Weed control in non-GMO soybeans
BROOKINGS, S.D. – In some markets, non-genetically modified organism soybeans are bringing $1 or more per bushel than genetically modified (GMO) soybeans.
Weed control is a hesitation South Dakota farmers have when making a decision to plant non-GMO seeds in 2017 to take advantage of this potential premium.
“Many farmers wonder if it is possible to continue no-till farming practices and plant non-GMO crops with resistant weeds growing in their fields. The answer is ‘yes,’” said Gared Shaffer, SDSU Extension Weeds Field Specialist. “With a little more homework producers can control weeds and keep their soil healthy.”
Necessary components of weed management in non-GMO soybeans
Weed control basics remain the same in non-GMO versus GMO fields, Shaffer explained.
Begin with a weed-free field at planting
“This means, do not plant unless the weeds prior to planting are controlled,” Shaffer said. “I cannot stress this enough with any crop, but you need to start with a clean field before planting.”
To accomplish this, Shaffer encourages the use of a burndown herbicide before or at planting. He recommends a burndown herbicide which provides a broad spectrum of weed control such as glyphosate, paraquat, glufosinate(Liberty®). Other herbicides that may aid in weed control could include 2,4-D ester and a metribuzin product.
2. Pre and post herbicide applications
Applying pre-herbicides prior to planting gives farmers some time for a post application, as well as providing soybeans with a head start. “If needed a combination of burn-down with pre-herbicide could be used for extra control” Shaffer said.
“If needed, farmers can also apply a post-herbicide when weeds are less than 4 to 6-inches tall after soybean emergence,” Shaffer said.
The timeline for this may be anytime between two to six weeks after soybean emergence.
“The biggest decision here, is to choose herbicides that will provide a window to control early weeds and give the beans a head start,” Shaffer said.
Examples of pre-herbicides for control depending on weed pressure, could include: Authority Assist®, Authority First®/Sonic®, Canopy®, Valor XLT®, Gangster®, Metribuzin, Python®, Scepter® and Valor®.
As for post-herbicide control, Shaffer said it is best to control weeds at 2 to 4-inches tall.
“If possible don’t allow them to reach over 6 inches tall when relying on herbicide control,” he said.
Also, use a spray volume of at least 15 gallons per acre (gpa) and nozzles that produce medium-sized droplets.
Some post-herbicide options include: Flexstar® or Rhythm® + Select®, Fusion®, etc (grass herbicides) + COC or MSO + AMS. Other options could include FirstRate®, Classic® or Synchrony®. If applied at 28 percent, this may improve weed control but also increase crop injury. If necessary and for late emerging weeds, apply Phoenix® or Cobra® three weeks later if troublesome broadleaf weeds exist, add a grass herbicide if late emerging grasses are a problem.
What about fall applications?
Shaffer discourages fall herbicide application. “Applications of herbicides in the fall are not as long lasting or effective compared to those applied in the spring, especially if the goal is to use fall application as a substitute for a spring treatment. There are options for fall application but usually they end up costing more and then a spring application is almost always necessary.”
One combination that may be an option in the fall, Shaffer said may be glyphosate + 2,4-D or 2,4-D plus a low rate of a chlorimuron containing product.
Shaffer encourages growers to also consider non-herbicide options which increase cash crop growth and decrease weeds. These methods include: crop rotation, cover crops, row spacing and livestock integration.
For more information, contact Gared Shaffer at firstname.lastname@example.org or 605-626-2870.
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Drought stressed forages can be high in nitrates and may be potentially toxic to cattle. Photo credit Troy Walz.