By Daniel Davidson
DTN Contributing Agronomist
There's a whole lot of green along the I-70 corridor and points south this fall and, by the way, that's not winter wheat or intentionally seeded cover crops emerging. Volunteer corn and soybeans shows us just how much seed gets dropped each year.
How much are we actually losing? Two seeds per square foot equal a bushel of grain per acre. That vastness of the green carpet makes even more sense when you think that a 1-bushel-per-acre loss translates to approximately 90,000 kernels or plants per acre; substantially more than a typical planting rate.
The good news is most of that volunteer corn will not survive the winter, and a good hard freeze should reduce the amount of volunteer corn you'll see in 2017. Soybeans should kill out too.
Corn seed has a bit of dormancy (a couple weeks at most), but in warm and moist soils and with corn being harvested early, there is plenty of time for germination. We may drop just as much in the I-80 corridor, but we don't see as much fall volunteer emergence. Where corn tends to be harvested later, the soil is cooler and kernels that don't germinate until next year may require a herbicide to terminate before planting.
Weak stalks, weak shanks, lodging and eardrop contribute to this second round of seedlings. However, it is individual kernels coming out the back of the combine that are often the culprits. Corn ears have tips and butts, and when being threshed, some of these kernels flow out the back of the combine. Also, kernels that are lighter than the bulk of the kernels will flow out the back of the combine.
A good operator will monitor combine loss and adjust his combine and harvesting speeds accordingly to keep losses to 1 to 2 bpa. Unfortunately, with such large corn yields, tough stalks, lots of trash and the desire to go fast means growers tend to open up the sieves a bit to get all that material through the combine. Those actions result in more potential volunteer corn plants.
Fortunately, in next year's soybean crop you can control volunteer corn with a grass herbicide such as Select Max. That's harder in continuous corn where those volunteers can compete with the new crop.
Soybeans will also germinate in the fall. They have no real dormancy period and will show up right away. This fall, the weather and soils have been warmer than normal, and I am seeing a fair amount of volunteer soybeans even north of I-80. But, like corn, a hard freeze will terminate them. Unlike corn, soybean seed won't survive over winter so won't volunteer next season, so no herbicide control is necessary.
These days, growers are planting an array of cover crops to protect the soil from erosion, suppress winter annual weeds, scavenge nutrients left unused by the previous crop and stimulate soil health (think roots in the ground all year around). Volunteer corn and soybeans that germinate and grow in the fall can provide some of the same benefits of cover crops either alone or in combination with other species. Like many cover crop species, they will terminate with a hard freeze over winter.
Livestock farmers can make the best of the volunteer situation. Grazing stalks tends to significantly reduce the likelihood of volunteer corn. There's also some research at the University of Nebraska that shows grazing stalks can reduce the incidence of sudden death syndrome (SDS) in the following soybean crop. For more information on stalk grazing go here: http://cropwatch.unl.edu/…
Cattle grazing volumes of volunteer soybeans could potentially lead to bloat concerns with young green plants. For more information: https://jenreesources.com/…
Dan Davidson can be reached at AskDrDan@dtn.com
Follow Dan Davidson on Twitter @dandavidsondtn
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