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SUNFLOWER

Comparison of Stay-Green and Conventional Sunflower Desiccation in the Northern Great Plains

^a Pioneer Hi-Bred Int., Inc., Brookings, SD 56007
^b Dep. of Plant Sci., North Dakota State Univ., Fargo, ND 58105
^c Carrington Res. Ext. Center, Carrington, ND 58421

^* Corresponding author (burton.johnson{at}ndsu.edu).

Desiccant effectiveness in hastening sunflower (Helianthus annuus L.) harvest is based on research conducted for conventional sunflower hybrids; however, information is lacking regarding plant drydown response of more recently developed stay-green hybrids to desiccation. Stay-green and conventional sunflower hybrids were evaluated for plant drydown response to desiccant and control treatments in 2000 and 2001 at Carrington, Casselton, and Prosper, ND. The experiment was a randomized complete block arranged in a split-split-plot design with desiccation, hybrid, and harvest date representing main, sub-, and sub-subplot, respectively. Pioneer Hy-Bred International oilseed hybrids ‘6338’ (stay-green) and ‘63M91’ (conventional), and nonoilseed Seeds 2000 stay-green hybrid ‘Bigfoot’ were evaluated for plant drydown response under natural (control) conditions and when desiccated with paraquat (1,1'-dimethyl-4,4'bipyridinium dichloride) applied at the labeled rate. Timing of desiccant application was based on visual characteristics of the capitulm and targeted at physiological maturity when achene moisture 350 g kg^–1. Four harvest dates occurred at 7-d intervals following desiccant application where achene, receptacle, and stalk moistures were evaluated. Results indicated hybrid achene-moisture response across harvest dates was similar for the desiccated and control treatments, although desiccation hastened achene-moisture loss to harvestable levels by 7 d. Harvestable achene and receptacle moistures were concurrent for the conventional hybrid 63M91, however, high receptacle moisture for the stay-green hybrids 6338 and Bigfoot could prevent harvest even though achene moisture was at harvestable levels. Desiccation hastened hybrids 63M91, 6338, and Bigfoot receptacle drydown to harvestable levels by 7 d, however 63M91 reached harvestable moisture 5 d earlier than the stay-green hybrids. Receptacle and stalk moisture differences indicated greater receptacle than stalk moisture differences between stay-green and conventional hybrids. Desiccation is an important harvest management practice to hasten harvest especially for stay-green hybrids where receptacle moisture determines harvestability. Increased levels of the stay-green trait in sunflower may result in desiccation becoming a more common harvest management practice.

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Received for publication July 24, 2007.