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Nutrient Science

Growing Degree Days Calculator: Benefits & Use

eKonomics News Team

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eKonomics’ Growing Degree Days (GDD) calculator is a powerful tool built to help growers determine plant and pest development rates based on their geographical location. The weather-based GDD calculation is used to measure heat accumulation (above a specific threshold) and help predict a variety of things including the approximate date the crop will reach maturity.

Use the GDD Calculator Tool

Growing Degree Days Calculator Tool Button

Benefits of Using the GDD Calculator Tool

Different crops require different exposure amounts of GDDs or heat units to complete their lifecycle. For some crops, like corn and soybeans, one can actually use GDDs to determine where a crop is in its development cycle. This information can be useful for calculating where crops are in their growth stage and help determine the optimum time for crop scouting.

In addition, GDDs can be used for a variety of things including:

  • Assessing the suitability of a region for production of a particular crop
  • Estimating the growth stages of crops, weeds or even life stages of insects
  • Predicting maturity and cutting dates of forage crops
  • Predicting the best time to apply fertilizers or pesticides
  • Estimating the heat stress on crops
  • Planning the spacing of planting dates to produce separate harvest dates

Skip to 1:27 on the video to reach the GDD section.

How to Use the GDD Calculator Tool

Growing degrees are calculated each day as maximum temperature plus the minimum temperature divided by two (or the mean temperature), minus the base temperature.

GDDs are accumulated by adding each day’s growing degrees influence as the season continues. If the average temperature is below the base temperature, the growing degree day value for that day is zero.

GDD Calc tutorial image

1) Location selector: enter your postal/ zip code, state/province, or address. If your area does not work, select the geographical location nearest you.

2) Crop or pest selector: choose your crop or pest to get started.

3) Start date: enter your start date. Ensure your end date does not exceed seven months from the time selected.

4) End date: enter your end date. Ensure this date does not exceed seven months from the start date.

General Rules of Thumb

Using corn as an example, the growing degree threshold is 50 degrees Fahrenheit (10 o Celsius).

corn low GDD

If your average air temperature for one day is 51o degrees Fahrenheit (10.5 o Celsius) that means you have accumulated 1 GDD for that day.

corn high GDD

Or, if your average air temperature is 80 o F (26.5 o C) that means you have accumulated 30 GDDs.

The GDD tools calculated answer will help predict where a crop will be in its life cycle, vegetative stages, and when you need to be in the field scouting for problems.

Going Beyond the Basics

Unless crops are stressed by other environmental factors like moisture, the development rate to maturity for many plants depends upon the daily air temperature. Because many developmental events of plants and insects depend on the accumulation of specific quantities of heat, it is possible to predict when these events should occur during a growing season regardless of differences in temperatures from year to year.

When it comes to pest control, GDDs can be used to determine pest development and life stage. This allows farmers the ability to implement their pest control methods when the pest is at its most vulnerable state, increasing effectiveness.

Go to the GDD Calculator Tool

Growing Degree Days Calculator Tool Button

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