Long-Term Study Shows Yield Key in Weed Control

Research at Northern Illinois Agronomy Research Center compares residual and non-residual herbicide systems in Roundup Ready corn and soybeans.

Apr. 18, 2026 at 8:35am

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A bold, abstract painting in muted earth tones featuring sweeping geometric arcs, concentric circular patterns, and precise botanical spirals, conceptually representing the structural order and natural forces at play in no-till weed management and crop production.An abstract scientific visualization captures the complex interplay of weed control strategies and crop yields in no-till farming.Shabbona Today

A 5-year study at the Northern Illinois Agronomy Research Center in Shabbona, Illinois compared five different weed control systems in Roundup Ready corn and soybeans. The results showed that while there was little difference in weed control between the programs, the yields varied significantly, with post-only programs not maintaining the same yields as pre-emergence followed by post-emergence applications.

Why it matters

This long-term research provides valuable insights for no-till farmers on the importance of timing weed removal to maximize yields, rather than just focusing on the level of weed control. The findings can help inform best practices for herbicide application strategies in Roundup Ready crops.

The details

The five weed control systems evaluated in the study were: 1) pre-emergence only, 2) pre-emergence followed by a post-emergence with a residual, 3) pre-emergence followed by a post-emergence without a residual, 4) post-emergence only with a residual, and 5) post-emergence only without a residual. The objective was to determine how long herbicide-resistant corn and soybeans can tolerate weeds and the best time to remove weeds to maximize no-till yields.

  • The 5-year study was conducted at the Northern Illinois Agronomy Research Center in Shabbona, Illinois.
  • Researchers looked at weed control and yields over the course of the 5-year period.

The players

Dawn Nordby

A University of Illinois graduate student who worked on the study.

Northern Illinois Agronomy Research Center

The research facility in Shabbona, Illinois where the 5-year study was conducted.

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What they’re saying

“For corn, there was very little difference in weed control comparing these programs, but looking at the yields is where we saw a significant difference.”

— Dawn Nordby, University of Illinois graduate student

“The post-only programs don't maintain the yields that we get from a pre and post or an early post, late post combination.”

— Dawn Nordby, University of Illinois graduate student

What’s next

The researchers plan to publish the full results of the 5-year study in an academic journal later this year.

The takeaway

This long-term research highlights that for no-till farmers, the timing and strategy of weed removal is more important for maximizing yields than just achieving a high level of weed control. The findings can help guide best practices for herbicide application in Roundup Ready crops.