Wind Analysis Tool for Predicting Pollen Drift • 7.17.17

Chuck Hill - AgriGold Specialty Products Manager

Wind Analysis Tool for Predicting Pollen Drift

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Growers of non-gmo corn, white corn, and waxy corn have struggled for years to predict where unwanted pollen might come from.  Now growers of IP yellow and white corn near fields of Enogen® corn are doing this as well.  Most pollen falls in the field it came from.  Yet, with only a 15-mph wind, pollen can travel as far as ½ mile within a couple of minutes while it is still viable (Nielsen, 2016). After discussing this challenge with Dr. Mark Westgate, Iowa State Professor of Agronomy, he directed me to a website developed by a fellow ISU professor, Daryl Herzmann.  The website shows detailed information of wind speed, direction, and duration in a diagram called a Wind Rose.

This article will help guide you through using the website so you can develop a wind rose for your fields.  The wind data comes from airports around the Midwest.  You will be able to choose the location you use.    

Gather Information

Before going to the website, it is helpful to gather some information.  First map out where the fields you are concerned about, I call them the “target” fields, are located.  You will have hybrid and planting date information on those fields.  You will need information on what corn is planted near your target fields.  You will want to know what hybrids and when they were planted.  You need to go at least ½ mile away on all sides of the target field.  Don’t assume the wind only comes from the south or west in the summer.

Calculating Pollination Window

Once you have the hybrid and planting information you will need to calculate silk emergence in your target field.  This can be estimated by using Growing Degree Unit (GDU) data and the data from your hybrid profile for GDUs to Mid-Pollen.  GDU data can be calculated from several websites/apps or gotten from Advantage Acre® if you are a subscriber.   For example, A6499 is 1362 GDUs to Mid-Pollen from the AgriGold Hybrid Profile Guide.  Using the Advantage Acre timeline, I can find what date that occurred on.  If you use a GDU calculator you can estimate that date as well.  Pollen shed is normally a two-week process, so go one week to both sides of the mid-pollen date to determine your silk exposure window.  If your corn field had uneven emergence and/or replant you may want to widen that window.

You have now determined the time period you are concerned about the wind.  However, if you want to refine your time period you can add the information about the surrounding fields.  By going through the same process, you can determine the pollen shed windows for those fields.  Then you can overlap the pollination windows to possibly narrow the time period you are concerned about.  Offsetting planting dates is a good away to lessen the risk of cross pollination.

Now you are ready to go to the website.  The directions will walk you through step-by-step on how to use it.

IEM Site

This example is for the AgriGold office near Lawrenceville, IL for a period last summer. (Click on image 4).

Select By Network – From drop down select “state” ASOS.  If in Iowa Select “Iowa AWOS”  Click “Switch Network” button.

Select By Station – Select nearest location to your target field from map or drop down list.  Click “Select Station” button. (Click on image 5).

Click on “*Custom Wind Roses” tab. (Click on image 6).

Select Start/End Time:

Start:     Select Year, Month, Day, Hour (Beginning date of your calculated time period)
End:       Select Year, Month, Day, Hour (Ending date of you calculated time period)

Check box by #3. Limit to Range of hours given by start and end time.  Pollen usually sheds in the morning to early afternoon.  Try using 8:00 AM to 2:00 PM.

Direction Bins: Change to 24.  You can experiment with this.  Fewer bins consolidates wind the readings.

Image Format: Change to Portable Document Format (>PDF).  This will make Wind Rose easier to print.

Click “Submit” button.  Wind Rose will generate after a brief moment. (Click on image 7).

Interpreting your Wind Rose

  • Imagine your target field as the center point of the wind rose.  The wind is blowing in to the center.
  • Each triangle represents a wind direction during the designated time period.
  • Wind speed is designated by color key at the bottom.
  • Wind direction is designated on the outside perimeter.
  • Frequency (%) of speed and direction is designated by the concentric circles.  Each wind rose may have different frequency scale.

Example: The red circled triangle tells us there was a period of wind from the NNE approximately 9% of the time period.  Approximately 5% of the time period the wind was NNE at 20+ mph.  Approximately 1.5% of the time period the wind was NNE at 15-20 mph.  The remaining 2.5% of the time period the wind was NNE at 10-15 mph.  This adds up to the 9%.

How can you use this information to help you lessen the risk from contamination causing the corn to be rejected and not qualifying for a premium?  Hopefully now you have a clearer picture of what parts of your target fields have possible issues.  Standard harvest procedure for IP corn fields is to harvest border rows all the way around the field and store separate from your IP corn.  If your isolation distance is less than 165 feet, the recommendation is to harvest 16 border rows.  If the isolation distance is between 165 feet and 660 feet, the recommendation is to harvest 8 rows (Thomison and Geyer, 2016).  The wind rose could help you modify border row harvest to reflect possible risk areas.  I recommend harvesting a minimum of 8 rows whether there is any perceived risk or not.

For those who have their own weather stations with recordable wind information there may be an option to use that with a different website or software.  I am currently working on that with a wind logger at a field near me.  When I get that figured out I will put out another article.

I hope this information can help lessen the risk of mixing contaminated corn with your IP corn.  If you have questions about this article, please contact me.  If you have questions about the website you can contact Daryl Herzmann at ISU.  Our contact information is below.

Chuck Hill - AgriGold - Specialty Products Manager,, 217.473.6063, Twitter @agold_chuck

Daryl Herzmann - Iowa State University - Analyst,, 515.294.5978

Enogen® is a registered trademark of Syngenta Seeds, Inc.

Advantage Acre® is a registered trademark of AgReliant Genetics LLC
Nielsen, Bob. 2016. Tassel Emergence & Pollen Shed.  Purdue University
Peter Thomison and Allen Geyer. 2016. Managing “Pollen Drift” to Minimize Contamination of Non-GMO Corn.  The Ohio State University

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Wind Logger

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Near AgriGold office in Lawrenceville, IL for a period last summer

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Wind Rose Plot

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