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Crop roundup: Yield-Limiting Factors for Continuous Corn

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. 

“The program is extremely beneficial to the research and academic community as its goal is not to examine product-specific issues, but rather look at the broader challenges farmers face when dealing with corn rootworm,” said Dr. Spencer, entomologist with the Illinois Natural History Survey, who received one of this year’s grants. “I’m honored to receive this grant, which will help further my research into the behavioral, physiological, and ecological factors that contribute to the western corn rootworm’s adaptations to a variety of pest-management strategies.”

The CRW Knowledge Research Program is guided by a 10-person Advisory Committee that is cochaired by Dr. Steve Pueppke, associate vice president for research and graduate studies and AgBioResearch director at Michigan State University; and Dr. Dusty Post, Monsanto’s global insect management lead. Additional committee members include experts from academia and agricultural organizations who were selected based on their expertise in corn rootworm biology and insect-management practices.

“The valuable research that is being generated through this program is continuing to improve our understanding of this challenging pest and provide economical, practical, and sustainable solutions for farmers,” said Post.

The six awards granted focus on a number of items from evaluating how best to manage corn rootworm under current production practices to evaluating strategies to delay the onset of resistance evolution. The award recipients are:

  • Joseph Spencer, University of Illinois
  • Nicholas Miller, University of Nebraska-Lincoln
  • Paul Mitchell, University of Wisconsin
  • Blair Siegfried, University of Nebraska-Lincoln
  • Douglas Golick, University of Nebraska-Lincoln
  • Mike Caprio, Mississippi State University
  • Christian Krupke, Purdue University

A listing of the winners and background on their projects is available on the Monsanto Corn Rootworm Knowledge Program Web page.

“The Corn Rootworm Knowledge grant has enabled field and laboratory research on western corn rootworm that would not have been possible without this support,” said Aaron Gassmann of Iowa State University and Kenneth Ostlie of the University of Minnesota, two recipients of last year’s grants. “Bt corn for management of western corn rootworm is a valuable tool for farmers in the Corn Belt. Information gained through this research will help to preserve the efficacy of Bt corn for management of western corn rootworm, and will enhance the ability of farmers to effectively manage this pest.”

Sources: DuPont Pioneer, BASF, Monsanto

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