By Connor Lynch
KINBURN — Eastern Ontario has a “hidden hunger” eating away at its soybean crops. Last year the fields were spared but it’s a problem that’s not going away.
The hidden hunger is a chronic potash deficiency in soils that make the plants vulnerable to white mould and could be costing producers as much as eight bushels/acre in soybean yields, said independent agronomist Paul Sullivan, based at Kinburn, west of urban Ottawa.
Last year largely spared Eastern Ontario; there were only occasional, scattered pockets of the mould. But that was thanks to the largely warm and dry weather, Sullivan said. Weather is at best an unpredictable ally, and even in a year like that some producers could lose as much as 10 bu/ac in yields, he said.
“Traditionally, (white mould) is our most serious soybean disease. It’ll be back next year.”
It was a nightmare back in 2013 and 2014, Sullivan said, with some producers losing as much as half their soybean yields. White mould tends to hit hardest if it can get started in July, when soybeans are typically flowering.
But lots of factors go into it. Taller soybeans tend to be more vulnerable since they tend to lean into each other; tillage also tends to mean you’ll have more problems with the disease.
The irony of white mould is that it’s a high-yield problem. Since it’s growing off the plant, the better the soybeans are doing, the more food for white mould. Row width has been touted as a method to reduce white mould. That’s true, said Sullivan, but only so much as it also reduces yields.
Potash deficiency is one of the major stressors on Eastern Ontario soybeans. A soil test is the sure-fire way to know how much you have; Sullivan recommends at least 120 ppm. Crop rotation also helps. The more regularly you plant soybeans in a given field, the higher the risk for white mould, he said.
Fungicides are useful preventatively. “Other factors create yield; fungicide protects it. If you get white mould in a crop, it spreads kind of like a forest fire.”
You can keep a lid on white mould “if you’re proactive on managing for it, it really can be held back.”
