Iowa’s longest drought in 70 years may have caused a buildup of nitrates on farmland, which could significantly increase river pollution, state water quality monitors say.
Research shows that nitrogen fertilizer not used by crops can be quickly washed away from those fields after a drought year, and Iowa’s drought has lasted more than three years.
Nitrate leaching is often most noticeable during heavy spring rains, when fields have been fertilized but crops have not yet grown.
“These extreme events are quickly becoming the norm,” said Chris Jones, a former University of Iowa researcher who studies the effects of agriculture on water quality. “If we get back to this wet regime, it’s going to be epic.”
For example: In 2013, record spring rainfall helped the state recover from the worst of the drought. As a result, the amount of nitrates detected in Iowa streams increased by more than 400% from 2012 to 2013, according to data collected by the Iowa Nutrition Research Center.
Nitrate pollution in 2013 was almost the worst in 20 years, considering river flow data. The absolute amount of nitrate in rivers across the state was on the rise until 2016.
State climatologist Justin Glisan said climate projections suggest this spring could be warmer and wetter than usual. That increases the chance of thunderstorms and associated heavy rain, but it’s unclear whether this spring will be anything like 2013, he said.
Nitrates will increase further in 2022
Nitrogen is a critical nutrient for Iowa corn to ensure maximum crop yield. It is often added to fields along with chemical fertilizers and livestock manure.
However, it poses environmental threats across sectors. Rivers are important sources of drinking water in large cities, especially the Des Moines metropolitan area, and nitrates may need to be removed from the water to make it safe to drink. Des Moines Water District spent about $150,000 on nitrate removal in 2022.
Additionally, elevated levels of nitrate and phosphorus, another prominent nutrient, can wreak havoc on aquatic ecosystems, with algae blooms depleting oxygen in the water and releasing toxins that are harmful to swimmers. is released.
Crop fertilizers are a major cause of dead zones in the Gulf of Mexico.
Nitrate releases into Iowa’s rivers are facilitated by the state’s vast network of underground tiling. These perforated pipes not only drain wet fields to improve crop productivity, but also provide a pathway for nitrates to flow more quickly into the river.
According to Iowa State University, about half of the state’s farmland is drained with tiles, and farmers continue to install more tiles.
(A recently released study by the U.S. Department of Agriculture shows that basement tiling has declined in recent years, but it’s unclear why.)
In drought years, nitrate and phosphorus levels in rivers are expected to decrease. There is less water-absorbing nitrate in the soil and less surface erosion that causes phosphorus leaching.
That’s reflected in the state’s river monitoring data, which saw nutrient loads drop to their lowest levels in 20 years in 2020 and 2021.
Parts of Iowa have been suffering from drought since July 2020. Approximately 79% of the state is currently experiencing some degree of drought.
But in 2022, stream nitrates increased (according to recently released monitoring data by the state). That’s despite the state’s average precipitation in 2022 being slightly less than in 2021.
Matt Helmers, who heads the Nutrient Research Center, believes the spike is due to nitrate buildup during drought and rain during the months when crops aren’t growing.
State weather data shows just three months of 2022 saw above-normal precipitation: March, November and December. All of these are outside the state’s traditional crop growing season.
Commercial fertilizer sales also hit a new record in Iowa in 2022, with farmers increasingly fertilizing their fields in the fall, according to the Cedar Rapids Gazette. Nutrients remain in the soil for extended periods of time when crops are not growing, creating the potential for further river pollution.
State agriculture officials have become increasingly focused in recent years on helping farmers implement field-edge conservation practices. The project aims to slow the release of surface runoff and groundwater flows and remove nutrients from them before they reach rivers.
Helmers said the impact of that work on water quality across the state is not yet clear.
“The monitoring that people are doing shows that these practices are effective, but we need to realize that they are still dealing with a fairly small percentage of the landscape,” he said. Told.
Stream monitoring overcomes budget cuts
Last year, Republican lawmakers cut the research center’s funding by a third and transferred that money to the Iowa Department of Agriculture and Land Management to pay for the project.
This $500,000 per year is equivalent to the amount the research center spends to operate the Iowa Water Quality Information System, which aggregates real-time nitrate pollution data. Opponents of the move feared it would destroy the regime.
