ARS | Publication request: Over-the-top broadcast applications of Racer® on onion weed control, crop injury, and yields

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. Over-the-top broadcast applications of Racer® on onion weed control, crop injury, and yields. In: Proceedings of Horticultural Industry Show, January 14-15, 2011, Fort Smith, Arkansas. p. 113-117.

Interpretive Summary: The weed control challenges for onion production are formidable; however, these challenges are even greater for those considering organic crop production. Organic onion producers need organic herbicides that can effectively provide post-emergent weed control. Racer (registered trademark) (40% ammonium nonanoate) is a potential herbicide for organically grown food crops. Ammonium nonanoate occurs in nature and is primarily formed from biodegradation of higher fatty acids. Research was conducted in southeast Oklahoma to determine the effect of application rates and broadcast application of Racer on weed control efficacy, crop injury, and yields. Intermediate day, sweet onions, cvs. 'Candy' and 'Cimarron,' were transplanted on March 20, 2009. 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 check) with 4 replications. Broadcast applications of Racer at 7.5 resulted in 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 in injury ratings among treatments at 18 DAT. Crop injury and lack of weed control from Racer reduced crop 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 (registered trademark) (40% ammonium nonanoate) is a potential herbicide for organically grown food crops. Ammonium nonanoate occurs in nature and is primarily formed from biodegradation of higher fatty acids. Research was conducted in southeast Oklahoma to determine the effect of application rates and broadcast application of Racer on weed control efficacy, crop injury, and yields. Intermediate day, sweet onions, cvs. 'Candy' and 'Cimarron,' were transplanted on March 20, 2009. 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 check) with 4 replications. Broadcast applications of Racer at 7.5 resulted in 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 in injury ratings among treatments at 18 DAT. Crop injury and lack of weed control from Racer reduced crop 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.