Defeating Weeds in Corn
This corn field is infested with velvetleaf. If weeds, like velvetleaf, are not controlled when they are small they can lead to serious yield loss.
Chris Boerboom, University of Wisconsin extension weed scientist, recently explored two interesting observations on weed management that can reduce profit in glyphosate-tolerant corn in Wisconsin Crop Manager., Research shows that corn yield is lost when weeds are sprayed at greater than 4 inches. In 30 surveyed corn fields sprayed post-emergence in Wisconsin in 2008, more than 75 percent of the fields had an average weed height of 6 inches when sprayed. Yield loss predictions suggest an average loss of 6.5 percent. With 150 bu/A and $4 corn, this is a $39 per acre loss!
Nitrogen studies were also conducted. In the two years of the study, 12-inch weeds pulled 25 pounds and 67 pounds of nitrogen, respectively, per acre from the soil, and corn yield was cut an average of 12 bu/A and 18 bu/A compared to when weeds were controlled at 4 inches. Interestingly, they found when high rates of nitrogen were applied, yield could be regained. But with high nitrogen costs, this approach isn't cost effective.
These observations highlight the need for timely weed management to protect corn yields. The use of a pre-emergence residual herbicide, like Lumax®, can greatly increase the window for post-emergence herbicide applications and can lay the foundation for season-long protection. Managing weeds when they are small, around 4 inches (about the size of a pop can), is imperative. As input costs increase, every bushel lost is more impactful on the bottom line.
How tall are weeds when you make your post-emergence application? Do you approach weed management differently in glyphosate-tolerant corn compared to conventional varieties? How severe have yield losses been due to weed competition in corn?
Important: Always read and follow label instructions before buying or using these products. Lumax are Restricted Use Pesticides. Lumax® is a registered trademark of a Syngenta Group Company.