Relationship Between Yields and Weeds

As the spring planting season starts to take shape here in the South, many growers might not think weeds are a factor that can impact corn yield. Dean Grossnickle, an agronomy service representative with Syngenta, says higher yield potential really starts with early-season weed control. Grossnickle says weeds that emerge with the corn plant impact its overall health.

“These weeds do impact corn in a lot of different ways, but weeds present at corn emergence are an immediate source of stress and cause corn to enact a series of defensive measures. Corn stalks will grow taller and also those weeds will grow wider to better compete for sunlight which will also reject the sun's rays. Additionally, corn leaves grow parallel to the row versus out to the row to avoid competing directly for sunlight. Unfortunately, really this alignment is not optimal for absorbing sunlight and these changes can negatively impact yield over time, and you may not be able to overcome that with post-emergence weed control.”

Further, Dr. Bill Johnson, professor of weed science at Purdue University, says the loss of nitrogen to weeds can impact yield.

“It's really important early in the year to have clean fields when the corn comes up because there's two things that happen. Number one, it's competing for nutrients and water. So, most of the time in the eastern Corn Belt, we have wet springs. The moisture is not an issue. You do have that competition for nitrogen. If supplemental nitrogen is applied, many times you can overcome that early-season competition for nitrogen.”