Growing Degree Days Accumulations for Corn under Spring and Fall Freeze Risks - UNL CropWatch

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.

Tapan Pathak
Extension Educator in Climate Variability

Table 1. GDD accumulations under spring and fall freeze risks for Lincoln.

 

 

GDD Accumulations

Lincoln

 

Low Risk of
Fall Freeze

Medium Risk of
Fall Freeze

High Risk of
Fall Freeze

 

 

Sept. 22

Oct. 5

Oct. 19

Low Risk of Spring Freeze

May 9

2920

3092

3222

Medium Risk of Spring Freeze

Apr 25

3074

3237

3367

High Risk of Spring Freeze

Apr 12

3182

3353

3483

 

Table 2. GDD accumulations under spring and fall freeze risks for Norfolk.

 

 

GDD Accumulations

Norfolk

 

Low Risk of
Fall Freeze

Medium Risk of
Fall Freeze

High Risk of
Fall Freeze

 

 

Sept. 19

Oct. 4

Oct. 18

Low Risk of Spring Freeze

May 11

2656

2835

Not Available

Medium Risk of Spring Freeze

Apr 27

2794

2973

3092

High Risk of Spring Freeze

Apr 13

2910

3089

3214

 

Table 3. GDD accumulations under spring and fall freeze risks for Scottsbluff.

 

 

GDD Accumulations

Scottsbluff

 

Low Risk of
Fall Freeze

Medium Risk of
Fall Freeze

High Risk of
Fall Fr
eeze

 

 

Sept.  17

Sept. 29

Oct. 11

Low Risk of Spring Freeze

May 22

2219

2364

2479

Medium Risk of Spring Freeze

May 8

2378

2522

2637

High Risk of Spring Freeze

Apr 23

2499

2643

2758