By Dennis Todey and Laura Edwards
As South Dakota reaches the main heat accumulation period of the growing season, the accumulation of Growing Degree Days (GDD) becomes something to be watched for here and across the Corn Belt. Because of the differences in varieties, planting dates, and locations, overall tracking of specific crop progress can be a little difficult. So far this year GDD accumulation is close to average overall except for locations in the southeast where totals are a few days ahead of average.
GDD Decision Support Tool
Tracking your local conditions online for your own corn crop is now much easier thanks to a growing degree day tool that can help estimate when your corn crop will reach critical growth stages. The free tool, called Corn GDD DST (Decision Support Tool), was developed as part of a USDA NIFA project with staff from South Dakota State University. The Corn GDD DST accumulates GDDs using local temperature information from across the Corn Belt to track current conditions. The current accumulation, updated daily, compares to historical averages or other recent individual years to provide different historical comparisons.
Using the Tool
The online tool allows you to select your location, planting date, crop maturity, years you would like to use for comparison, and graph display options. The tool will show a graph that includes likely dates for silking and black layer for the current growing season. Using climatology and long-term averages, an estimate is shown on when the crop will reach these critical growth stages. The website runs quickly which allows you to compare many scenarios. You can also download the data to review the numbers behind the graphs. Some ways you can use this for decision-making are: potential for your existing crop reaching maturity before freeze dates, deciding on crop maturity options if replant is necessary, and future planning for potential variety choices. In the near future, the tool will include a forecast GDD based on computer models and not just a climatological projection. The tool works via web site, but is programmed to work very well on mobile devices.
Reading Results
Figure 1. Growing degree day data for Davison County, SD.
The graphic above shows the data for Davison County, SD as of June 16 with a planting date of April 19 for a 103 day variety. The vertical blue lines indicate historical fall frost dates. The taller lines have been more common than the shorter lines. The shaded areas show the historical range of accumulated GDD during the growing season.
Click here to see more...