Yield Environment Affects Glyphosate‐Resistant Hybrid Response to Glyphosate

Abstract

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.

Pleiotropic effects of herbicide-resistance genes on crop yield: a review

“…99 In addition, the use of the appropriate herbicide on the corresponding herbicide-resistant cultivars led to improved yields in weed-infested conditions, mostly because it eliminated toxic effects of other herbicides on conventional cultivars. 90 There were a few exceptions, as for glyphosate, which causes delayed maturity of cotton through an effect on pollen production, 100,101 but that has no impact on yield. 80,98 From a practical perspective, the net effect of resistance alleles or transgenes is determined by a balance between the benefits of the resistance gene effect and its associated cost.…”

“…In particular, a wider choice of resistant cultivars makes it possible to select for better yields and adaptation to local conditions . In addition, the use of the appropriate herbicide on the corresponding herbicide‐resistant cultivars led to improved yields in weed‐infested conditions, mostly because it eliminated toxic effects of other herbicides on conventional cultivars . There were a few exceptions, as for glyphosate, which causes delayed maturity of cotton through an effect on pollen production, but that has no impact on yield .…”

“…Very few comparisons of isogenic material have been published, or perhaps even investigated. Several studies showed both differences and no differences among different cultivars, and these variable results were attributed to genotype/environment interactions.…”

Comparisons of Herbicide Treated and Cultivated Herbicide-Resistant Corn

“…Ferrell and Witt [7] determined economic net returns for corn using glyphosate technology were similar to those of corn produced with conventional herbicide systems. However, Thelen and Penner [8] reported slight yield reductions in corn grain yields with the application of glyphosate under certain temporal high-yield environments. Krausz et al [9] reported that height and grain yield of a glufosinateammonium-resistant corn hybrid was not different from a nonresistant isoline grown using a conventional herbicide for weed control.…”

Stacked Corn Hybrids Show Inconsistent Yield and Economic Responses in New York

“…Thelan and Penner (2007) evaluated about 25 glyphosate‐resistant corn hybrids with near‐isolines in Michigan at three sites from 2002 to 2006 and reported that, in low‐yield environments, the glyphosate‐resistant hybrids yielded about 5% higher than their near‐isolines, but in high‐yield environments the near‐isolines yielded about 2% higher than their glyphosate‐resistant counterparts. Weed control did not influence yield in the study, so Thelan and Penner (2007) concluded that that in certain high‐yield environments, slight injurious effects of glyphosate metabolites on corn may occur.…”