More than $430 million a year is being spent to reduce farm runoff in Iowa, according to a new study by Iowa State University.
The study also predicted it would cost $613 million per year to reduce farm-field phosphorus by 40 percent and nitrates by 25 percent.
The focus on the quality of Iowa's lakes and streams has risen in recent years as the number people using the waterways for recreation has grown.
Iowa waterways have some of the highest fertilizer concentrations in the world, high algae growth and low oxygen levels.
The Environmental Protection Agency is requiring states to come up with the nation's first limits on nitrogen and phosphorus, which occur naturally and are main ingredients in fertilizer.
The Iowa Farm Bureau Federation joined Iowa State and other commodity groups to pay for the $70,000 study. The groups wanted to determine how much farmers currently spend to curb runoff and what it would cost to meet the EPA standards.
"We asked the question, 'What's it going to take in this state to address our needs?'" said Rick Robinson, environmental policy director for the Farm Bureau Federation.
Current practices used in Iowa cut nitrate runoff by 6 percent to 28 percent, and phosphorus levels by 25 percent to 58 percent. The practices include terraces, grassed waterways, contour farming and no-till farming.
Robinson said the study shows that practices varied across the state and emphasizes the need to target practices used and how much is spent on the projects.
"One size does not fit all," he said.
"Our results indicate that the most cost-effective measures to improve water quality are different across different watersheds, and that targeting different pollutants will mean different land use options," said Catherine Kling, ISU's lead researcher on the study.
The Iowa Department of Natural Resources is expected to make preliminary proposals next year on nitrates and phosphorus in Iowa waters.