Soil health scores spark interest

CARMAN, Man. — Most people like having statistics to measure things. Kids want to know how many goals they scored in a recreation soccer game, fans study Canadian Football League passing stats and parents scrutinize their children’s marks on a mid-term math test.

Similarly, most farmers aren’t satisfied with having healthy soil. They want statistics and data to measure the health of their soil.

“There’s a big movement switching toward this idea of having soil health scores,” said Marla Riekman, land management specialist with Manitoba Agriculture.

Riekman, who spoke at the Crop Diagnostic School in Carman, Man., July 6, said universities and companies have developed testing methods to estimate the health of soils.

Cornell University, for example, has a testing protocol to evaluate characteristics like soil tilth, soil drainage, the number of beneficial organisms, aggregate stability and the population of plant pathogens. The Cornell system uses all that information and generates a soil health score.

Marla Riekman, a Manitoba Agriculture soil specialist, says growers should touch and smell soil to get a sense of healthy and unhealthy soils. Riekman discussed the value of examining soil, close up, at the Crop Diagnostic School in Carman, Man., July 6. | Robert Arnason photo

Marla Riekman, a Manitoba Agriculture soil specialist, says growers should touch and smell soil to get a sense of healthy and unhealthy soils. Riekman discussed the value of examining soil, close up, at the Crop Diagnostic School in Carman, Man., July 6. | Robert Arnason photo

Riekman said the Cornell approach is fine, but the system was designed for soils in the northeastern U.S., not the Prairies. And a score means little if a farmer can’t compare it to another number.

“If I was doing some kind of general soil health test and came back with a score of 60, is passing 50? Is passing 70?… That’s the kind of thing we don’t know,” she said.

“Unless everyone (other farmers) around me also had a score, I have no way of knowing whether (the number) is good, bad or average.”

The Cornell method is complex and a number of western Canadian growers have adopted a simpler method to assess soil health: the Solvita test.

It measures the amount of carbon dioxide a soil sample releases. A high level of carbon dioxide indicates the soil has a healthy community of micro-organisms.

To explain the Solvita test, Riekman held up a glass jar of soil and a chart with colours ranging from blue, green to gold.

A sample of soil goes into the jar along with a small paddle that changes colour as carbon dioxide is released.

The paddle is removed after 24 hours and its colour is compared to the colours on the chart.

“This (colour) is an indication of how much CO2 has been gassed off by the microbes in the soil,” Riekman said. “You can take this coloured number … and calculate how many pounds per acre of CO2 has been gassed off.”

The test is interesting but western Canadian producers need to know how their Solvita result compares to farms with similar soils and production practices, said John Heard, Manitoba Agriculture soil fertility specialist.

“If I’m getting rapid microbial breakdown, that would suggest I’m getting more in-season nitrogen being released,” Heard said. “This procedure is… being used around the world (but) it’s just really lacking right now in calibration.”

Riekman agreed, adding many more tests will be needed before prairie producers can make sense of their Solvita result.

“What we would have to do is (conduct) this soil test in many different soil types, many different cropping systems and many different climatic environments.”

Although data and scoring is useful, Riekman said evaluating soil health is also an art.

To illustrate that point, she displayed several core samples of soil at the Crop Diagnostic School. Riekman encouraged participants, mostly agronomists, to touch the soil and use all their senses, including smell, to assess the condition of the soil sample.

Riekman also promoted the idea of digging soil pits, where producers or agronomists get in the hole and take a close-up look at the soil.

“There is value to digging a hole. We’re not going to know a lot about soil just looking at the surface.”

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