The rain that swamped fields in recent weeks could heighten the risk of sulfur deficiency in crops.
Farmers growing canola are cautioned to monitor their crops for the deficiency, which can cause yields to plummet.
“It can easily cut your yield in half,” said Cynthia Grant, a research scientist at Agriculture Canada’s Brandon, Man., research centre.
Among the fields more likely to show a deficiency are those with well drained soils, especially if coarse soils are present. The torrents of rain increased the likelihood of some leaching in those fields.
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While soil testing can offer some clue as to whether sulfur is lacking, it has its problems. Fields tend to be variable in terms of sulfur content, making it difficult to get an accurate snapshot of what is needed for adequate nutrition.
“You can be in one spot and it’s deficient and step three steps and it’s in excess,” said Scott Day, a provincial agricultural representative at Boissevain, Man.
Symptoms of a deficiency in canola include cupping of the leaves and a purple coloring. Those signs can be detected as soon as the plants begin leafing, Day said.
This might be a tough year for farmers to decide the economic threshold for applying sulfur to compensate for a deficiency. Later seeding often translates into lower yields at harvest time.
But with canola, the extra cost has to be weighed against the benefits. A sulfur deficiency can translate into a less aggressive crop. Canola plants may also fail to set seed if they lack sulfur.
Grant advises farmers who are applying sulfur for this year’s crop to use a sulfate-containing source. She noted that elemental products need to be converted to sulfate before they can benefit the crop. That conversion can sometimes take years to occur.
Alfalfa is another crop where sulfur levels are important. But farmers growing alfalfa for hay may not be willing to invest as much in fertilizer as those growing seed alfalfa.
Alfalfa tends to have deeper roots than canola crops, said Gesa Racz, who heads the University of Manitoba’s soil science department. That gives alfalfa a greater chance of getting the sulfur it needs, even where leaching of nutrients has occurred.
“I wouldn’t expect to see any effects of these rains on alfalfa,” Racz said in an interview last week.
