Grade Level: Middle School and High School

Growing Degree Days (At Home)

Overview

Do farmers make a random guess as to when to plant corn? NO! There’s a whole lot of science behind knowing when to plant corn, when to expect different stages of growth, and when to harvest – it’s called growing degree days (GDD). This activity requires some mathematical calculations to find out when is the optimum time to plant corn.

Activity

Take a look at the table below labeled, Growing Degree Days: An A”maize”ing Harvest Calculation. As you can see the temperature plays an important part in the growth of healthy corn. The formula for calculating the GDD is as follows. We are using F for Fahrenheit in this activity.

There are two rules to follow:

Rule 1: If the daily minimum temperature is (less than) < 50°F, set it equal to 50°F as the Lower Base Temperature in the equation. (For example, if the temperature is 38°F, we bump it up to 50°F in the
calculation.)
Rule 2: If the daily maximum temperature is (greater than) > 86°F, set it equal to 86°F in the equation. This is the Upper Limit Temperature.

Example:
If on a beautiful May day, the high (maximum temperature) was 80°F and the low (minimum temperature) was
56°F, then:

The average temperature for the day is = (80°F + 56°F) divided by / 2 = 68°F
And that day’s Corn GDD (°F) = 68°F – 50°F (this is the lower base temperature) = 18 GDD (°F)

Materials

Conclusion

Answer key to worksheets found in PDF.

Summary question. Most corn varieties require 100 GDDs to emerge. Based on your calculations would the corn in this example accumulate enough GDDs to emerge? Yes

This lesson is the work product of the Kansas Corn Commission. Our lessons are written in collaboration with Kansas teachers for use in the classroom. Teachers may copy and share this curriculum. Use of this product for commercial or promotional use is prohibited without express permission of Kansas Corn.