Grower Resource: Glyphosate Labels, Soy Flowers and Wheel-Track Damage

Here’s a handy update from UW-Extension Soybean Specialist Dr. Shawn Conley covering glyphosate labels, soybean flowers and wheel-track damage.

The good doctor makes three important points.

  1. At this stage of the growing season, many soybean fields reach the R1 stage and begin to flower. Soybeans typically flower for three to five weeks, depending on the environment and when the seeds went into the ground. During this short window, soybeans will abort “anywhere from 20 to 80%” of the flowers they produce. Generally speaking, the first and last flush of flowers are the most likely to be aborted.
  2. Speaking of short windows, the timing for glyphosate application in early planted fields is coming up fast. The glyphosate labels indicate you can apply through “R2 or full flower.” Dr. Conley notes it takes four days on average to  move from R1 (beginning flower) to R2 (full flower), and 10 days to go from R2 to the start of R3 (beginning pod). Just a friendly reminder: Applications made in the R3 stage (defined as  one of the top four nodes has a fully developed leaf with a 3/16 inch pod) are off label.
  3. Finally, mind your wheel tracks. The research shows damage from ground applications may start to cut into yield. Says Dr. Conley, “Our research suggests that an adequate soybean stand (more than 100,000 plants per acre) planted in late April though mid-May can compensate for wheel tracks made when a field is sprayed at R1.” After then, it’s another story. Check here for the full details.