the status of the soil better and if it can help you get a more resilient cropping system, everyone wins on that.” •