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Title: Weed control alternatives for spring transplanted onions

item Webber Iii, Charles

Submitted to: National Allium Research Conference
Publication Type: Abstract Only
Publication Acceptance Date: 11/9/2004
Publication Date: 12/8/2004
Citation: Webber III, C.L., Shrefler, J.W. 2004. Weed control alternatives for spring transplanted onions [abstract]. National Allium Research Conference. p. 63.

Interpretive Summary:

Technical Abstract: Sweet onion (Gallium cape L.) producers need additional options for controlling weeds within spring transplanted onions. As interest in sweet onion production has grown, so has the realization that uncontrolled weeds can result in a total loss of marketable onion production. Although mechanical weed control can successfully control weeds between rows, producers need reliable methods for controlling the weeds within the crop row between the onions. Two years (2002 and 2003) of field research was conducted in southeast Oklahoma (Lane, OK) to determine the efficacy of inorganic and organic herbicides for use on spring transplanted onions. Twenty-one weed control treatments, including both inorganic (pendimethalin and oxyfluorfen) and organic (Corn Gluten Meal) herbicides, were applied to spring transplanted 'Hybrid Yellow Granex PRR' onions planted in two rows, 91 cm inches apart, on raised beds. The herbicide treatments included pendimethalin applications at 0.5 kg ai/ha, 1.0 kg ai/ha, and 1.5 kg ai/ha, oxyfluorfen at 0.1 kg ai/ha, 0.2 kg ai/ha, and 0.3 kg ai/ha, and tank mixes with the herbicides pendimethalin and oxyfluorfen at each rate. Corn Gluten Meal (CGM) was applied by hand, spreading the dry material at 4 rates (100 g/m**2, 200 g/m**2, 300 g/m**2, and 400 g/m**2). The experiment also included a series of weedy-checks and weed-free treatments to serve as experimental controls. The experiment had very high weed pressure with multiple species of broadleaf and grass weeds. CGM treatments were ineffective in controlling weeds, resulting in the greatest grass and broadleaf dry matter yields, and the lowest total marketable onion yields. Treatments receiving pendimethalin (pendimethalin or pendimethalin + oxyfluorfen) resulted in a greater percent grass control and an increase in marketable onion yields compared to the weedy-check. Select weed control treatments did shift the weed composition compared to the percent grass and broadleaf cover within the weedy-check. As the grass weeds were controlled by pendimethalin, the broadleaf weeds compensated by increasing their growth. The yield advantage for pendimethalin was probably the result of early season weed control that was not apparent at harvest.