Acetic acid: Crop injury and onion (Allium cepa L.) yields

Authors: Webber Iii, Charles; SHREFLER, JAMES - OSU, LANE, OK

Submitted to: National Allium Research Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/15/2009
Publication Date: 2/7/2009
Citation: Webber III, C.L., Shrefler, J.W. 2009. Acetic acid: Crop injury and onion (Allium cepa L.) yields. 2008 National Allium Research Conference, December 10-13, 2008, Savannah, Georgia. p.55-59.

Interpretive Summary: Onions (Allium cepa L.) are not very competitive with weeds due to its plant structure, low leaf area, and slow growth rate. Organic herbicides for sweet onions are limited to non-selective materials, such as corn gluten meal and vinegar. Research at Lane, Oklahoma has shown that corn gluten meal can be an affective early season pre-emergence herbicide for onion transplants, but once the residual impact of the corn gluten meal wears off, the resulting weed growth can cause total loss of the onion crop. Post-emergence application of vinegar has the potential to control weeds emerging after corn gluten meal applications, but the extent of crop injury from broadcast applications of vinegar is unknown. Research was conducted at Lane to determine the impact of a broadcast application of acetic acid on onion crop injury. The experiment included 2 onion varieties ('Candy' and 'Cimarron'), 6 treatments (2 application volumes, 2 hand weeding levels, plus an untreated weedy-check and an untreated weed-free) with 4 replications. Vinegar (20% acetic acid) was applied as an over-the-top broadcast application at either 50 or 100 gpa using four 8002 nozzles on 20 inch spacing. Within each application volume (50 and 100 gpa) plots were either handweeded, or uncontrolled weeds were allowed to grow. Crop injury ratings were collected throughout the growing season. The greatest onion injury was observed at 3 days after treatment (DAT), resulting in 38% onion injury for the 50 gpa rate and 56% for 100 gpa rate. There were no significant differences between onion varieties for injury. The results indicate that the early season crop injury did not significantly impact onion yields.

Technical Abstract: Weed control is a major challenge in conventional and organic production systems, especially for organically produced sweet onion (Allium cepa L.). Organic herbicides for sweet onions are limited to non-selective materials, such as corn gluten meal and vinegar. Research at Lane, Oklahoma has shown that corn gluten meal can be an affective early season pre-emergence herbicide for onion transplants, but once the residual impact of the corn gluten meal wears off, the resulting weed growth can cause total loss of the onion crop. Post-emergence application of vinegar has the potential to control weeds emerging after corn gluten meal applications, but the extent of crop injury from broadcast applications of vinegar is unknown. Research was conducted at Lane to determine the impact of a broadcast application of acetic acid on onion crop injury. The experiment included 2 onion varieties ('Candy' and 'Cimarron'), 6 treatments (2 application volumes, 2 hand weeding levels, plus an untreated weedy-check and an untreated weed-free) with 4 replications. Vinegar (20% acetic acid) was applied as an over-the-top broadcast application at either 50 or 100 gpa using four 8002 nozzles on 20 inch spacing. Within each application volume (50 and 100 gpa) plots were either handweeded, or uncontrolled weeds were allowed to grow. Crop injury ratings were collected throughout the growing season. The greatest onion injury was observed at 3 days after treatment (DAT), resulting in 38% onion injury for the 50 gpa rate and 56% for 100 gpa rate. There were no significant differences between onion varieties for injury. The results indicate that the early season crop injury did not significantly impact onion yields.