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Nitrogen use efficiency at the ground level

Article cover photo
Iowa Soybean Association researchers were recently involved in a pilot study looking a nitrogen balance as an efficiency metric. (Photo: Joseph L. Murphy/Iowa Soybean Association)

By Carol Brown, ISA environmental communications specialist

Two Iowa Soybean Association (ISA) researchers were involved in a small pilot study last fall that has the potential to expand into further studies.

What sounds like a dramatic movie title, the “N Balance project” is an exploratory mission led by the Washington D.C.-based Environmental Defense Fund (EDF). Founded in 1967, EDF is a national nonprofit organization advocating for lasting solutions to environmental issues.

ISA Director of Analytics Peter Kyveryga and Chris Hay, ISA senior environmental scientist, conducted data analyses for EDF to see if nitrogen (N) balance could become a sustainability and efficiency metric for farmers, which could in turn, be useful for the food supply chain.

What is N Balance?

“At the simplest level, if you take the total nitrogen applied to a field, subtract what was removed by the crop, what is left is N Balance,” said Kyveryga. “The EDF arrived at a sweet spot, or safe operating space, for nitrogen fertilization. If the N balance is too low, then soil organic matter gets mined. If the estimated balance is too high, nitrogen fertilization is not efficient.”

In Iowa, and agriculture in general, there are many variables that can affect the N balance such as soil, weather, inputs, nitrogen fixation and more. But Hay and Kyveryga approached the study at the basic level, using only field management data, fall cornstalk nitrate test surveys, water monitoring data and yields from farms in 2016 and 2017, to evaluate N Balance for each location.

“N Balance could be used as another benchmarking tool for farmers to gauge nitrogen usage,” said Hay. “If I’m a farmer, I could look at my N balance relative to other farmers in the area, under similar conditions, and compare how I’m doing.”

ISA’s involvement

In the fall of 2017, Hay and Kyvergya were invited to an EDF meeting to discuss the pursuit of N Balance. They met with EDF staff and representatives from universities and organizations in other states, said Hay, to talk through the idea.

“ISA is somewhat unique in that we have agronomic, yield and fertilizer information, but we also have water quality monitoring data as well,” said Hay. “ISA is a good test case for the N Balance concept.”

They met recently in Waterloo with Jason Gomes, project coordinator for the Middle Cedar Partnership Project (MCPP), and a small group of farmers to share N Balance reports. Gomes has been working with the farmers on water quality improvement in the watershed.

“All the growers at the meeting have been working with ISA either on strip trials or through the MCPP,” said Gomes. “It’s hard for growers to improve on something they don’t systematically measure. N Balance and other nitrogen use efficiency measures give them some context for understanding how different fertilizer management practices work to improve or worsen environmental nitrogen losses.”

Through the reports, the farmers could see how they compared with their neighbors, anonymously, in northeast Iowa. Hay said this meeting was used to gauge farmer reactions to the shared data. He and Kyveryga will meet with EDF soon to share results from the reports and the meeting.

Hay thinks that farmers could use N Balance as one way to read nitrogen use efficiency on the farm. But a more in-depth study needs to take place, especially in Iowa, to factor in the nitrogen-rich soils and the production variables.  

“Nitrogen rate by itself isn’t very useful to measure efficiency. There are many factors that affect yield, which is one of the reasons ISA conducts strip trials,” agreed Kyveryga.

Gomes echoed Kyveryga’s comments. “From an environmental standpoint, it’s critical for ISA and growers to continue to develop and refine tools for measuring nitrogen usage.”

EDF is working with partners to explore N balance in other states. The study results, along with potential future efforts in Iowa with ISA, will help determine the value of N Balance for benchmarking nitrogen use efficiency and improvements in environmental performance.

Contact Carol Brown at:






For media inquiries, permission to republish articles or to request high-res photos, please contact Katie James, ISA Public Relations Manager at © 2020 Iowa Soybean Association. All rights reserved.

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