Tuesday, 8 November 2005
11

Sunflower Desiccation with Glyphosate.

Robbie A. Holthusen, Burton L. Johnson, Kirk A. Howatt, Paula J. Petersen, and Robert A. Henson. North Dakota State Univ., 1301 12th Ave N, Department of Plant Science, Lofsgard Hall 480D, Fargo, ND 58105

Few options are available for commercial desiccation of sunflower (Helianthus annuus L.). The study objective was to evaluate glyphosate as a potential desiccant in sunflower. The study was conducted at two locations, Casselton and Carrington, North Dakota in 2005. The experimental design was a RCBD in a split plot arrangement with glyphosate application timing being the main plot and harvest date the subplot. Glyphosate application occurred at 720 g/kg (Gly-1) and 620 g/kg (Gly-2) achene moisture, and harvest dates occurred at 7d intervals following glyphosate applications until achene moisture reached 150 g/kg. Receptacle moisture levels were also determined at each harvest date. Yield was reduced 23% for the Gly-1 treatment compared to the control, but yield was similar between the control and Gly-2. The control was higher for 1000 achene weight and oil content compared to Gly-1, and higher than Gly-2 for 1000 achene weight. Oil content and 1000 achene weight were higher for Gly-2 compared to Gly-1. At harvest date six, Gly-1 was nearing harvestable achene moisture of 150 g/kg, but the control was above 300 g/kg achene moisture. The Gly-1 treatment reached harvestable receptacle moisture content of below 400 g/kg at the seventh harvest date where as the control was at 600 g/kg receptacle moisture. At harvest date five, Gly-2 was nearing harvestable achene moisture where as the control was above 300 g/kg. At the sixth harvest date receptacle moisture for Gly-2 is nearing harvestable moisture and the control is above 600 g/kg. Glyphosate application did not reduce yield or oil content when applied at lower achene moisture levels, but timing of application is important since application at high achene moisture levels was shown to reduce yield and oil content.

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