Conservation measures by farmers have reduced nitrogen and phosphorus runoff in Iowa and other states in the Upper Mississippi River Basin, according to a federal government study released this week.
Using existing water quality data, researchers at the Agriculture Department and the U.S. Geological Survey determined voluntary agricultural conservation practices helped reduce nitrogen downstream in the Upper Mississippi River Basin watershed by as much as 34 percent. The impact on phosphorus reduction was less promising, with reductions topping out at 10 percent. Iowa is part of the Upper Mississippi and Missouri river basins.
In an interview Wednesday, Agriculture Secretary Tom Vilsack said the study provides evidence that investments by federal, state, local and nonprofit groups are improving water quality. He said more producers are using cover crops, not tilling their land and embracing precision agriculture to cut down on runoff of nitrogen, phosphorous and other pollutants from fertilizer and manure.
“Everyone knows there is the lawsuit in Iowa, and everyone knows my belief that the best way to resolve this is a rather significant investment in conservation,” Vilsack said. “There has to be some way of showing, of being able to document that what is being invested in is actually going to have the impact and effect. This study suggests that with that type of significant investment we could make a long-term difference.”
Des Moines Water Works sued drainage districts in three northwest Iowa counties last year, contending underground tiles in Sac, Calhoun and Buena Vista counties funnel high levels of nitrates from farm fields into the Raccoon River. That river is one of two sources of drinking water for 500,000 central Iowa residents.
Vilsack said he hopes that as lawmakers work on the budget and begin discussions about the next farm bill, the government’s report “would certainly emphasize the need for continued investment and continued support for conservation.” He said conservation can be successful by providing incentives to farms rather than requiring change through regulation.
The former Iowa governor estimated that since 2009, USDA has invested more than $29 billion to help producers make conservation improvements, with a record number of acres of private working lands enrolled in conservation programs during that time.
Craig Cox, senior vice president for agriculture and natural resources with the Environmental Working Group, said the report is further proof that conservation practices the organization has backed for decades can have a meaningful impact on water quality.
“That’s the good news,” he said. “The bad news is there is nowhere near enough land owners using those conservation practices, and that’s the reason the water quality is still so poor in those agricultural watersheds.”
Cox added that relying on voluntary action by producers or spending money to try to encourage them to use conservation practices hasn’t been enough.
“It’s time to look at more mandatory measures,” he said.
Ray Gaesser, who has adopted conservation practices on his corn and soybean farm in Corning, said more producers are interested in adopting conservation measures but “with the farm economy the way it is, farmers are reluctant to try anything new. They want to stick with something they know has worked for them, and trying something new is a lot more difficult when there is no or very little profit there.”
Kirk Leeds, chief executive officer of the Iowa Soybean Association, said the latest information shows that “our policies and investments that support this type of work are paying dividends.”
Still, he acknowledged that “we all recognize that we still have much work to do.”
The authors of the study, published in the journal Environmental Science and Technology, said that until now, nutrient reductions in streams have been challenging to measure. Non-agricultural sources and natural processes can make it difficult to determine how much improved farming practices are having on downstream water quality. The models used in this study adjusted for these outside factors, they said.
The report speculated there has not been more progress on phosphorus reductions in the Upper Mississippi River Basin because of long lags between conservation and the time it may take for sediment-bound phosphorus to move downstream. In addition, some erosion control practices, such as no-till and reduced tillage, have been shown to increase soluble phosphorus levels in farm runoff, which can potentially offset some benefits from erosion control practices.