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Overview

Growing Degree Days (GDD)​

Growing Degree Days (GDD), also called Growing Degree Units (GDU), is a weather-based indicator for assessing crop development. GDD measures heat accumulation to predict plant and pest development rates such as the date that a crop reaches maturity.

GDD Calculation​

GDD accumulation is most often measured from the planting date until the current date, with a maximum range of up to 180 days (about 6 months). The standard equation to calculate daily GDDs is:

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Where Tmax is the maximum recorded daily temperature and Tmin is the minimum recorded daily temperature. Tmax and Tmin are clipped with a crop-specific upper cutoff temperature and lower base temperature (Tbase) where development of the plant occurs. Any negative value from this daily calculation is set to 0.

For example, the threshold for corn in most regions are Tbase = 10°C and an upper cutoff of 30°C. Hence, if the maximum daily temperature reaches 32°C, Tmax will be clipped to 30°C, as no plant development will occur between 30-32°C. Similarly, if the minimum daily temperature is 8°C, Tmin will be clipped to 10°C, as no plant development will occur between 8-10°C. The clipped values are then used in the equation above to estimate the accumulated number of GDDs per day.

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Example of how the GDD output can be used, to estimate corn phenological stage

GDD APS​

The GDD APS uses location, planting date (to begin the GDD accumulation), crop type, and end date (on or before the current date), to estimate the amount of growing degree days that have accumulated.

Crops Supported by the GDD APS​

The Bayer AgPowered GDD Calculation Service currently supports following crops: CORN, SOYBEAN, WINTER_WHEAT, CANOLA, COTTON, SUGAR_BEET

Regions Supported by the GDD APS​

The GDD APS is supported in multiple regions across the world. The following map depicts coverage with the highlighted areas.

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Supported regions for GDD calculations based on available weather data.

Historical Growing Seasons Supported by GDD APS​

The GDD APS has weather data available from January 1st, 2020 and can be used to calculate GDD values for locations with planting dates after this date.

Install GDD APS

To install the GDD APS, start here.