U of I, USDA collaborate on crop nitrogen calculator, new barley nitrogen guidelines

MOSCOW, Idaho — University of Idaho and U.S. Department of Agriculture researchers have developed a free online calculator to help Idaho barley and sugar beet growers determine how much nitrogen fertilizer to apply for the greatest profit.

The researchers plan to expand the tool in the future to provide customized nitrogen recommendations for additional Idaho crops. Using data collected during the project, the team has also updated Idaho’s nitrogen application guidelines for malt barley.

The calculator and updated guidelines are available at idahocropnitrogen.org.

Jared Spackman, a U of I associate professor and Extension specialist and the Idaho Barley Commission Endowed Barley Agronomist, and Christopher Rogers, a research soil scientist with USDA’s Agricultural Research Service (ARS) in Kimberly, led the crop research. UI Extension agricultural economist Patrick Hatzenbuehler led the project’s economic analysis.

Users enter information about their crop variety, existing soil nitrogen levels, yield goals, commodity prices, fertilizer type and fertilizer costs. The calculator then estimates both the nitrogen rate needed to achieve maximum yield and the rate likely to produce the greatest profit. Applying more fertilizer can eventually cost more than the additional crop yield is worth.

“It’s really helping farmers make better on-farm decisions for their bottom line,” Rogers said. “Just achieving the maximum yield may not be the most profitable for them.”

The team launched the calculator in early July and plans to refine it by February, in time to help growers plan their fertilizer purchases.

The calculator’s estimates for irrigated spring barley and the recently updated nitrogen guidelines for malt barley are based on field trials conducted at research plots spanning from Twin Falls to Tetonia. The tool currently includes barley data from 2015 through 2023 and will be updated regularly. The team plans to add data from trials conducted through 2026 by February 2027.

Idaho is the nation’s No. 1 barley-producing state and accounts for 40% of U.S. barley production.

Idaho’s nitrogen guidelines for malt barley were last updated in 2003.

Rogers led barley nitrogen trials while working at U of I from 2015-18 and in 2019 while with ARS. Spackman has spearheaded the trials since 2020.

Several stakeholders have helped support the work. ARS contributed $176,000 toward salary and travel expenses of Hatzenbuehler’s postdoctoral researcher, Chanchal Pramanik, who developed underlying economic equations and a prototype of the calculator. UI Extension contributed an approximately $5,000 Innovative Projects grant for U of I Research Computing and Data Services to build a public-facing website that hosts the tool. The Idaho Barley Commission (IBC) contributed $17,000 to refine the tool based on user feedback during the next year. IBC also provided funding for barley nitrogen trials.

David Tarkalson, an ARS research soil scientist based in Kimberly, conducted the trials that supplied the sugar beet data used in the calculator. The researchers also have extensive data from Idaho nitrogen trials of mustard, forage grasses, winter barley and several classes of wheat.

“The best thing about this tool is that it allows all of the field trial data to be accessed easily through the website,” Hatzenbuehler said.

U of I and USDA have shared the tool with IBC and promoted it at recent cereal research field days. They plan to promote it during upcoming industry conventions and meetings.

“There has been a fair bit of interest from growers as they hear about the project and what we’re doing,” Spackman said.

Among those interested is Idaho Falls farmer Mar Thiel, ’92, who has hosted university cereal trials on his farm for 27 years. Thiel plans to test the calculator’s recommendations on limited acreage before expanding its use.

Although he routinely uses soil and in-season petiole testing to guide nitrogen applications for higher-value crops such as potatoes, he has generally applied a standard nitrogen rate across his barley acres.

“I think it would be great to have some updated data, especially when you can access it online,” Thiel said. “The more information, the better.”

Media contact

Jared Spackman
Associate professor, Extension specialist, Idaho Barley Commission endowed barley agronomist
208-844-6323
jspackman@uidaho.edu