Fertilizers contain nitrogen and phosphorus, and when strong rains saturate the soil, excess water runs off into rivers, bringing harmful nutrients with it, said Dr. Judy Zhang, a professor of environmental engineering at Case Western Reserve University who studies emerging contaminants.
"Because the algae grows, it needs a lot of oxygen, then that in turn is going to affect aquatic life," Zhang said. "Everything growing in the lake needs a lot of dissolved oxygen. (If they don't get it) fish will die and water will not be in a healthy condition. And when algae die, they become carbon sources, and that fuels the growth of microorganisms."
The farming community points to a recent dip in phosphorus in the Lake Erie watershed as proof its farming techniques make a difference.
"Of the main nutrients that go into algal blooms (phosphorus), we're seeing slight decreases of that coming into the lake, and I think that progress is going to continue," said Jordan Hoewischer, director of water quality research at the Ohio Farm Bureau Federation.
A variety of practices are responsible, he said. Farmers have put buffers between waterways and their fields, stopped tilling soil, and tested fields to keep excess nutrients to a minimum. The techniques work in tandem, Hoewischer said.
"There isn't one thing that each farmer can do that's going to improve everything dramatically," he said. "It's really about taking an a la carte approach."
A working farm at the Molly Caren Agricultural Center, which is part of the Ohio State's college of food, agricultural and environmental sciences, provides a testing ground.
"We have found that phosphorus and nitrogen both need a different level of management to keep them out of the watershed," Douridas said.
Farmers throughout Ohio use those practices.
Ben Bowsher planted grass and dug ditches around the fields of his 1,600-acre Allen County farm where he and his wife Stephanie grow corn, soybeans and wheat. The trenches and grass pastures form a buffer blocking erosion and runoff.