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Title: Corn gluten meal as an alternative organic preemergence herbicide for onions (Allium cepa L.)

item Webber Iii, Charles

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/4/2007
Publication Date: 2/4/2008
Citation: Webber III, C.L., Shrefler, J.W. 2008. Corn gluten meal as an alternative organic preemergence herbicide for onions (Allium cepa L.) [abstract]. Weed Science Society of America, February 4-8, 2008, Chicago, Illinois. Paper No. 34.

Interpretive Summary:

Technical Abstract: Onions (Allium cepa L.) are a potential alternative crop for Oklahoma and northeast Texas and corn gluten meal (CGM) is an alternative organic preemergence herbicide. Successful onion production is dependent on reliable weed control because of the onion’s slow growth rate, short height, non-branching plant structure, low leaf area, and shallow root system. Corn gluten meal is a certified organic material with potential as a preemergence or preplant incorporated herbicide for organic crop production. In addition to weed control efficacy, it is important to also determine the crop safety of any proposed herbicide. In 2002 and 2003 field research was conducted in southeast Oklahoma (Lane, OK) to determine the impact of organic and synthetic preemergence herbicides on weed control efficacy, crop safety, and onion yields (cv. Hybrid Yellow Granex PRR). The 9 organic treatments evaluated included 5 CGM applications, a full-season weed-free (hand-weeded) treatment, a full-season weedy-check, a partial-season weed-free (weed-free for the first half of the growing season), and a weedy-check without onions. Corn gluten meal was applied at 4 rates (1000, 2000, 3000, and 4000 kg/ha) plus a full-season hand-weeded treatment combined with a 4000 kg/ha CGM application. Visual crop injury, weed control ratings, and onion yields were evaluated. The highest CGM rate (4000 kg/ha) maintained 72.1% total weed control and 82.7% broadleaf weed control until 46 days after planting. Although the CGM applications did not produce visual phytotoxic symptoms or any reductions in bulb production, the large and total marketable yields were less for the CGM weed-free treatment than the full-season weed-free treatment. The reduction in onion yields for the CGM weed-free treatment compared to the full-season weed-free indicate that CGM had a negative impact on spring-transplanted onion growth. Increased weed competition caused a downward shift in bulb size distribution across the four bulb categories (colossal, large, medium, and small). This research demonstrated that corn gluten meal can provide moderate weed control for spring-transplanted onions, but supplemental weed control is required to maximize onion yields.