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Iowa manure management plans face scrutiny over water quality
Farmers say current system protects water while keeping costs down, but environmental groups pin the plans as a piece of Iowa’s water quality crisis
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Sen. Ken Rozenboom and his family have farmed and raised hogs for decades in south central Iowa.
The Rozenbooms, like most livestock operators in Iowa, collect the hog manure in on-site lagoons, pump it into tanks and transport it to nearby fields where it is incorporated into the soil as fertilizer.
Like other medium to large livestock operators in Iowa, Rozenboom has a manure management plan on file with the Iowa Department of Natural Resources and he calculates annually the amount of manure, based on the nutrients phosphorus and nitrogen, that can be applied to the field.
This system, according to Rozenboom, means all of the manure in his operation is accounted for and the cost of fertilizer keeps farmers from over-applying to any particular field.
“This isn’t done willy-nilly, like some people seem to think it is,” Rozenboom said. “It’s very precise.”
But water quality advocates in the state say these manure management plans do not sufficiently regulate the massive amounts of manure produced by Iowa’s concentrated animal feeding operations. This in turn, they say, contributes to consistently high nutrient concentrations in Iowa rivers, lakes and drinking water.
Iowa Environmental Council and Food & Water Watch have called for greater enforcement of the manure management plans, an online database of the plans and for farms to avoid over-applying nutrients.
The environmental groups argue too much of the livestock industry’s waste ends up in Iowa waterways and negatively impacts the health of Iowans and the environment.
What is a manure management plan?
Manure management plans are required in Iowa for any confined, meaning totally roofed, livestock feeding operations with a total animal unit capacity of more than 500 units.
The plans includes estimates, based on established values from the farm, of the amount of manure, plus the manure’s nitrogen and phosphorus concentrations.
The second part of the plan requires farmers to determine the maximum manure application rate for each of the fields where they plan to apply manure. This amount is determined using information on crop rotation and proven yields to determine how much nitrogen and phosphorus would be taken up by the crop.
Under the manure management plan, farmers are not allowed to apply amounts of manure that would exceed these nutrient limitations on each field.
On farm records
Manure application records are not submitted to DNR, but are kept on farm in case the department decides to audit a farm’s manure plan.
In a conversation explaining manure management on his farm, Rozenboom displayed a sheet of notebook paper where his great nephews had meticulously recorded, by hand, the date and amount of manure applied to each of the fields in his manure plan.
Critics of the plan argue these records should be submitted to DNR as part of digital, public record.
Michael Schmidt, general counsel with Iowa Environmental Counsel said records, like air emissions and solid waste discharges are public in “every other industry.”
“We clearly see that some of the nitrogen is getting from these agricultural sources into public water supplies and causing issues downstream,” Schmidt said. “This is an issue of public concern, and so it does not make sense to keep that confidential when people downstream are being directly affected.”
Daniel Andersen, an assistant professor at Iowa State University and a manure specialist with the university extension program, said this information is not public, likely because it’s viewed as proprietary information for a farmer.
“Most farms today, I don’t think they’re putting on malicious amounts of manure on purpose,” Andersen said. “ I think generally, fertilizer prices have risen enough, relative to the cost of manure application, that they’re trying to use manure responsibly.”
Plus, Andersen noted, farmers who rely on commercial, non-manure, fertilizers, are not required to report the amounts they applied, nor adhere to a nutrient limit.
Because manure is difficult and expensive to transport, it works out that 25 percent to 30 percent of all nitrogen, phosphorus and potassium used to support crop production in the state comes from manure. The rest of those needs are met with synthetic fertilizers, according to Andersen.
Schmidt with Iowa Environmental Council said it’s also problematic that manure management plans, while public, are not more accessible.
Tammie Krausman, the communications director with DNR, said the manure management plans are “available for review at the field offices or via public records requests.”
Records maintained by the facility to demonstrate compliance with the plans are “statutorily mandated as confidential records” Krausman said.
Schmidt said this means that even if a neighbor suspects someone is doing something wrong on their field, “there’s no way that they can prove that by checking the records.”
Rozenboom argued that “spot checks” work in a number of systems to keep players honest. Plus, the economics mean a farmer wouldn’t want to apply more manure than what his field needed.
The way the math works out, the manure he applies is worth about $280 per acre in nutrients.
“Now, I don’t know too many people, farmers, or otherwise that are gonna burn half their money – they can’t afford to do that,” Rozenboom said.
Andersen said manure management plans typically include more fields than where a farmer typically applies manure to account for a year where they might have more manure than they planned for.
Audits
While some of the records are not public, DNR can request them from farmers at any time, and they are reviewed by the department in the event of an audit.
According to Krausman, in 2025 DNR staff conducted 745 onsite inspections of animal feeding operations that would have included a review of manure management plans.
