My first stint with Farm Progress as editor of its Minnesota and Dakota magazines during the 1990s included a story review by our new editorial director. The initial anxiety my fellow editors and I shared was eased by her compliments about each publication.
Except one.
“Do we really need three stories about nitrogen management?” she asked after reviewing an issue of Wallaces Farmer.
Well, yes.
Several decades later, nitrogen remains the lifeblood of Iowa corn production. Unfortunately, nitrogen in its nitrate form continues to bedevil water sources of major metropolitan areas. Concerns flared again this summer, when Des Moines Water Works — which manages the drinking water source for Des Moines and surrounding communities — banned lawn watering due to high nitrate levels.
Drinking water remained safe. Even so, the lawn-watering ban fueled social media comments such as:
- “Iowans shouldn’t have to drink poison.”
- “CAFOs and runoff from ethanol cornfields are making the water undrinkable, and we are spending millions cleaning up Big Ag’s mess.”
- “Because [water] is terribly polluted by farmers upstream.”
Ouch.
Leaky system
Here’s the thing: Agriculture is a major contributor to the elevated nitrate levels. Yet, it’s not because farmers recklessly apply commercial fertilizer and manure. It’s due to the nitrogen-leaking corn and soybean cropping system that’s the backbone of Iowa agriculture.
“We have an annual cropping system that leaves the soil vulnerable to leaching when the crop is not using nitrogen,” says Matt Helmers, an Iowa State University Extension agricultural engineer who directs the Iowa Nutrient Research Center.
That’s what happened this spring and summer, when rainfall flushed unused nitrate-nitrogen from 2024 and 2025 into central Iowa water supplies, Helmers says. Nitrates that resulted from mineralization — over which farmers have no control — also elevated levels, he adds.
All this has heralded calls for stricter fertilizer and manure regulation. This won’t fly in today’s political climate. Gov. Kim Reynolds opposes it, as do most Iowa legislators.
Yet, political climates change. What may seem impossible today may enjoy wide support a decade from now. The clock is ticking on improving water quality.
What to do?
“We need to think about what practices may be needed on individual parcels of land,” Helmers says. Some ideas include:
Improving manure management. Logistical reasons exist why early-fall manure applications occur, but they do lead to increased nutrient loss, Helmers says. At soil temperatures above 50 degrees, the manure in nitrogen converts to the nitrogen-losing nitrate form.
“If we can move applications later in the fall or into spring, we might be able to get more nitrogen into the crop rather than increasing the risk of loss,” Helmers says.
Better matching nitrogen with crop needs. The Iowa Nitrogen Initiative is conducting myriad trials to help farmers better match nitrogen with what crops require.
“Rather than having one or two N rates through the whole state, they are trying to estimate [N] needs per county,” Helmers says.
Covering up. “The more that we can get living cover on the land, the better off we can be from a nitrate loss perspective,” Helmers says.
Cover crops can scavenge excess nitrates from the soil profile. Ditto for small grains such as oats. Relay cropping that incorporates soybeans with small grains also can provide more ground cover.
Intercepting nitrates. Over 90% of nitrates is lost by water moving below the plant root zone through shallow groundwater before entering a tile line, Helmers says.
Enter prairie strips. “If the prairie root zone interacts with the shallow [groundwater] nitrate flow, we can get great nitrate reduction,” he says.
Ditto for saturated buffers, Helmers says. They intercept shallow groundwater flow and catch nitrates before water enters the tile line.
However, it’s not that simple. These practices add costs during tight margin times. They require increased management. In some cases, landowners would like to adopt them while tenants do not, and vice versa.
The good news is that abundant financial assistance from federal and state governments exists, Helmers says. “In some cases, cost-sharing reaches 100%,” he adds.
There also may be ways to increase payback, such as grazing cover crops. “There are long-term benefits to the soil system that may protect a long-term asset [land],” Helmers says.
The gradual adoption of cover crops — such as initially planting soybeans into them — can ease the transition. “Soybeans may respond more positively to cover crops with less risk of yield loss than in corn,” Helmers says.
The future
The good news is farmers have time to continue the strides they have made in improving water quality.
“We've seen an increase in the implementation of these practices,” Helmers says. “This has been coupled with an increase in infrastructure and technical assistance to boost farmer adoption. That needed to happen. Without assistance, these practices would not get installed and adopted in the right way.”
Continuing all of this, however, will require a long-term commitment and collective effort, he adds.
“Not every acre is conducive to the same practices,” Helmers says. “We have to think about those things as we scale up and try to make progress in the future. There's a need to accelerate the rate of adoption and reduce the risk of elevated nitrate concentrations.”