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United States Department of Agriculture

Agricultural Research Service

Research Project: ORGANIC AND REDUCED INPUT FRESH MARKET SPECIALTY CROP PRODUCTION SYSTEMS FOR THE SOUTHERN GREAT PLAINS Title: Organic onions and potential organic herbicides for post-directed applications

Authors
item Webber, Charles
item Shrefler, James -
item Brandenberger, Lynn -

Submitted to: Proceedings of Horticultural Industry Show
Publication Type: Proceedings
Publication Acceptance Date: January 15, 2011
Publication Date: March 28, 2011
Citation: Webber III, C.L., Shrefler, J., Brandenberger, L.P. 2011. Organic onions and potential organic herbicides for post-directed applications. In: Proceedings of Horticultural Industry Show, January 14-15, 2011, Fort Smith, Arkansas. p. 118-122.

Interpretive Summary: Oklahoma producers are interested in sweet onion (Allium cepa L.) as an alternative crop for farm diversification. Onions do not compete well with weeds due to their slow growth rate, short height, non-branching plant structure, low leaf area, and shallow root system. The weed control challenges for onion production are even greater for those considering organic crop production. Organic onion producers need organic herbicides that can effectively provide post-emergent weed control. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the impact of potential organic herbicides on weed control efficacy, crop injury, and yields. The experiment included 12 weed control treatments (5 herbicides at 2 rates, plus an untreated weedy-check and an untreated weed-free) with 6 replications. The 5 herbicides and the rates included Burnout (registered trademark), 15 and 30% volume/volume (v/v), MatranEC (registered trademark), 5 and 7 % v/v, Scythe (registered trademark), 5 and 7%, Racer (registered trademark), 9 and 12.6% v/v, and vinegar, 40 and 80 gpa). Each herbicide was applied on May 20, 2009 and then reapplied after an 8 day interval between applications. Intermediate day, sweet onions, cv. '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 post-directed application of MatranEC produced the highest onion yields among the herbicides, although not significantly greater than the weedy-check. Sequential-applications significantly increased weed control when comparing weed ratings at 7 days after the first herbicide application and 1 day after the second application. Scythe, Racer, and vinegar produced the best weed control at the application rates used in this study. Although onion injury was reduced compared to previous research with the over-the-top broadcast applications of these herbicides, the application timing needs to be improved to control the weeds at earlier growth stages and provide virtually weed-free conditions from the point of onion transplanting through harvest.

Technical Abstract: Organic onion producers need organic herbicides that can effectively provide post-emergent weed control. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the impact of potential organic herbicides on weed control efficacy, crop injury, and yields. The experiment included 12 weed control treatments (5 herbicides at 2 rates, plus an untreated weedy-check and an untreated weed-free) with 6 replications. The 5 herbicides and the rates included Burnout (registered trademark), 15 and 30% volume/volume (v/v), MatranEC (registered trademark), 5 and 7 % v/v, Scythe (registered trademark), 5 and 7%, Racer (registered trademark), 9 and 12.6% v/v, and vinegar, 40 and 80 gpa). Each herbicide was applied on May 20, 2009 and then reapplied after an 8 day interval between applications. Intermediate day, sweet onions, cv. '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 post-directed application of MatranEC produced the highest onion yields among the herbicides, although not significantly greater than the weedy-check. Sequential-applications significantly increased weed control when comparing weed ratings at 7 days after the first herbicide application and 1 day after the second application. Scythe, Racer, and vinegar produced the best weed control at the application rates used in this study.

Last Modified: 9/1/2014
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