Krausman said DNR has “consistently pursued enforcement actions” since 2020 for animal feeding operation violations like late manure management plans, construction violations and prohibited discharges.
“A top priority for the DNR is manure discharges that reach state waters,” Krausman said in an email. “All such incidents are referred to DNR Legal Services for review and potential further enforcement action.”
Since 2020, DNR has issued 97 enforcement actions related to manure management plans and 62 enforcement actions related to prohibited discharges at animal feeding operations.
The environmental group Food & Water Watch issued a blueprint for clean water in Iowa, with a slew of legislative suggestions that would “ensure that Iowa’s water is drinkable for generations to come.” Several suggestions related to manure management in the state.
The blueprint called for a “publicly available database” with manure management plan data, requirements for DNR to inspect one-fifth of all permitted animal operations annually and a mandate that farms monitor for discharges “during and immediately after land application.”
DNR relies on producers and the public to report spills of manure and other contaminants that end up in Iowa waterways. An analysis from Food & Water Watch, using DNR records, found that between 2013 and 2023, there were 179 instances of manure discharges to Iowa waterways, killing approximately 2 million fish over the time frame.
Food & Water Watch’s proposed solution is to mandate that all large concentrated animal feeding operations require federal discharge permits that are enforced by the U.S. Environmental Protection Agency.
Dani Replogle, an attorney with Food & Water Watch, said these permits would give “transparent information” to the public and regulators about pollution entering waterways.
“We need federal nutrient management plans instead of Iowa’s manure management plan, and we need those permits to include monitoring so that we can see what’s actually happening, what pollution is coming off of these facilities, and then have a way to force facilities to make changes when it comes out that they are polluting water,” Replogle said.
Replogle said manure management plans are a “completely inadequate way to address the pollution crisis” in Iowa, because the plans are written by farmers.
“It’s really a case of the fox guarding the hen house,” Replogle said.
A limit, not a recommendation
Andersen said the biggest point of confusion he sees with manure management plans is that producers will often view the nitrogen and phosphorus maximums as an application recommendation.
“I think for a long time, people thought of it sort of as a recommendation tool – that’s how much nitrogen I should be putting on – and that’s not the case,” Andersen said.
He explained that while the current nitrogen use factors in Iowa, as shown in part of the manure management plan, range from 0.9 pounds of nitrogen per bushel, to 1.2 pounds per bushel, data gathered from on-farm trials by the Iowa Nitrogen Initiative show that on average, farms need 0.93 pounds of nitrogen per bushel of corn.
Andersen said these trials give a recommended amount of nitrogen that should be applied, which is lower than the value that most farmers can put on their manure management plan.
“The manure management plan is sort of setting a limit of where most fields won’t be nitrogen limited,” Andersen explained. “It is not a nitrogen recommendation tool, and shouldn’t be treated as such.”
He said in most manure-applied fields, farmers try to apply manure as close to the nutrient limits as they can.
Part of this, he explained, is because it takes about 60 working days to apply all of the estimated manure produced in Iowa each year. Add in rain delays and the time it takes to move equipment and the reality is more like 80 to 90 days needed for application.
“It’s easy to sit and say, ‘We should legislate so that no one’s allowed to put manure on before X date on the calendar’ but if we don’t have the capacity to do that, we run into other issues,” Andersen said.
Replogle with Food & Water Watch said in addition to nitrogen and phosphorus running off a field and into waterways, manure application can lead to other types of pollution. Replogle said things like fecal coliform bacteria, chloride, heavy metals and traces of antibiotics are all pollutants that could be in manure.
“There’s a lot of other stuff in CAFO waste that is not being accounted for with a manure management plan or a nutrient management plan for that matter,” Replogle said.
Andersen said when it comes to manure application’s relationship with water quality, ground cover, rather than application rate, is more important.
A field with vegetation in the ground is more likely to hold on to nutrients, especially during a rain event, than an empty field.
“Cropping system matters a lot, and we need to try and encourage having vegetation all the time,” Andersen said.
The state-led Iowa Nutrient Reduction Strategy has encouraged farmers to adopt cover crops and optimized nitrogen application strategies as methods to reduce the nutrient load ending up in Iowa waterways.
The state has also implemented grants and funding programs to help establish vegetation along waterways, saturated buffers and other strategies aimed at improving nutrient concentrations in watersheds.
A group of Iowa Democrats previewed legislation to improve water quality in the state. The plan did not include farm regulations, but called for a boost in the incentives to farmers and landowners to implement these strategies.
“I worry less about an individual farm’s records, and more about, how do we generally help support farmers, use manure as a resource, make better manure decisions,” Andersen said. “Because I think generally people are in compliance – our real problem is that people are applying close to that manure management form (limit).”
This article was first published by Iowa Capital Dispatch.
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