Rain Rain Go Away Do I Switch to Soybean From Zea May(s)

Shawn P. Conley, Soybean and Wheat Extension Specialist

As growers begin to contemplate switching intended corn acres to soybean, here is a quick checklist of points and questions to consider or reconsider before making that switch.

  • Do I have a residual corn herbicide down that is not labeled for soybean? If the answer to this question is yes, then Don’t Switch Crops. It doesn’t matter how much rain we have had. Plant back label restrictions must be followed.
  • What is my cost of production and weather outlook for finally getting this crop in the ground? Dr. Joe Lauer just posted his corn replanting and yield loss guide. Expected corn grain yield if planted in the next 8 days would range from ~70 to 85% of maximum yield. Soybean yield would roughly be 85 to 90% of maximum yield based on your maturity group and final planting date. Run your numbers, talk to your lender, and see what gives you the greatest ROI.
  • I already put out all my nitrogen (or for WI growers – I am following alfalfa). What potential impacts will that have on my soybean crop?
    • Dr. Emerson Nafziger did a great job shedding light on question #1 regarding N management… How Much Nitrogen is Gone?
    • Knowing that most of the N will likely be available to the soybean crop, there is a risk of lush vegetative growth, possible lodging (harvest efficiencies) and higher risk for white mold. However soybean total dry matter and growth will be behind due to its late planting so this risk is lessened. I would most be concerned about white mold. Luckily, we have Dr. Damon Smith at UW Madison and he will keep us updated as to potential white mold risk this summer so stay tuned for possible next steps!
    • Soybean is very efficient at N uptake and partitioning so that N will likely still see its way to the elevator.
    • If you decide to plant soybeans into these high N fields, I would pull the inoculant from the seed treatment mix if this field has seen regular soybean cropping (2 years out of the last 5). Biological nitrogen fixation will be delayed due to free N availability and the soybean crop will rely on background soil rhizobia for subsequent infection.
  • Will I be planting elite soybean genetics if I switch or will I be planting a dog? Even in late planted situations, we are still roughly at 90% maximum yield potential. Don’t ditch your elite corn genetics to plant junk beans. Please see our Wisconsin Soybean Performance Trials for more information on variety selection.
  • Lastly, how much of my 2017 crop is marketed and how flexible are my options. Even though plantings of both crops are delayed, if we continue to see poor corn crop ratings across the ‘I’- states and then see another million acres of corn go to soybeans, I  believe this will put significant pricing pressure on both crops.
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