Soybean Research

Weed management in soybean
 Dr. Peter Sikkema; University of Guelph, Ridgetown Campus

A total of 18 field experiments were conducted on weed management in Roundup Ready (RR) and Identity Preserved (IP) soybeans. Field studies were established at the Huron Research Station and the University of Guelph, Ridgetown Campus.

A summary of the results are as follows:

1. One early post-emergence application of glyphosate provides excellent weed control and optimal yields in RR soybean.
2. The late post-emergence application of Pursuit, Classic, Pinnacle and FirstRate cause unacceptable visible crop injury in soybean and a decrease in height. The late application of Pursuit and Pinnacle resulted in a decrease in yield. The late application of Roundup, Reflex, Basagran and Assure did not result in significant injury and no decrease in height or yield of soybean.
3. Glyphosate provides the best weed control and soybean yield is maximized when sprayed between 9:00 am and 6:00 pm.
4. The efficacy of glyphosate is reduced when tankmixed with some formulations of manganese.
5. There is a trend to reduced soybean vigour and yield when the burndown is delayed.
6. There was no injury in RR soybean when glyphosate was tankmixed with either an insecticide or fungicide. Overall, there was no detrimental effect on weed control and there was no difference in soybean yield. Interestingly, the addition of the fungicides increased soybean yield an average of one bushel per acre.