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United States Department of Agriculture

Agricultural Research Service

Title: Ammonium pelargonate as a potential organic herbicide

item Webber, Charles - Chuck
item Brandenberger, Lynn
item Shrefler, James
item Wells, Lynda
item Shannon, Kent

Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2008
Publication Date: 6/17/2008
Citation: Webber III, C.L., Brandenberger, L.P., Shrefler, J.W., Wells, L.K., Shannon, K. 2008. Ammonium pelargonate as a potential organic herbicide [abstract]. 2008 Proceeding, Southern Weed Science Society, January 28-30, 2008, Jacksonville, Florida. 61:136.

Interpretive Summary:

Technical Abstract: Weed control is a serious concern for commercial vegetable producers because of the limited number of herbicides available for this group of minor crops and the potential for crop injury. Organic producers of vegetables have an even greater challenge since their weed control tools are limited to cultural methods exclusively. Racer (40% ammonium pelargonate/ammonium nonanoate) is labeled for non-food use and efforts are currently underway to label it as a bio-herbicide for organically grown food crops. The main component of Racer is ammonium pelargonate which occurs in nature and is primarily formed from biodegradation of higher fatty acids. The objective of this study was to investigate impact of application rates and volumes on the weed control efficacy of Racer on endemic weed populations. The field experiment was conducted on fine sandy loam at Lane, OK. The experiment consisted of 9 weed control treatments, which included 2 herbicide rates (7.2 and 10.8 kg/ha) applied at 4 application volumes (164, 327, 655, and 982 L/ha), plus an untreated weedy-check. Racer was applied as a broadcast application using a tractor mounted CO**2 sprayer equipped with four extended range, stainless steel, 1.14 L/min nozzles, on 0.5-m spacings at a spraying height of 0.5 m. To maintain the same spray pattern for each weed control treatment, nozzle pressure was held constant and tractor speed adjusted to achieve the different overall application rates (164, 327, 655, and 982 L/ha). At the time of spraying tumble (Amaranthus albus L.) and spiny (Amaranthus spinosus L. ) pigweed were 2.5-3.8 cm tall, carpetweeds (Mollugo verticillata L.) were 2.5 cm across, and grasses, goosegrass (Eleusine indica L. Gaertn.) and smooth crabgrass [Digitaria isahaemum (Schreb. ex Schweig) Schreb. Ex Muhl.] leaves were 5.1-7.6 cm long. Weeds were rated 6 days after treatment for percent weed control. In general, application of Racer produced greater weed control for the broadleaf weed species (tumble pigweed, spiny pigweed, and carpetweed) than the grass weeds (goosegrass and smooth crabgrass). Although all Racer applications produced significantly greater weed control for all weed species compared to the weedy-check, there were no significant differences among Racer applications for grass weed control. Grass weed control ranged from 30 to 52.5% for goosegrass and 22.5 to 52.50% for smooth crabgrass. The range and magnitude of the broadleaf weed control was much greater than the grass weed control. The best weed control for both pigweed species occurred at the 10.8 kg/ha rate applied at 655 L/ha. Carpetweed was very sensitive to Racer, producing 65% weed control at the lowest application rate and volume, and most application rates and volumes producing at least 85% control. The factorial analysis determined that there were no significant differences among application volumes when averaged across the herbicide application rates. Although not significantly different, there was a tendency for pigweed control to be maximized at the 655 L/ha application volume. Weed control for all weed species was significantly greater for the 10.8 kg/ha application rate compared to the 7.2 kg/ha. Whether comparing the impact of application volume (164, 327, 655, and 982 L/ha) or application rates (7.2 and 10.8 kg/ha), weed control was the greatest for carpetweed compared to either the pigweeds or grass weeds. These results indicate that Racer has an excellent potential as an effective organic herbicide if it achieves the proper clearance. As with other contact herbicides, organic and non-organic, Racer provided greater weed control for broadleaf weeds than grass weeds. It is also important to note that Racer provided consistent control across a large range of application volumes.

Last Modified: 09/21/2017
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