What are Growing Degree Days and How to Track Them?
Stop how you’re currently tracking and check out trackgdd.com
Growing Degree Days (GDD) — also known as Crop Heat Units — are a measure of effective thermal accumulation. This commonly known metric in agriculture circles can be an accurate predictor of tracking plant and pest growth as well as a key metric differentiating crop varieties.
But why is this important?
By adding GDD as a tool in your organization’s agricultural sciences toolkit, you can precisely time when to apply pest treatments, schedule harvests, and make data-driven decisions choosing the correct varieties for current and future climates.
So, if GDD is so great, why isn’t it at the heart of the agriculture supply chain? The lack of adoption breaks down into three main reasons:
- Recorded manually, GDD tracking is labor intensive
- With “Internet of Things” (IoT), GDD infrastructure can be costly
- Curated from a published source, GDD tracking is no longer timely
Manual GDD Tracking is Labor Intensive
There are multiple ways to calculate GDD; however, the de facto starting point is using the Daily Average method. The formula for a single day’s GDD is as follows:
The Daily Average method is simple, but limited. First, using the average daily temperature is more of an approximation than an accurate measure. Applying minimum/maximum cutoffs can help normalize the variance, but it’s still an educated guess at best. Second, in order to use GDD for proactive decision-making, the calculation must be done every day and the total accumulated GDD tracked.
While the math is easy when using the Daily Average, more advanced calculations that model calculating the area under the daily temperature curve become prohibitively complex from a mathematics perspective. Not to mention, the calculation still must be maintained on a daily basis.
“Internet of Things” GDD Tracking is Expensive
Smart agriculture — using connected hardware to create an IT data net — comes with significant costs that in many cases is cost-prohibitive, but even for those with the budget, the juice may not be worth the squeeze.
An IoT GDD solution would involve grid-connected temperature probes in every location that needs to be tracked. Connectivity becomes a major challenge for vast farms and fields in remote locations. Additionally, IT resources to manage the “smart” part of the solution come with their own price tag.
Simply put, an IoT GDD solution is expensive whether your currency is dollars or human expertise.
Published GDD Indexes are Outdated on Arrival
Certain regions, more so than others, have regularly published GDD indexes for each growing season. This has been the case in wine country for decades.
These published indexes require minimal effort as the data is synthesized and literally delivered to you; however, there are several deal-breaking shortcomings with this strategy.
First and foremost, published indexes are by definition a lagging indicator. While they are helpful for tracking long term trends, decisions in agriculture are often made years in advance. Adding in an extra year of lag dramatically reduces the ability to act upon the published data.
Another thing to consider is that indexes are generally published for a large region and as such the data is normalized across the area. This means that the data is less precise.
The Right Way to Track GDD
GDD is an excellent candidate for a lightweight, mobile-focused solution. Let the computers do the tracking and calculating while results are always at your fingertips.
One such option is an appropriately named app: Degree Days.
Degree Days is a newer entrant to the short list of online GDD tools, but its flexibility and ability to be used in integrations sets it apart from the others.
For quick one-off calculations, use the FREE online calculator on the homepage. You’ll get the total GDD for the date range along with a graph of the accumulation.
If you want more, sign up for an account and create an API key that can be used to query the Degree Days API and build your own tracking, reports, or visual aids.
How do you use growing degree days? What features do you want in a forward-looking digital tracker? Share your experiences below and the Degree Days team will be in touch!
