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Title: Racer (Ammonium Nonanoate) weed control evaluation for onions

Author
item Webber Iii, Charles
item SHREFLER, JAMES - Oklahoma Agriculture Experiment Station
item BRANDENBERGER, LYNN - Oklahoma State University

Submitted to: Extension Publications
Publication Type: Experiment Station
Publication Acceptance Date: 1/29/2010
Publication Date: 2/23/2010
Citation: Webber III, C.L., Shrefler, J.W., Brandenberger, L.P. 2010. Racer (Ammonium Nonanoate) weed control evaluation for onions. 2009 Weed Control Report. Oklahoma State University, Division of Agricultural Sciences and Natural Resources, Department of Horticulture and Landscape Architecture. Stillwater, OK. MP-162 p. 5-8.

Interpretive Summary: Organic onion producers need organic herbicides that can effectively provide post-emergent weed control. Racer is a potential herbicide for organically grown food crops. Weeds reduce crop yields, increase production costs, and can be hosts for crop diseases and detrimental insects. All components entering into the organic crop production system must be approved for organic use, including herbicides. The main component (40%) of Racer is ammonium nonanoate (ammonium pelargonate), which occurs in nature and primarily formed from biodegradation of higher fatty acids. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine effects of application rate and broadcast application of Racer on weed control efficacy, crop injury, and yields. Intermediate day, sweet onion cvs. 'Candy' and 'Cimarron' were transplanted on March 20, 2009 into 2 rows per 6 ft-wide raised beds. Each plot consisted of two onion rows per 10 ft length of bed. The experiment included 8 weed control treatments (3 application rates at 2 hand-weeding levels, plus an untreated weedy-check and an untreated weed-free) with 4 replications. Broadcast applications of Racer at 7.5 produced poor (70% or less) broadleaf weed control, while Racer at 10 and 15% provided excellent (greater than or equal to 90%) total broadleaf weed control through 10 DAT. Onion injury increased as Racer application rate increased with no significant difference among treatments at 18 DAT. Crop injury and lack of weed control from Racer reduced yields compared to the untreated weedy-check. If the Racer's application method can be modified to reduce crop injury, the higher application rate has potential to make significant impact on broadleaf weed control in spring-transplanted onions.

Technical Abstract: Racer has been labeled as a herbicide for food use and is currently under consideration as an organic herbicide for organically grown food crops. The main component (40%) of Racer is ammonium nonanoate (ammonium pelargonate), which occurs in nature and primarily formed from biodegradation of higher fatty acids. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine effects of application rate and broadcast application of Racer on weed control efficacy, crop injury, and yields. Intermediate day, sweet onion cvs. 'Candy' and 'Cimarron' were transplanted on March 20, 2009 into 2 rows per 6 ft-wide raised beds. Each plot consisted of two onion rows per 10 ft length of bed. The experiment included 8 weed control treatments (3 application rates at 2 hand-weeding levels, plus an untreated weedy-check and an untreated weed-free) with 4 replications. Broadcast applications of Racer at 7.5 produced poor (70% or less) broadleaf weed control, while Racer at 10 and 15% provided excellent (greater than or equal to 90%) total broadleaf weed control through 10 DAT. Onion injury increased as Racer application rate increased with no significant difference among treatments at 18 DAT. Crop injury and lack of weed control from Racer reduced yields compared to the untreated weedy-check. If the Racer's application method can be modified to reduce crop injury, the higher application rate has potential to make significant impact on broadleaf weed control in spring-transplanted onions.