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Crop roundup: Yield-Limiting Factors for Continuous Corn

Kacey Birchmier Updated: 03/31/2014 @ 11:45am Agronomy & Conservation Editor for Successful Farming and Agriculture.com. I grew up on a fourth-generation farm in central Iowa. Follow me on twitter - @KaceyBirchmier.

One study looks at yield-limiting factors for continuous corn, another at the effectiveness of preemergence herbicides with multiple sites of action. Grants announced from Monsanto corn rootworm knowledge research program.

DuPont Pioneer study reveals yield-limiting factors for continuous corn
Maximizing yield with continuous-corn fields is more difficult than with corn-soybean rotations. This is true even with intensively managed continuous corn systems, as yield-limiting factors are not fully understood. A recent six-year study conducted by DuPont Pioneer agronomists in Illinois reported that continuous corn yielded 25 fewer bushels per acre than corn-soybean rotations, and identified three factors — soil nitrogen (N) supply, continuous corn history, and weather — as responsible for more than 99% of the continuous corn yield penalty.

  • To explain the difference between corn-soybean rotations and continuous corn yields, N supply was, by far, the most important factor. The continuous corn yield penalty decreased as intrinsic soil N supply capacity increased.
  • The number of continuous corn years was the second-most important component of the yield penalty. The difference between corn-soybean rotations and continuous corn yields increased with years in continuous corn.
  • The third driver was weather. The continuous corn yield penalty increased as weather conditions limited N availability to continuous corn; this occurred to a much greater degree than in corn-soybean rotations.
  • The study’s results indicate that positioning continuous corn on highly productive soils and effectively managing corn residues are two of the most important practices for consistently achieving high continuous corn yields.

Growers farming continuous corn acres can employ several best-management practices to maximize yields, including hybrid selection, tillage, soil fertility, and weed and insect control.

Studies demonstrate importance of preemergence herbicides with multiple sites of action
With more than 60 million U.S. acres affected by glyphosate-resistant weeds and nearly every state affected by some form of resistant weeds, the challenge facing growers is increasing every year. In a 2013 survey of Midwest growers, BASF found that 76% will be changing their weed-management strategies in 2014 to address this issue.

Multiple sites of action
BASF scientists tested the effectiveness of Verdict herbicide for control of weeds in preemerge and preplant applications. Verdict herbicide, powered by Kixor herbicide technology, combines the active ingredients in Outlook herbicide and Sharpen herbicide to provide two sites of action.

“There are two key reasons for choosing products that use multiple effective sites of action,” said Mark Oostlander, BASF technical market manager, herbicides. “The first is better weed control in general, and the second is superior control of resistant weeds.”

If there is a weed resistant to one of the sites of action, having two or more provides backup.

To show a living demonstration of these advantages, scientists conducted a greenhouse trial where they took soil and weed seeds – foxtail, common waterhemp, and common ragweed – from fields throughout the U.S. and grew weeds in four separate pots. They then applied a different herbicide to each of the pots; one with Outlook herbicide, one with Sharpen herbicide, and one with Verdict herbicide. The fourth pot was left untreated. The multiple sites of action in Verdict herbicide proved to have the most complete control on all three of the weeds planted.

Residual control
To show the importance of using a preemerge herbicide, BASF scientists conducted the same greenhouse trial two weeks apart. Four weeks after the first trial started, the soil still remained weed-free.

Monsanto corn rootworm knowledge research program announces grants.
Monsanto Company has announced that six new recipients will be awarded research grants as part of the Corn Rootworm Knowledge Research Program.  The program, which started in early 2013 and recently was extended to 2016, provides merit-based awards of up to $250,000 per award per year for up to three years for outstanding research projects that address specific aspects of corn rootworm biology, genomics, and management issues. 

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