Yield Environment Affects Glyphosate-Resistant Hybrid Response to Glyphosate
- Kurt D. Thelen * and
- Don Penner
The yield response of glyphosate-resistant corn (Zea mays L.) to glyphosate across a broad range of temporal yield environments is not well understood. Field experiments were conducted at three Michigan locations over a five year period (2002–2006) comparing corn grain yield of glyphosate-resistant hybrids as affected by a glyphosate-based or conventional herbicide system. Regression analyses of yield data showed a dual glyphosate-resistant hybrid yield response to glyphosate based on the temporal yield environment for a given year. Under average- to low-yield environments, the glyphosate-based herbicide system resulted in greater grain yield. However, under temporal high yield environments, the conventional herbicide system resulted in greater grain yield. Threshold corn grain yields above which the conventional herbicide system resulted in higher grain yield and below which the glyphosate-based herbicide system resulted in higher grain yield were determined to be: 11.38 (± 0.13), 12.73 (± 0.14), 13.97 (± 0.25), and 11.62 (± 0.10) Mg ha−1 respectively for the Huron, Montcalm, Saginaw, and combined site average. Differences in weed control levels were not observed and weed control did not appear to be a factor in grain yield determination. The results suggest a slight corn grain yield reduction from glyphosate under certain temporal high-yield environments.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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