DES MOINES, Iowa (AP) - Nitrogen pollution flowing out of Iowa to the Gulf of Mexico has grown by close to 50 percent over nearly two decades, a new report shows, despite hundreds of millions of dollars spent to stem nutrients entering the state’s waterways.

A University of Iowa study shows the state’s contribution to the Gulf dead zone spiked 47 percent to 618 million pounds in 2016, based on five-year running annual averages.

“Just based on water quality data, I think we can say we’ve not made much progress over the past 20 years in terms of nitrogen,” said Chris Jones, a research engineer at the UI’s IIHR-Hydroscience & Engineering.

Environmentalists say the study raises new questions about the effectiveness of Iowa’s approach to improving water quality and its reliance on voluntary ag compliance.

“We’ve been pouring state and federal money into cutting nutrient pollution for decades, and this highlights the fact that the voluntary approach is not working,” said Jennifer Terry, executive director of the Iowa Environmental Council.

“We’re not headed in the right direction. … We need to follow the lead of other states and pass some environmental laws that will actually reduce loads and result in cleaner water,” Terry said.

The Des Moines Register reports that the news comes as Iowa marks the five-year anniversary of the Iowa Nutrient Reduction Strategy, a plan designed to cut by 45 percent the nitrogen and phosphorus levels that leave Iowa and feed Gulf hypoxia - or the dead zone.

Oxygen levels within the zone are so low that marine life can no longer survive, threatening the Gulf’s seafood industry.

Most of the nutrient losses come from farming, although the strategy also targets losses from urban wastewater and industrial operations.

Last year, Iowa invested $420 million in those water quality improvements, including helping farmers plant cover crops, build terraces and tackle other conservation practices that hold nutrients in place.

But farmers expanding their drainage tile systems - along with increasing hog, cattle and chicken feeding operations, which provide manure to fertilize crops - likely outweigh those conservation efforts, UI scientists say.

The nutrient reduction practices “being implemented are a tiny, tiny portion of what needs to be done, and it’s occurring in a system that’s changing,” Jones said.

“We appreciate all that is being done with nutrient management and conservation farming. Unfortunately, we’re just impacting too few acres with too few practices,” added Larry Weber, executive associate dean for UI’s College of Engineering.

Jones wrote the study with Weber and Keith Schilling, another UI research engineer.

Increased nutrient pollution in water creates problems for people and animals beyond the dead zone. High phosphorus levels can lead to toxic algae blooms that can befoul lakes, rivers and streams, potentially killing pets and making people ill.

And the federal government limits the amount of nitrates in drinking water to 10 milligrams per liter. Higher levels can be fatal to babies under 6 months old.

Increased levels translate to higher costs for utilities for nitrate removal.

“We need a dramatic increase, a rapidly-scaled up increase in conservation practices and more funding,” said Cindy Lane, the Iowa Environmental Council’s water program director.

Schilling said the study shows that targeting nutrient reduction investment in Iowa can have a significant impact downstream.

“Iowa has a dominant role in this Gulf hypoxia issue,” Schilling said. “Let’s invest the resources here, where we really need it.

“If we solve Iowa, we solve the Gulf,” he said.

The UI study gives Iowans new information in the fight to reduce the nitrogen levels that flow from the state into the Mississippi and Missouri rivers, which make their way to the Gulf of Mexico.

Looking at Iowa Department of Natural Resources data from 23 monitoring stations, the study shows Iowa on average over the past 18 years contributed 29 percent of the total nitrogen headed to the Gulf from the Mississippi-Atchafalaya river basin.

The river basin is a massive watershed that includes all or part of 31 states.

Iowa’s nitrogen impact was even greater in other watersheds.

The state averaged 45 percent of the nitrogen levels going into the Upper Mississippi River basin, and 55 percent of the nitrogen going into to the Missouri River basin.

“When you look at the entire Missouri (River) watershed, our land comprises 3.3 percent of the total area … and Iowa contributes nearly 12 percent of the water,” Jones said.

But “we contribute 55 percent of the nitrate,” he said.

“The way that pencils out is that the amount of water coming from Iowa has seven times more nitrates than the rest of the Missouri River watershed,” Jones said.

If Iowa’s contributions were removed, the Missouri River would have little nitrogen contributions in some years.

“We really need to take seriously the Missouri River’s contribution as a driver for Gulf hypoxia,” Jones said.

The growing concentration of livestock feeding operations in western Iowa might account for Iowa’s large contribution to the Missouri River nitrate levels, the scientists said.

