Great Lakes agriculture generates more than $15 billion a year and it accounts for 7 percent of total U.S. food production. But fertilizer runoff from farm fields is a major source of pollution in the lakes.

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Summers along the Great Lakes include fishing, boating -- and dangerous algae blooms that can shut down beaches. These blooms are caused by excess phosphorous, a lot of which comes from farms. Now some of the region's farmers are testing agricultural practices that could reduce harmful runoff.

Environmental and state leaders in New York are calling on Ohio to get its phosphorous run-off into Lake Erie under control.