Evalutation of Weed Management in Glyphosate-Resistant Corn (Zea Mays) as Affected by Preemergence Herbicide, Timing of Postemergence Herbicide Application, and Glyphosate Products

Roundup WEATHERMAX?;Roundup UltraMAX®;diammonium salt of glyphosate;potassium salt of glyphosate;Roundup Original?;Glyfos® X-TRA;Glyphomax?;Gly Star? Original;isopropylamine salt of glyphosate;weed control;Touchdown Total?;Touchdown®;ClearOut 41 Plus?;crop tolerance;Glyfos®

Parker, Robert Gary ; Dr. Alan C. York, Committee Chair,Parker, Robert Gary ; Dr. Alan C. York ; Committee Chair

University:North Carolina State University

关键词: Roundup WEATHERMAX?;    Roundup UltraMAX®;    diammonium salt of glyphosate;    potassium salt of glyphosate;    Roundup Original?;    Glyfos® X-TRA;    Glyphomax?;    Gly Star? Original;    isopropylamine salt of glyphosate;    weed control;    Touchdown Total?;    Touchdown®;    ClearOut 41 Plus?;    crop tolerance;    Glyfos®;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/887/etd.pdf?sequence=1&isAllowed=y

美国|英语

来源: null

【 摘 要 】

Cotton and soybean resistant to glyphosate are widely planted in the United States.Ninety-five percent of the cotton and 85% of the soybean in North Carolina is glyphosate-resistant (GR).Rapid adoption of the technology is attributed to broad spectrum weed control, convenience of glyphosate-based weed management systems, and greater rotational crop flexibility.Corn resistant to glyphosate is less widely grown, but plantings are expected to increase.Wide-spread planting of GR crops in the United States and glyphosate patent expiration has led to a proliferation of glyphosate products.Growers have questioned their advisors on efficacy and crop tolerance of many of these products.Field experiments were conducted to evaluate 10 glyphosate products, representing isopropylamine, diammonium, and potassium salts, applied postemergence (POST) and postemergence-directed (PDIR) at 630 and 1680 g ae/ha for GR corn and GR cotton tolerance and weed control.There were no differences among products for control of six annual grass and 10 annual broadleaf weed species.No injury to corn from any glyphosate product at 630 or 1680 g/ha or to cotton from 630 g/ha was noted at any of seven locations.ClearOut 41 Plus™, an isopropylamine salt of glyphosate, and Roundup WEATHERMAX™, a potassium salt of glyphosate, applied POST at 1680 g/ha injured cotton 27 to 30% and 10 to 17%, respectively, at 3 of 7 locations. No cotton injury was noted with Glyfos®, Glyfos® X-TRA, Glyphomax™, Gly Star™ Original, Roundup Original™, Roundup UltraMAX®, Touchdown®, or Touchdown Total™.No differences were noted among glyphosate products or between rates for corn or cotton yield or cotton fiber properties.Field studies were conducted at six sites during 2002 and 2003 to evaluate weed control and glyphosate-resistant corn response to glyphosate and nicosulfuron plus atrazine applied POST as affected by PRE herbicide and timing of POST herbicide application.Treatments included a factorial arrangement of no herbicide or alachlor plus atrazine PRE at one-half the manufacturer's suggested use rates, glyphosate or nicosulfuron plus atrazine POST, and POST herbicides applied timely or when application delayed by 1 or 2 wks.All treatments included glyphosate postemergence-directed.Common lambsquarters, common ragweed, Palmer amaranth, prickly sida, and smooth pigweed were controlled at least 94%, with no differences among treatments.Broadleaf signalgrass, fall panicum, goosegrass, and large crabgrass were controlled at least 96% by all glyphosate treatments while control by nicosulfuron plus atrazine without PRE herbicide decreased as application timing was delayed.Sicklepod was controlled at least 94% when POST herbicides were applied timely, but control by both POST herbicides decreased with delayed application regardless of PRE herbicide.Entireleaf morningglory, ivyleaf morningglory, pitted morningglory, and tall morningglory were controlled 93% or greater when either POST herbicide was applied timely.Control by both POST herbicides decreased as application was delayed, with glyphosate being affected more by timing than nicosulfuron plus atrazine.Corn grain yield was similar with glyphosate and nicosulfuron plus atrazine following the PRE herbicide regardless of application timing while yield decreased as POST herbicide application was delayed in the absence of PRE herbicide. A field study was conducted to evaluate weed control and grain yield of 13 GR corn hybrids in 2002 or 17 GR hybrids in 2003 treated with a conventional or glyphosate-only herbicide system.Two non-transgenic hybrids were included for comparison.The conventional herbicide system consisted of s-metolachlor plus atrazine at 870 plus 1130 g ai/ha, respectively, applied PRE followed by ametryn at 1120 g ai/ha postemergence-directed (PDIR).The glyphosate-only system consisted of glyphosate at 840 g/ha applied POST and PDIR.Entireleaf morningglory, ivyleaf morningglory, pitted morningglory, and tall morningglory were controlled 98% or greater in the glyphosate-only system and 90 to 94% in the conventional herbicide system.Annual grasses, consisting of broadleaf signalgrass, goosegrass, and large crabgrass, common lambsquarters, common ragweed, smooth pigweed, and Palmer amaranth were controlled 96% or greater by both herbicide systems.The interaction of herbicide system by hybrid was not significant for corn grain yield.However, in 2003 there was a herbicide system affect on yield at the 10% level with the conventional system yielding higher than the glyphosate system. Experiments were conducted with corn at four sites in 2002 and 2003 to compare glyphosate-based herbicide systems to conventional herbicide systems in conventional and no-till tillage systems.Herbicide treatments included: s-metolachlor plus atrazine PRE or no PRE; POST herbicide treatments were nicosulfuron plus rimsulfuron plus dicamba, glyphosate alone or with atrazine, and no POST herbicide; and PDIR treatments included glyphosate, ametryn, or no PDIR herbicide application.In 2002, entireleaf morningglory, ivyleaf morningglory, pitted morningglory, and tallmorningglory where controlled 93% or greater 2 wk after POST herbicide application (WAP) by all treatments except for those not receiving a POST herbicide application. By 2 wk after PDIR herbicide treatment (WAPD), control was higher in plots receiving a PDIR herbicide treatment compared to all other treatments.Annual grasses and sicklepod were controlled 96% or greater 2 WAP with all treatments receiving a POST herbicide application.However, in the absence of a PDIR herbicide application, control was reduced up to 40 percentage points 2 WAPD.Palmer amaranth and common ragweed were controlled at least 99% in the no-till tillage system by both herbicide programs, however, in the conventional tillage system control was lower with the conventional herbicide program compared to the glyphosate system.Smooth pigweed was controlled completely by both herbicide systems regardless of the tillage system used.There were no differences in grain yield in 2002 between tillage or herbicide systems.However, in 2003, yields at one location varied by 1010 kg/ha, with the conventional tillage system yielding higher than in the no-till.Net returns varied according to grain yield, which varied among herbicide programs and tillage systems.