Summer has officially arrived, and it’s time to get out and assess soybean plant stands.

In this episode of RealAgriculture’s Soybean School, we catch up with Ontario Ministry of Agriculture, Food and Rural Affairs soybean specialist Horst Bohner as he surveys plots at a research site in Bornholm, Ontario.

As Bohner surveys a stand planted on May 8, he discusses how growers can do a quick assessment of yield potential. “Ideally, we would want five or six trifoliates before they start to flower for maximum yield potential,” he says. “It’s really hard to catch up if you don’t have those trifoliates before they start to flower.”

Canopy development is another factor growers can use to measure their crop: “Ideally by the beginning of July we want that canopy completely closed,” notes Bohner.

Early summer scouting will also help diagnose problems such potassium deficiency. “You can see the yellowing around the edge of the leaf and chlorosis,” says Bohner. Unfortunately not a lot can be done to remedy the situation. “It’s pretty tough to get that macro nutrient in through the leaves. If it rains and the problem is bad enough, sometimes we will recommend putting on dry product.”

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When growers spot potassium problems, Bohner suggests they grab a shovel and check out plant roots. “The potash deficiency sometimes is a symptom of soybean cyst nematode. It’s important to check roots for the tiny ‘pithead’ cysts on the smaller roots and root hairs,” to determine whether SCN has a foothold in the field.

Growers also need to be on the lookout for aphids. “Often it’s the potassium-deficient plants that the aphids reproduce more quickly on and that’s where they are the most intense in terms of numbers.”

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