Growers topdressing melted urea to boost wheat protein should be asking their supplier whether it contains a contaminant that’s toxic to wheat, suggests a soil scientist at the University of Manitoba.
With the introduction of higher yielding wheat varieties, there’s been new interest in applying post-anthesis nitrogen to wheat to boost protein content in Western Canada. Some companies are offering melted or dissolved urea as a “safer” alternative to the traditional UAN 28-0-0 liquid fertilizer because it’s less likely to cause leaf burn and crop injury.
And yet, there were severe cases of leaf burn reported in wheat fields where melted urea was applied in Manitoba and North Dakota last year.
Researchers at the University of Manitoba and North Dakota State University say the damage was likely related to the source of the urea. If the manufacturing process is poorly regulated, it can produce a toxic byproduct called “biuret.” North American manufacturers generally keep biuret content in urea below toxic thresholds, but that might not be the case with urea from other sources.
“There’s been some trouble with some urea that has high biuret being used for urea solutions and causing crop damage,” explains the U of M’s Don Flaten in this Wheat School update.
“You want to make sure whatever urea solution you’re spraying on your plants is very low in biuret. Even 1 percent or greater could be a toxicity problem.”
Flaten recommends asking your retailer to see if they have a spec sheet from the manufacturer that shows or guarantees the product does not contain high biuret levels.