Online Tool Helps Farmers with Nitrogen Application Decisions

Chad Hart portrait
Chad Hart

AMES, Iowa — A federally funded climate initiative, that includes Iowa State University, has launched a new online decision support tool to help farmers and farm advisers manage the application of in-field nitrogen for maximizing crop yields and minimizing environmental damage.

The free tool, called “Corn Split N,” is available for use in Iowa, Illinois, Indiana, Missouri and Kansas. Corn Split N combines historical weather data and fieldwork conditions with economic considerations to determine the feasibility and profitability of completing a post-planting nitrogen application for corn production.

The tool was developed as part of “Useful to Usable,” or U2U, a USDA National Institute for Food and Agriculture-funded research and extension project designed to improve the resilience and profitability of farms in the Corn Belt amid a variable and changing climate. The project team includes 50 faculty, staff and students from nine north-central universities with expertise in applied climatology, crop modeling, agronomy, cybertechnology, agricultural economics and other social sciences.

Chad Hart, an Iowa State associate professor of economics and extension crop markets specialist, is the local project coordinator for the Corn Split N tool.

“Traditionally, farmers have applied nitrogen to the soil in a single pass either in the fall or in the spring before planting,” Hart said. “However, research has shown that by splitting the nitrogen over two intervals, applying it once in the fall or spring when the soil is not saturated and the temperature is between 50 and 32 degrees Fahrenheit, and then a second time when the plants are in the ground and in most need of it, will ultimately lead to better results. Less fertilizer will be needed overall and not as much will be lost in run off.”

Hart said that nitrogen management of corn includes many factors. One is the timing of the application, which varies depending on weather and soil conditions. Corn Split N tool’s historical climate data is designed to assist farmers pinpoint when nitrogen should be applied for best results.

Because the post-planting application must be done before the corn gets too tall, estimates of corn development stages based on location, selected planting date and the accumulated corn growing degree days for the year also are factored into the tool. Growing degree day accumulations and associated corn growth beyond the current day are estimated based on the historical 30-year (1981 to 2010) average degree day accumulation for a location.

Hart said the Corn Split N tool helps farmers quantify the costs and benefits under average, worst and best case scenarios when doing a post-planting nitrogen application, even taking into account two passes of ground equipment in the fields.

Farmers get customized results based on their planting and fertilization schedule, local costs and available equipment. A summarized fieldwork table and crop calendar also allow farmers to see how schedule adjustments might affect their ability to fertilize on time.

In 2015, the product will be expanded to seven additional north-central states: Wisconsin, Minnesota, South Dakota, North Dakota, Nebraska, Ohio and Michigan.

To learn more, visit or the U2U homepage,

U2U project partners are Purdue University, Iowa State, Michigan State University, South Dakota State University, University of Illinois, University of Michigan, University of Missouri, University of Nebraska, University of Wisconsin, High Plains and Midwestern NOAA Regional Climate Centers and the National Drought Mitigation Center. Linda Stalker Prokopy at Purdue is the U2U project director.

Corn Split N is part of the U2U suite of tools created to help farmers and agricultural advisers manage increasingly variable weather and climate conditions across the Corn Belt. The tools incorporate historical climate data to help inform purchasing, marketing and activity planning throughout the growing cycle. Data in all tools are updated on a regular basis, even daily in some cases.

Other U2U decision support tools include:

  • AgClimate View provides convenient access to customized historical climate and crop yield data for the U.S. Corn Belt. Users can view graphs of monthly temperature and precipitation, plot corn and soybean yield trends, and compare climate and yields over the past 30 years.
  • Corn Growing Degree Day allows users to track real-time and historical accumulations, assess spring and fall frost risk and guide decisions related to planting, harvest and seed selection. This innovative tool integrates corn development stages with weather and climate data for location-specific decision support tailored specifically to agricultural production.
  • Climate Patterns Viewer helps farmers and agricultural advisers assess how climate patterns in other parts of the world can influence local climate conditions and corn yields across the Corn Belt. The tool can help growers make more informed farm management decisions during different phases of the El Niño Southern Oscillation and Arctic Oscillation by relating historical events to associated precipitation and temperature impacts over the course of a year.