LETHBRIDGE – Farmers have been telling plants’ fortunes for thousands of years by reading their leaves. Electronic tools are building on that experience and a new one is now being tested in Western Canada.
Called Dualex and made by the French manufacturer Force A, it adds to two others, the Green Seeker and SPAD meter, both of which measure the chlorophyll in plant leaves relative to the rest of the leaf’s composition. The Green Seeker uses near infrared reflection for its baseline while the SPAD relies on a strong light emitting diode.
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These tools use sensors to read the two types of light to which leaves are exposed: one that provides baseline information on the leaf’s density and other characteristics and the other that measures specific chemicals in the leaf, recognizing their colour.
The greater the amount of colour, the better or worse off the plant is, depending on the chemicals or compounds analyzed and the maturity of the plant. The tools are used to measure nutrient and water shortages and insect and disease stress before the human eye would be able to interpret the problem.
The Dualex uses fluorescence to read polyphenols in the leaves, which are created when plants are under stress.
“So far we’re finding the Dualex is the most sensitive,” said Anne Smith of Agriculture Canada, who is testing it.
The Dualex costs $12,000, compared to $2,000 SPAD meters and the $5,000 Green Seeker.
“It doesn’t matter which one you rely on, none of them are good in isolation. That’s why we test them to find out what they can do, both for researchers and for producers,” she told about 300 producers attending the Southern Applied Research Association’s Diagnostic Field School held July 10-12 in Lethbridge.
“We don’t have any (calibration) curves for this thing yet, but it’s coming.”
To be of use to producers the tools need to be able to identify stress at a time when producers can economically respond to problems.
The other two meters are being used in high value crops such as potatoes and corn. Small grains producers use the Green Seeker to evaluate crops on the fly during other applications, but so far researchers say the technology is still being refined to deliver benefits to a wide range of growers.
“Right now, these tools tell you there is a problem,” Smith said.
“They don’t know which problem, but it can tell you that it’s time to investigate before your eyes will.”
Researchers say producers who use these meters must make sure they take consistent readings and collect multiple samples to ensure a trend throughout a population of plants.
“Ideally, I think the right tool of the future might be one that combines the sensors of all of these devices – measure chlorophyll and polyphenols,” she said. “Then we might have a machine that will really read the leaves.”
