Digging into our knowledge of the living soil

Soil testing for the microbiome is not yet standardized, but DNA sequencing has allowed for soil scientists to determine proxy measurements

By Jackie Clark
Staff Writer
Better Farming

Farmers and researchers are starting to develop a better understanding of the importance of a well-functioning cooperative community of micro-organisms, called the soil microbiome. To help improve their soils, producers must have an accessible way to evaluate the microbiological activity in their fields.

“Soil testing is an absolute first step,” Don McCabe tells Better Farming. He’s a farmer in Lambton County, vice-chair of Biological Carbon Canada and former president of the Ontario Federation of Agriculture.

However, “there’s (currently) nothing that’s absolutely standardized or approved,” to evaluate microbiological activity, he says.

Some hope exists in using other soil measurements as proxies for biological activity.

“DNA and RNA sequencing are at the cusp of helping farmers with their management,” Dr. Sarah Hargreaves says. She is a farmer and director of research at Ecological Farmers of Ontario. Hargreaves has a PhD in soil microbial ecology.

However, “the interpretation of that data can be mind-blowingly difficult,” she says.

Thankfully, sequencing has allowed labs to find other measurements that correlate with positive microbial activity.

soil sample bag

An example would be the soil health test developed by A&L Canada Laboratories Inc.

“We have developed a soil health test that looks at 487 different parameters in an algorithm that correlates very strongly to what we call soil health,” Greg Patterson, founder and CEO of the company, tells Better Farming.

Bacteria and fungi measurements are still time- and cost-prohibitive for most producers, he explains. So, the company uses biological assays (testing procedures) to build the algorithm that connects nutrient levels to biological activity.

“We know, based on certain levels of certain nutrients, that we’re stimulating certain organisms,” he says.

From this soil health test, A&L Canada Laboratories generates a “report for farmers to use as a guide,” Patterson says. Then, farmers can apply nutrients to adjust the microbial activity in their soils.

These proxy measurements for microbiological activity are positive steps toward farmers having the ability to monitor and support their soil’s microbiome.

A one-time test is not enough, however.

Farmers must use representative sampling protocols and take samples over time, McCabe says. “You might not be able to measure a difference just in one year.”

He also advocates for updated comprehensive soil mapping in Ontario to help producers better understand what they have to work with.

“It’s truly a competitive disadvantage that we do not have soil data available to farmers in Ontario. It’s a base resource, a base fact that society should know,” he says.

For the future of soil microbiome testing specifically, Hargreaves says that “a test of the microbiome that focuses on the functional groups of microbes,” would be most useful. That way, farmers could understand what the microbiome is doing for their soil. BF

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