Growing Degree Days Accumulations for Corn under Spring and Fall Freeze Risks - UNL CropWatch
December 20, 2012
Knowing average spring and fall freeze dates and average accumulated growing degree days for your area can help you manage risk when selecting seed and setting planting dates.
Growing degree days (GDD) are an important measure to track growth and development of corn. Since GDD are based on temperature, the total number of GDDs accumulated during a growing season may vary considerably from one location to another.
Other critically important criterion to consider are spring and fall freeze risks. Average GDD accumulations under various freeze risk scenarios provide useful information for corn producers selecting an appropriate corn hybrid along with planting and harvest dates for corn. For this analysis, GDD accumulations were calculated based on a 86/50 range, with understanding that corn does not grow when the temperature is above 86oF or below 50°F.
Tables 1-3 summarize GDD accumulations under three spring and fall freeze risks scenarios — low, medium, and high.
- Low freeze risk corresponds to a 10% chance of freeze impacting corn in spring/fall.
- Medium freeze risk corresponds to a 50% chance of freeze impacting corn in spring/fall.
- High freeze risk corresponds to a 90% chance of freeze impacting corn in spring/fall.
Referring to Table 1, there is a low risk (1 in 10 years) of spring freeze occurring after May 9 and fall freeze occurring before September 22 in Lincoln. In the low freeze-risk category, the average number of GDD accumulated in Lincoln is 3182. So, even under the more conservative freeze risk scenario, longer season hybrids are viable for Lincoln.
Table 3 shows a different outlook for Scottsbluff, which lies in a different climate zone. Scottsbluff only accumulated 2219 GDD under the low freeze risk scenario. So, for instance, if you wanted to plant a 2400 GDD corn variety in Scottsbluff, you would assume a medium to high risk of freeze.
Please note that this summarized data is based on 30-year averages. When assessing current trends and making decisions for your operation, also consider year-to-year climate variability.
Extension Educator in Climate Variability
Table 1. GDD accumulations under spring and fall freeze risks for Lincoln.
Table 2. GDD accumulations under spring and fall freeze risks for Norfolk.
Table 3. GDD accumulations under spring and fall freeze risks for Scottsbluff.