Comparison of Stay-Green and Conventional Sunflower Desiccation in the Northern Great Plains
- Tim D. Larsona,
- Burton L. Johnson *b and
- Robert A. Hensonc
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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