Drastic measures, such as taking 30,000 acres, or 6,300 farms, out of cash-crop production, are needed to curb algae growth in Lake Erie, says a study released by the University of Michigan Water Center.
The researchers found that current efforts to keep phosphorus, which is found in livestock manure and artificial fertilizers, on fields instead of flowing into the lake are falling drastically short of results needed to achieve a 40 percent cut in runoff.
That’s the target set in February by the International Joint Commission which includes Canadian and U.S. authorities.
Excessive levels of the nutrient are the leading cause of increasingly massive blooms, which in 2014 left more than 400,000 people in Toledo, Ohio, and southeastern Michigan unable to consume tap water for two days because the bacterial algae produce a toxin.
Another bloom last year was the largest on record. Phosphorus also causes a "dead zone" in Lake Erie's central basin with so little oxygen that fish cannot survive.
Ohio and Michigan rely largely on voluntary compliance, but too few farmers are participating, the report found.
In Ontario farmers have been regulated by Nutrient Management Plans which basically limit fertilizer and manure applications to what that year’s crop will use.
But it’s also clear that Ontario farmers will be expected to further reduce phosphorous erosion over the next five years. They have been reducing tillage, planting cover crops, stopped spreading manure on frozen ground, set aside vegetative strips along streams and rivers, fenced livestock out of streams and invested in expensive manure storage facilities.
Policy alternatives described as "most promising" by Jay Martin of Ohio State University, the report's co-author, include widespread use of the best-management practices and conversion of some croplands to switchgrass or other grasses.
One called for removing nearly 30,000 acres in the watershed from production. That's the equivalent of 6,300 farms, as the average farm in the area consists of 235 acres.
Jeff Reuter, past director of Ohio Sea Grant and a Lake Erie specialist who wasn't involved with the study, said some cropland is so overloaded with phosphorus that turning it into grassland or wetlands is the only way to stop runoff.