Pioneer GDU (Growing Degree Unit) Calculator
Calculation Results
Daily GDU Accumulation:
0
Understanding the Pioneer GDU Calculation
In corn production, physiological time is measured by Growing Degree Units (GDUs), not by calendar days. Because corn development is highly dependent on temperature, tracking GDUs allows farmers to predict when a crop will reach specific growth stages like silking (R1) or physiological maturity (black layer/R6).
The Standard GDU Formula
The "Modified 86/50 Method" is the industry standard for calculating corn GDUs. This method accounts for the fact that corn growth slows down when temperatures exceed 86°F or fall below 50°F.
GDU = [(Daily Max Temp + Daily Min Temp) / 2] – Base Temp
The Rules of Adjustment
- Upper Limit: If the daily maximum temperature is higher than 86°F, it is set to 86°F for the calculation. This is because corn growth does not increase significantly above this threshold.
- Lower Limit: If the daily minimum temperature is lower than 50°F, it is set to 50°F. This represents the point where growth effectively stops.
- Base Temperature: The standard base temperature for corn is 50°F.
Example Calculation
Suppose you have a hot summer day with a high of 92°F and a low of 68°F:
- Adjust Max Temp: 92°F becomes 86°F.
- Adjust Min Temp: 68°F remains 68°F.
- Calculate Average: (86 + 68) / 2 = 77.
- Subtract Base: 77 – 50 = 27 GDUs for that day.
Why Track GDUs?
Tracking accumulated GDUs from the date of planting helps in various management decisions:
- Hybrid Selection: Choose hybrids with GDU ratings that fit your local growing season length.
- Scouting: Predict when corn will reach critical stages like V5 (side-dressing nitrogen) or R1 (applying fungicides).
- Harvest Planning: Estimate when the crop will reach maturity to prepare equipment and storage.