Mike Kilen

mkilen@dmreg.com

Debate over the causes of Iowa’s water quality problem typically centers on agriculture. But some observers have questioned whether city dwellers share responsibility for one item of particular pride.

The perfect lawn.

A carpet of turf grass free of weeds often requires nitrogen and phosphorus fertilizers — the same chemicals that Des Moines Water Works says are leaching from farmers’ fields and into Iowa waterways, prompting the utility to sue three rural Iowa counties’ drainage districts.

“Everyone can do things to protect our water quality, whether they live in town or on the farm,” said Iowa Department of Agriculture spokesman Dustin Vande Hoef, pointing to 22 urban water quality demonstration projects launched by the department's Clean Water Iowa program, nearly the same number of projects as on agricultural land.

But some scientists say the impact of treated lawns on water quality is relatively minor.

It may even venture into the realm of exaggerated myth.

One statistic widely disseminated through national media and online sources last year indicated that 40 to 60 percent of nitrogen applied to lawns through fertilizer winds up in surface and groundwater, a percentage attributed to the Environmental Protection Agency.

But EPA officials say there is no universal value on how much ends up in groundwater and couldn’t confirm those findings. And other research the agency cites shows that well-maintained lawns actually lead to less water runoff and nitrogen loss.

A state study on the origins of pollutants in the Raccoon River near Des Moines showed that turf grass and pasture accounted for only 1 to 1.5 percent of the maximum daily load of nitrogen, while about 85 percent came from agricultural sources, said Chris Jones, hydroscience researcher with the Iowa Geological Survey.

“The scientific literature is not very supportive of the idea of nutrient loss, and especially nitrogen, from turf grass," Jones said.

“There is also a fair amount of monitoring data in Iowa that shows nitrate concentrations actually decreasing as streams flow through an urban area like Des Moines.”

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That includes water flowing past heavily treated golf courses. Jones' research colleague, Keith Schilling, is in the midst of a two-year study of six Iowa golf courses, whose preliminary data show that most of the courses have low nitrogen and phosphorus concentrations in soil and shallow water.

He cautions that the courses are tended by turf professionals who take great pride in proper application.

“The reason that golf courses look so good is not because they are using more. They just know how to use and control it,” said Jim Novak of The Lawn Institute, which represents turf grass producers. “The problem isn’t turf grass; it’s the person doing the application.”

Ned Chiodo, who manages three municipal golf courses in Des Moines, said he uses only a quarter-pound of fertilizer per acre, and only on the fairways, leaving a thick buffer of rough to prevent surface runoff. He also tests the soil to determine exactly how much fertilizer to use, because he wants to save money.

Residents use too much fertilizer on their lawns, he said, and then compound the error by overwatering, flushing it all away.

Most of the 63,000 square miles of turf grass in the U.S. is on residential lawns. Yet research has concluded that there is very little movement of nitrogen through soil, and phosphorus is slow to move off the landscape, said Nick Christians, professor of horticulture at Iowa State University.

Proper application is key. He said a standard annual load is 3 pounds of nitrogen fertilizer over 1,000 square feet of surface.

Environmental activists agree — to a point.

“Urban runoff does contribute to nitrogen and phosphorus pollution in our rivers and streams; but the amount is a fraction of agriculture’s contribution,” said Neila Seaman, Iowa chapter director of the Sierra Club.

That said, she recommends having a soil test, and apply only the amount of fertilizer needed; also, pick up pet waste, which can contribute to nitrogen runoff into storm sewers.

Experts say a spring and fall application is typical, but it should be applied during periods when the grass is growing. Sweeping grass clippings or errant fertilizer from hard surfaces back into the lawn also helps decrease the load.

The proximity of lawns to a waterway is also a key factor.

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Walnut Creek runs 70 miles in central Iowa, and half of those miles are through Des Moines urban areas. That’s why Walnut Creek Watershed Coalition founder Darren Fife has approached Windsor Heights city officials about a buffer plan, a recommendation to residents not to mow within 20 to 30 feet of the creek.

“It’s not just a rural problem,” he said.

His organization is also considering promoting a series of “No Spray Neighbor” signs to encourage people “who aren’t just concerned about the greenest grass” to not use herbicides.

Christians said research has shown that herbicides often included in lawn treatment packages are safe. But environmental experts say that the treatments can promote a monoculture that limits diversity.

“Weed killers reduce flowers, which bees use as forage,” said Mary Harris, an assistant professor in natural resource ecology at ISU. “No flowers, no bees.”

Phosphorus can be a larger issue for lawns in lake regions.

While much of Iowa’s water issues center on rivers and streams, officials in lake areas such as Okoboji and Clear Lake encourage residents to limit the use of phosphorus in fertilizer, and lake-dominated Minnesota prohibits its inclusion in lawn fertilizer. Similar legislation was proposed in Iowa in 2009 but failed.

Excess phosphorus can create scummy algae blooms in a lake that are not only aesthetically displeasing, but create toxins dangerous to humans.

Rich Leopold has a vacation home in Okoboji and is director of Polk County Conservation, which is devoting resources to identifying water quality issues in Easter Lake in Des Moines. He said the issues are the same, whether rural or urban. One can’t complain about farmers if you’re mowing and shooting grass clippings into the lake.

He has taken pride in having a “Darwinian lawn” at the lake, allowing the strongest species to survive without his interference, but even he said neighbor peer pressure gets to him.

He’ll take after the creeping Charlie or thistles with a shot of weedkiller and feel OK about it.

“It’s not to say that you don’t have a responsibility in an urban setting, but I’m a scientist,” he said. “Where do you spend the money to solve the problem — on urban lawns or agriculture?"