“People tend to dismiss livestock influences, but maybe there’s more to it than people give credit it for,” Schilling said, adding that it would require more study to determine the impact.

Iowa’s nitrogen levels, based on running five-year annual averages, have been above the 2003 value for 10 consecutive years, the study says.

The scientists say 2003 was the first year the five-year rolling average could be calculated, with data that starts in 1999.

The goal of the Gulf Hypoxia Task Force, made up of federal, state and tribal leaders, “will be very difficult to achieve if nitrate retention cannot be improved in Iowa,” the report said.

The task force, with Iowa Agriculture Secretary Mike Naig as chairman, seeks to reduce the dead zone to 1,900 square miles by 2035. The deadline was extended from 2015.

Last year, the dead zone set a record, which, at 8,776 square miles, was more than four times the goal size.

The report says about 90 percent of Iowa’s nitrogen levels “can be sourced to the 72 percent of the state’s land area that is in crop cultivation.”

Iowa, an agriculture powerhouse, is a national leader in corn, soybean, pork, egg and beef production.

“This intense production of carbohydrates and protein has resulted in the state being a leading contributor” to the nitrogen loads and Gulf hypoxia, the report said.

Naig said farmers understand the important role they play in improving water quality and are scaling up efforts across the state “as we move from demonstration projects to larger, watershed-scale implementation projects.

“We recognize that there is still a lot of work to be done, but we are on the right path,” said Naig, who adds farmers are working with more than 250 partners in 65 rural and urban demonstration projects.

The UI scientists doubt that increased cropping is the reason for the increased nitrogen impact.

Iowa’s cropped area has increased only 4 percent over the past 18 years, while other states’ farmed land has climbed 21 percent, particularly in Minnesota, North and South Dakota and Kansas.

About 85 percent of Iowa’s acres are farmed, making it the fifth-highest in the nation, based on the 2012 U.S. Agriculture Census, so there are few acres left that can be brought into production compared with other states.

“Iowa’s decline in the share of the region’s soybean area was especially pronounced, dropping from 18.6 percent in 1999 to 14.5 percent in 2016,” the report said.

“One would expect our (nitrogen) contributions relative to the other areas would be diminished,” Jones said. “But the opposite has occurred.”

Jones said it’s led the scientists to consider other factors.

The scientists doubt that Iowa farmers are using significantly more fertilizer.

“When we look at nitrogen sales data, it might change a little year over year. But on a per acre basis, that hasn’t changed a lot since 1990,” he said.

And with little increase in corn and soybean acres, the scientists speculate that Iowa’s increased nitrogen levels could be coming from more drainage tiles.

Or farmers could be using more manure as fertilizer from animal feeding operations.

Without Iowa, the Gulf’s overall nitrate loads would have declined 43,400 tons over 18 years, based on five-year running annual averages, the scientists’ data show.

Instead nitrate loads grew by 52,000 tons.

“It’s pretty clear these loads from the Ohio basin have to be declining,” Jones said. “A lot that is coming from Indiana.”

That state’s high level of cover crop adoption by farmers could be the reason, he said, and should be studied.

Cover crops such as cereal rye slow the rate of water runoff, reduce erosion and improve soil fertility.

Iowa also needs to honestly discuss the impact that drainage tiling has on nitrogen losses, Jones said.

Iowa doesn’t collect data on how much underground drainage runs through the state, although officials estimate about 9 million acres are drained through tile.

Environmentalists believe the number is much higher.

Underground drainage tile helps improve yields by quickly removing excess water from fields.

Iowa’s tiling system consists of a network of drainage lines that feed into large pipes. The massive network, first constructed in the 1920s, ‘30s and ‘40s, turned once swampy lands into some of the nation’s most productive farmland.

But water quickly carried away by the tiling system misses cleansing that would naturally occur by filtering through soil or the roots of trees, shrubs and grasses in riparian buffers along streams.

Des Moines Water Works unsuccessfully sued drainage districts in three north Iowa counties in 2015, claiming underground tiles funneled high levels of nitrates into the Raccoon River, a source of drinking water for 500,000 central Iowa residents.

“We acknowledge that it’s important to track implemented conservation, and we encourage that,” Jones said.

“But we also need to have the courage to talk about these things that drive the system in the other direction.”

Terry said Iowa is “one of the most heavily tiled states in the nation,” and its 110-year-old law regulating the practice does little to protect water quality.

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Information from: The Des Moines Register, http://www.desmoinesregister.com

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