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SoyStage: An online tool for predicting soybean development

Ginger Rowsey Soybeans.jpeg
A new website developed by University of Arkansas System Division of Agriculture can help farmers predict soybean development based on location and maturity group.
Site predicts key soybean development stages for Midsouth farms.

Midsouth soybean growers have a new management tool at their disposal. An interactive website called SoyStage uses weather data to predict soybean development based on emergence date, maturity group, and location. The site was developed by the University of Arkansas System Division of Agriculture. 

“A lot of management decisions depend upon development stages,” said Larry Purcell, Distinguished Professor and Altheimer Chair for Soybean Research with the University of Arkansas. “For example, you want to make sure you’re irrigating during seedfill. This site can give you a very good idea of when seedfill would begin. Timing insecticide applications or coordinating labor for end of season activities are other examples of how the information at this site can be helpful.” 

Purcell worked with former graduate student, Caio dos Santos and former post-doctoral associate Montserrat Salmeron, to create SoyStage. The developmental stage prediction tool is the result of a three-year study to determine the temperature and photoperiod responses of soybean maturity groups commonly grown in the Midsouth. This is the first full season the site has been publicly available.  

How to use 

The SoyStage website is easy to use and allows growers to see developmental stage predictions based on historical weather data or current year weather data. Simply enter your zip code, emergence date and select a maturity group from a drop-down menu (the options range from MG 3.2 – MG 6.7). The site offers predictions for developmental stages for first flower (R1), beginning seedfill (R5) and physiological maturity (R7). Harvest maturity (R8) typically occurs a week after the predicted date for R7. 

Purcell says it is important to note that predictions are based upon emergence dates and not planting dates, as the time between planting and emergence may be as few as four days under optimum conditions, or as many as 14 days or more when the soil is dry and cold. If your emergence date has a freeze risk, the site will indicate that.  


SoyStage offers two ways to view soybean development predictions. A map view (pictured) allows uses to scroll over their location to see anticipated dates or R1, R5 or R7 stages. Visitors can also see a graph view of predictions for all three developmental stages specific to their zip code.

Using 35 years of historical weather data from nearly 2,800 locations across the region, Purcell has found SoyStage predictions to be very accurate and says his team has received positive feedback from farmers who have tested the site. 

“The predicted dates of R1, R5 and R7 from SoyStage agree very closely with the observed dates from the original field experiments,” Purcell said. “Of course, you still want to go out to the field, but this site gives you a good idea of when to go out in the field to check.” 

The average differences between the predicted dates and observed dates were within the same day for R1, 1.10 days for R5 and 3.7 days for R7. 

“Farmers are constantly on the go and anything that can help them plan their application timings could be helpful,” Purcell said. “Hopefully, this is another tool they’ll find useful in their daily management decisions.” 

Development of SoyStage was funded by the United Soybean Board and the Midsouth Soybean Board. 

TAGS: Technology
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