Province linked to 15% of Erie phosphorous

Agriculture federation hears from nutrient expert about ‘hot spots’

Toxic algae blooms in Lake Erie have been the cause of heated debate in the agriculture industry, mostly as they relate to phosphorous loading in rural areas of Ontario, Michigan and Ohio.

Farmers attending last week’s annual meeting of the Kent Federation of Agriculture got a better idea about how their work factors into the algae blooms.

According to Ivan O’Halloran, soil and nutrient expert at the University of Guelph’s Ridgetown campus, Ontario contributes between 15 and 18 per cent of all phosphorous into the lake through various means.

Much of that — up to 10 per cent — is through Lake St. Clair.

Comparatively, the news looks good for Ontario. Rivers such as the Thames and Grand are only estimated to add about 0.57 and 0.41 pounds of phosphorous per acre, respectively. That’s far less than the Sandusky River, at 1.26 pounds per acre, or the Cuyahoga River, at 1.52 pounds per acre.

But we shouldn’t go patting ourselves on the back just yet, O’Halloran said.

“We start talking about how we mitigate losses,” he said. “We know we have hot spots.

“The Thames River — there are some streams down near Leamington — we have to focus on those kinds of areas.”

The problem is fluctuation. Most years, phosphorous in Lake Erie does not exceed the recommended threshold of 11,000 tonnes per year. But many applications are weather-dependent, and more extreme temperatures or precipitation conditions can cause a spike in phosphorous runoff.

O’Halloran’s work focuses on limiting that fluctuation.

But pinpointing the solution for phosphorous overloading is not easy, and people in agriculture are worried that regulations to deal with Lake Erie may hurt their operations without helping phosphorous runoff at all.

“The bottom line is I’ve sat on committees where I’ve had other scientists argue that we should get rid of tile drains,” O’Halloran said. “And it’s scary, because they don’t understand what the purpose of tile drains are. And actually tile drains, if they reduce surface runoff, are actually a benefit.”

It was also asked whether urban centres, also a source of phosphorous, could have a role to play in limiting its availability in Lake Erie. But O’Halloran explained urban levels have been mostly constant since the early 1980s, when regulations finally started to lower runoff into the lake.

“I think the lowest-hanging fruit still is the idea of trying to control that surface runoff,” O’Halloran said.

“One of the things that I think might be having an impact now is the narrowing of tile spaces in terms of the total load going to the lake. Because of tile systems, we really don’t have anything that filters them once they leave the field.”

The next step might be conducting research on tile spacing, O’Halloran said. But research to that end has yet to be conducted in Ontario.