This is Dr. Nathan Mueller, your local agronomist for Nebraska Extension. It has been a busy week for spraying burndown and soil applied herbicides. Winter annual weeds such as tansy mustard, field pennycress, and henbit had good growth with the warmer than normal March.
Let’s answer three questions for you in the next minute. First, can heavy winter annual weed pressure this spring cause yield loss in your corn or soybean crop? Yes, research in Nebraska and Kansas has shown that heavy stands of winter annual weeds can reduce corn and soybean yield.
Second, how much reduction in yield has been measured? A soybean yield loss of about 12% was measured in Nebraska when delaying herbicide application from March 15 to May 15. My research in Eastern Kansas shows that delaying weed control until corn planting reduces corn plant populations by 500 plants per acre, reduces early corn N uptake, and reduces corn yield by 8 bushels per acre compared to the earliest herbicide application in November or March.
Third, what can I do about it right now? Prioritize fields with heavy winter annual weed pressure to spray as soon as possible and don’t allow weeds to go to seed. Unfortunately, some henbit plants (the ones with the purple flowers) may have already produced seed. However, most winter annual weeds haven’t yet, so let’s get started on depleting that weed seed bank for next year.
To learn more about winter annual weed management, call me at 727-2775 or visit our local website at croptechcafe.org. Know your crop, know your tech, know your bottom line. This is Dr. Nathan Mueller, your local agronomist for Nebraska Extension on KTIC radio.
New Nebraska Extension Publication: Identification of Winter Annual Weeds