“Without data, it’s easy to say there’s no problem, or we don’t know how to measure the problem,” Sen. Janice Weiner, D-Iowa City, said last year.
In return, the research center cut funding to the system by a third. Larry Weber, director of water science and engineering at the University of Iowa IIHR, which runs the system, said there is still enough funding to operate the network of 70 monitoring sites.
Weber said the monitoring site is especially valuable because it can continually update data on nitrate concentrations, whereas other monitoring by the Iowa Department of Natural Resources occurs once a month. (DNR samples a wider range of contaminants.)
Data from both monitoring sites are used by the Nutrient Research Center to calculate annual nutrient loads.
While the funding cuts are not expected to disrupt the UI monitoring network itself, it will hinder analysis of the data it generates.
“Collecting data is easy,” Weber said. “Our staff provides excellent support to his ISU Nutrition Research Center, which relies on researchers for analysis and evaluation.”
Opinions differ on progress
The state’s nitrate data shows an overall decline in river pollution in recent years, but the drought makes it difficult to determine what the overall trend is. Opinions vary on this trend.
— helmersat the research center: “It’s hard to say from year to year,” he says, adding that a so-called “batch-and-build” conservation program pioneered by the state in Polk County has led to faster adoption of edges. – Field practice.
That idea of building bioreactors and buffers along multiple farms in a small area was adopted by state agriculture officials and has now been chosen as one of the main weapons against river pollution.
“We still need to scale up,” Helmers said. “Embrace more of these practices.”
— don mcdowelldirector of public affairs for the state Department of Agriculture and Land Management. “Iowans recognize that variable weather will always create ups and downs in achieving long-term nutrient reduction strategy goals,” he said. .
McDowell did not comment specifically on the department’s view of long-term trends, but said the state “broke conservation and water quality adoption records in each of the past two years.”
The state’s recent efforts have more than doubled the amount spent on conservation efforts since the state adopted a nutrient reduction strategy in 2013 that prioritizes farmers’ voluntary efforts to curb pollution. The goal is to reduce the amount of nitrogen and phosphorus emitted from fields by 45%.
McDowell noted that farmers now plant cover crops on nearly 4 million acres of farmland, compared to almost none 10 years ago. These crops are planted in empty fields after harvest to prevent erosion and absorb nutrients that could flow into rivers. The acreage represents about 17% of the total area planted to corn and soybeans each year.
“We know that these water quality controls work, and we are firmly committed to accelerating the pace of their implementation,” McDowell said.
Farmers are sometimes hesitant to change their practices because of the risks that change poses.
“It may be a slower process than many would like, but from a farmer’s perspective, making the wrong decision can jeopardize your ability to stay in business,” said Jasper County farmer Roger Zylstra. ” he said.
— Alicia Vastwater program director at the Iowa Environmental Council: “Things are not going the way everyone wants them to be,” she said.
The council has criticized the state’s nutrition strategy and estimates it will take decades to reach its goals based on progress made so far.
Vast said at least farmers should be required to create a buffer zone between fields and streams, and fertilizer application should be more restricted.
— jones“I think there’s no question that the long-term trend for nitrogen is upward,” said the former UI researcher and author. “At the same time that we are doing conservation work, we are also making things worse.”
This includes installing a large amount of new drainage tile and increasing fertilizer use, he said.
“When you look at the new nitrogen loads from new tiles, it dwarfs conservation efforts,” Jones says.
The best solution to the state’s water quality problems is to diversify the crops it grows, with a shift away from its established focus on corn and soybeans, which would require a “divestment from ethanol.” He said that there is.
“Ethanol has to die,” Jones said. “We need to do that to improve this environmental condition in Iowa.”
That’s unlikely, at least in the foreseeable future. More than half of the state’s corn is used to produce ethanol, and state leaders are pushing to expand its use.
Additionally, despite the federal government’s goal of transitioning to electric vehicles, carbon dioxide pipelines could extend the life of the fuel.
A state report on the status of Iowa’s waterways is expected to be released by the U.S. Environmental Protection Agency in the coming weeks. The update, required every two years, will list streams, lakes and wetlands that the Iowa Department of Natural Resources considers “impaired.” Obstacles include contamination with nitrates and other pollutants, increased bacterial counts, and lackluster fish populations and diversity.
The DNR noted damage to more than 750 water bodies in its 2022 assessment.
