ISSUE #454 NDAWN Data Available For Improved Decision Making

454 NDAWN Data Available For Improved Decision Making


The North Dakota Agricultural Weather Network (NDAWN) is undoubtedly the most comprehensive and best source of weather data available to farmers anywhere in the world. What's even more remarkable is the data is available at no cost to sugarbeet growers and others. Dr. John Enz, NDSU Professor in the Soil Science Department and his staff of three make it all happen. This issue of Ag Notes will discuss possible ways to use the data to increase on-farm profit.

Using Growing Degree Day Data To Improve Weed Control

Predicting Early Sugarbeet Leaf Stages Using Growing Degree Days (GDD)

For most plants, physical development is strongly related to the accumulation of heat or temperature units above a threshold or base temperature below which little growth occurs. This lower threshold temperature will vary by plant species. In some plants there is also an upper threshold temperature above which little or no growth occurs. Although temperature is the most important factor controlling the rate of plant development, other factors such as water and light availability and day-length may modify its effects.

The most common temperature index used to estimate plant development is growing degree days (GDD) which are calculated from the daily maximum and minimum air temperature. Growing degree days have proven useful for scientists, crop consultants, and producers who use them to predict plant development rate and growth stage. In certain crops this information is used to help plan crop management decisions such as irrigation or pesticide application timing. Research by Caryle Holen, University of Minnesota, showed that early sugarbeet leaf development could be estimated quite accurately using accumulated GDD. Herbicide applications could then be based on GDD.

Sugarbeet Growing Degree Day Calculation

Growing degree days (GDD) are calculated by subtracting the plant's minimum threshold temperature from the average daily air temperature.

  • Daily Sugarbeet GDD (°F) = ((Daily Max Temp °F + Daily Min Temp °F) / 2) - 34°F.
  • A minimum threshold temperature of 34 °F and an upper threshold temperature of 86 °F are used for sugarbeets on the NDAWN web site.
  • Leaf stage predictions using GDD can now be acquired at by using the NDAWN link.

Weed Control Strategies Based on GDD

Sugarbeets are being planted fairly early again in 2004. In the 2002 and 2003 growing seasons early planted beet fields in many areas had four microrate applications applied by the 4-leaf stage. Growing conditions were cool, GDD were behind normal, and beet and weed growth was slowed. Data in figure 1 shows using a 7 day spray interval required 5 or even 6 microrate applications to maximize season long weed control. Many growers chose not to make the 5th or 6th microrate application or use a layby product resulting in some weedy fields in the Red River Valley. Using a 175 or 225 GDD spray schedule would result in more cost effective weed control, figure 1. Even if growers choose not to use GDD for herbicide application timing consider using it to compare to previous years GDD and lengthen spray intervals if it's cool, or if above normal for temperature, maybe shorten the spray interval a day or two. This can help maximize cost effective weed control.

Figure 1:


Data Available On NDAWN:

Kind of DataUse of Data
Air Temperature/GDD Herbicide timing, growth staging beets
Soil temperatures Seedbed preparation/planting
Root maggot emergence prediction
Timing of Amistar for rhizoctonia control
Wind speed/direction To spray or not to spray and potential of spray drift
Air temperature and relative humidity Cercospora leafspot development
Fall air and soil temperatures Harvest and defoliation practices

How to Access NDAWN Data:

  • Go to
  • On our site go to Pest Alert then click on the following links: Cercospora Daily Infection Values, Predictive Leaf Stages & Growing Degree Days

Coming Soon! - New Ag Systems

Shareholder sugar reports and the other information on your shareholder entities will soon have a new look and feel. This new system will have friendlier navigation and provide easier selection of your Shareholder Entities within your Master ID. If you have not created a Master ID please do so now. A Master ID is now required to run your reports from within Ag systems. See the instructions in the Shareholder Info section of web site. If you need assistance, please contact the Ag Office Coordinator in your factory district.