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Angie Peltier

Angie Peltier
Former Extension Educator, Commercial Agriculture

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Hill and Furrow

Current topics about crop production in Western Illinois, including field crops research at the NWIARDC in Monmouth.
Figure. Corn Growing Degree Day decision support tool. After a location is selected, the tool can be further customized to include planting date and hybrid-specific information regarding phenological milestones (see blue box). (Credits: U2U Project:

Free Corn Growing Degree Day (GDD) Decision Support Tool

Through funding provided by the USDA-National Institute of Food and Agriculture, a group of researchers from nine different Midwestern states and Universities worked collaboratively to develop a series of decision support tools for Midwestern crop producers. One of these is called the Corn Growing Degree Day (GDD) decision support tool.

Corn plants require heat (between 50 and 86 °F) in order to grow, develop and reach vegetative and reproductive milestones on their way to physiological maturity. Growing degree days are a measure of the accumulated heat and associated corn growth and development during the growing season. Chapter 2 in the Illinois Agronomy Handbook has a good description of daily GDD calculations and the number of GDD that typically must accumulate in order for corn to reach specific growth stages.

The Corn Growing Degree decision support tool allows corn producers to access location-specific historical (1981-2010) and current growing degree day projections and how they will likely influence crop growth and development. Producers are able to select their location, and customize the tool based on their actual planting date and information that is specific to the hybrid that they planted – including days to maturity, GDDs to silking and/or GDDs to black layer (Figure – see blue box).

Based on both historical weather data and current weather projections, the tool then creates a graph that highlights spring and fall frost dates, and date ranges for the historical and predicted current-year crop-critical phenological milestones of silking and black layer (Figure).

The tool can be of use in multiple scenarios, including but not limited to the following:

1) Producers can compare projected developmental milestones among different 2015 planting dates and/or different 2015 hybrid maturities.

2) Producers can compare projected 2015 crop development to years in the recent past (1981-2010).

3) Producers can gauge when frost risk is highest. This can be important in the spring when producers are thinking about planting. It can also be important when planting is delayed in the spring time and producers are worried about a crop reaching physiological maturity before a fall frost.

Additional Resources

Corn Growing Degree Day (GDD) Decision Support Tool

Illinois Agronomy Handbook - Chapter 2: Corn - By. Dr. Emerson Nafziger

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