Weed Management Key for Conventional Soybeans

There has recently been renewed interest in weed control options for conventional soybean production. One of those options is the Calyxt High Oleic soybean.  These soybeans are a new identity preserved, non-GMO offering available through Agtegra.  We have partnered with Calyxt, Inc. to make this offering, sell seed and market the identity-preserved grain with a premium paid to the grower.  Please contact your local Sales Agronomist or Grain Originator with any questions on this program. Although there are many opportunities for growers with producing conventional soybeans, there are a few challenges as well. 
“Conventional soybeans may not have been planted in more than a decade on some operations, or some farmers may have never planted conventional soybeans,” says Brad Ruden, Agronomy Tech Services Manager for Agtegra.
Worst Offenders
Weed management is the first hurdle to overcome when growing conventional soybeans. One of the toughest to control is kochia.  Conventional soybeans should be placed on cleaner fields with less weed history.  Using an effective burndown prior to planting to take care of this early emerging weed, along with a very solid pre-emergence herbicide program are two more critical steps to controlling this weed. 
There are two other weeds in particular that are major offenders to watch out for—Palmer amaranth and common water hemp.
“Palmer amaranth is a newer invasive pigweed species with several local infestations known in the Agtegra service territory,” says Ruden.
Palmer amaranth is extremely aggressive and both it and common waterhemp have the capability of enormous seed production and rapid expansion. Both of these pigweeds are tall plants capable of effectively competing with crops.
“The key to controlling new infestations, especially if Palmer amaranth appears is to immediately identify and control the infestation when the patch is small, using traditional effective weed management programs plus spot weed control or even hand weeding to remove the plants before seed production, harvest or weed spread,” Ruden adds.
If you know what you are looking for, you can easily tell the difference between water hemp and other pigweed species. Look at the stem first, Ruden recommends.
“If it’s hairy, then the weed is probably redroot pigweed, which is a common pigweed. A smooth stem is most likely water hemp. A smooth stem with spiny bracts at the leaf petiole base is probably Palmer amaranth,” he says.
Key Management Steps
If you’re considering growing conventional soybeans in 2019, there are some key steps to take to help set your program up for success during this growing season and beyond:

  • Site selection—You must choose fields that have a lower history of weed pressure. Conventional herbicides are less successful with increased pressure.
  • Start clean—You must start the year clean. Weeds cannot be allowed to get ahead of residual herbicides.
  • Use overlapping residuals—Use effective residuals to extend control.
  • Keep weeds small—Post-emergence herbicides are only effective on small weeds. Weeds must be controlled when they are less than four inches tall.
  • Full rates with multiple modes of action—Use full rates of effective herbicides throughout the year. Use multiple modes of action on every acre. Kochia takes at least three modes of action.

It is extremely difficult to rely on a total post-emergence conventional soybean weed control program.
Be sure to contact your local agronomist for expert advice on weed control programs in your area.


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