Ontario’s relatively youthful soils are less prone to micronutrient deficiencies, but there are situations where soil characteristics can lead to low levels of key micros in farm fields, says University of Guelph associate professor Dr. John Lauzon.
Speaking at the Ontario Soil and Crop Improvement Association’s MicroSmart Deep Dive meeting in Kingston, Ont., Lauzon noted that Ontario’s 15,000-year-old soil is a mere toddler compared to other areas around the globe where soil can be as old as one million years. That means some of the “deficiencies aren’t as pronounced as what we might see elsewhere, but we do see several, and the ones that we see most commonly here in Ontario are going to be zinc, manganese and boron.”
When it comes to deficiencies, Lauzon says pH levels can be a common denominator for all three micronutrients. “That’s because all three of those elements greatly increase in availability the more acid the soils become. And so if we’ve got high pH soils, which a lot of our soils in Ontario happen to be, then the possibility for deficiency is there.”
Ontario soils have formed over the last 15,000 years, but the story goes back much further. Lauzon notes that 400 to maybe 700 million years ago, Southern Ontario, due to continental drift, was physically at the equator under a shallow sea. “At that time, the coral that was growing in the area formed the basis of our bedrock — calcium carbonate, rich materials. After the last glaciation, that material was re-ground up and deposited to the soil surface, resulting in a pH that would have been at the time, 8.2 all the way to the top.”
In the last 15,000 years, the soil has reformed and some of those carbonates have weathered out of the top and started to move down through the profile, allowing the surface soil to start reducing in pH, says Lauzon. “But a lot of our soils still have a much higher pH than most areas of the world, and as such, even with relatively high availability of these micro elements, they may not be physically plant available because of that high pH.”
In this report, Lauzon tells Bernard Tobin that side banding zinc at the root zone is the best way for farmers to correct a zinc deficiency. When it come to manganese, foliar application would be the preferred option.
Overall, Lauzon says that while micronutrient deficiencies are common in Ontario, they are often mild and not a significant issue if symptoms are not visible. On-farm trials are recommended to identify specific needs and ensure effective use of micronutrient applications. Regular field scouting can help determine if micronutrient deficiencies are a consistent issue, warranting targeted applications.
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