Time to think about fall weed control

Oct 07, 2022

With harvest activities starting to wrap up in some areas, farmers are looking at their fall weed control.

Weed Control Specialist Clark Brenzil says weeds need to be actively growing in order to get the best result.

Fall weed control or suppression is helpful to prevent the plants from flowering and setting seed prior to the crop coming up in the spring.

For perennial weeds you're looking at trying to control things like Canada thistle, dandelion, quackgrass and potentially foxtail barley in the fall.

Brenzil says for Canada thistle the ideal time for control is with a pre-harvest treatment of glyphosate.

"That's because you're looking at about a litre or about 360 grams of active ingredient per acre for that application. Whereas, if you go to a post-emergent application, you have to pretty much triple that rate in order to get the same amount in the plant, just because you've got proportionately less leaf area on that plant."

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Video: Dr. Emerson Nafziger: Nitrogen Fertilizer Rates for Corn

The Crop Science Podcast Show, Dr. Emerson Nafziger from the University of Illinois breaks down decades of nitrogen research. From the evolution of N rate guidelines to how soil health and hybrid genetics influence nitrogen use efficiency, this conversation unpacks the science behind smarter fertilization. Improving how we set nitrogen fertilizer rates for rainfed corn is a key focus. Discover why the MRTN model matters more than ever, and how shifting mindsets and better data can boost yields and environmental outcomes. Tune in now on all major platforms!

"The nitrogen that comes from soil mineralization is the first nitrogen the plant sees, and its role is underestimated."

Meet the guest:

Dr. Emerson Nafziger is Professor Emeritus of Crop Sciences at the University of Illinois at Urbana-Champaign, with degrees in agronomy from Ohio State, Purdue, and Illinois. His research has focused on nitrogen rate strategies and crop productivity. He co-developed the Maximum Return to Nitrogen (MRTN) model, which is widely used across the Midwest. His research spans N response trials, hybrid interactions, crop rotation effects, and yield stability.