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Can Off-Target Dicamba Boost Soybean Yields?
There’s lots of chatter on social media and coffee shops these days about off-target dicamba actually raising soybean yields.
The line often goes like this: “We got hit and had the best yield of soybeans we've had in a long time. I've heard that from more than one person, too.”
So is it real?
Well, it’s almost akin to that old Brylcreem ad that touted “A little dab’ll do ya” on men’s hair. In the herbicide world, it’s called herbicide hormesis. At low doses like those that occur in off-target movement, synthetic auxin herbicides like dicamba actually can boost yields.
There’s a catch, though. No one actually knows when it will happen.
“It can occur, but no one has been able to figure out a rate at which it will work,” says Kevin Bradley, University of Missouri (MU) Extension weed specialist.
On the downside, there is plenty of evidence that off-target dicamba will cut yields.
“There are 15 to 20 refereed journal articles published since the 1960s that if you spray dicamba on soybeans (off target) you will get yield loss," says Bradley. "It varies based on when the injury occurs. When you injure soybeans early in the season, you more than likely will not see an effect. But if you injure them at R1 (early bloom) or later, you will have a yield loss.”
MU research shows 1/200 of a labeled rate for dicamba caused 14% yield loss after an R2 (full flower) application.
Even if yield loss doesn’t occur, it doesn’t excuse off-target dicamba, says Bradley.
“There have been all kinds of arguments that it will not cause yield loss,” says Bradley. “I don’t know where we have gone as an industry (saying) that it is OK to drift on someone else without causing yield loss. But apparently, that is the latest argument.”