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Title: Impact of corn gluten meal applications on spring-transplanted onion injury and yields

Author
item Webber Iii, Charles
item SHREFLER, JAMES - OSU, LANE, OK
item TAYLOR, MERRITT - OSU, LANE, OK

Submitted to: International Journal of Vegetable Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2007
Publication Date: 12/15/2007
Citation: Webber III, C.L., Shrefler, J.W., Taylor, M.J. 2007. Impact of corn gluten meal applications on spring-transplanted onion injury and yields. International Journal of Vegetable Science. 13(4):5-20.

Interpretive Summary: Herbicide injury and weed competition can produce disproportionate reductions in onion (Allium cepa L.) yields as a result of the onion's slow growth rate, short height, non-branching plant structure, low leaf area, and shallow root system. Field research was conducted in 2002 and 2003 in southeast Oklahoma (Lane, OK) to determine the crop safety and yield response of selected preemergent synthetic herbicides and corn gluten meal (CGM) on spring-transplanted onion production (cv. Hybrid Yellow Granex PRR). The research involved 21 treatments [12 synthetic herbicide treatments, 5 CGM applications, a full-season weed-free (hand-weeded) treatment, a full-season weedy-check, a partial-season weed-free (weed-free for the first half of the growing season), and a weedy-check without onions]. The synthetic herbicide treatments included pendimethalin applications at 0.5, 1.0, and 1.5 kg ai/ha-1, oxyfluorfen at 0.1, 0.2, and 0.3 kg ai/ha-1, and also tank-mixed at these three levels. In addition, the highest rate of each herbicide-pendimethalin (1.5 kg ai/ha**-1), oxyfluorfen (0.3 kg ai/ha**-1), and the tank mix of pendimethalin (1.5 kg ai/ha**-1) plus oxyfluorfen (0.3 kg ai/ha**-1)-were applied and kept weed-free by hand-weeding to determine the crop safety of these herbicides. CGM was applied at 4 rates (1000, 2000, 3000, and 4000 kg/ha**-1). A weed-free (hand-weeded) treatment was also combined with the highest CGM rate (4000 kg/ha **-1) to determine the effect of the GGM on crop injury and growth. Visual crop injury ratings were collected at 3, 5, 10, 20, and 30 days after planting (DAP), along with marketable onion yields by size. No phytotoxic symptoms or yield reductions were observed due to either the synthetic herbicides or CGM applications; therefore, these compounds provided sufficient crop safety when applied at these rates within this production system. Increased weed competition caused a shift in bulb size distribution across the four bulb categories (colossal, large, medium, and small), resulting in a decreased number of colossal and large bulbs and an increase in small bulbs. Although the synthetic herbicides and CGM provided crop safety, and to some extent early weed control, reductions in crop yields as a result of weed competition demonstrated the need to include supplemental weed control with postemergence herbicides or other weed control methods to produce maximum onion yields.

Technical Abstract: Research to determine the relative benefits among alternative herbicides for weed control in onions (Allium cepa L.) should focus not only on weed control efficacy, but also on the impact of the herbicides on crop injury and the resulting weed competition on crop yields. Herbicide injury and weed competition can produce disproportionate reductions in onion yields as a result of the onion's slow growth rate, short height, non-branching plant structure, low leaf area, and shallow root system. Field research was conducted in 2002 and 2003 in southeast Oklahoma (Lane, OK) to determine the crop safety and yield response of selected preemergent synthetic herbicides and corn gluten meal (CGM) on spring-transplanted onion production (cv. Hybrid Yellow Granex PRR). The research involved 21 treatments [12 synthetic herbicide treatments, 5 CGM applications, a full-season weed-free (hand-weeded) treatment, a full-season weedy-check, a partial-season weed-free (weed-free for the first half of the growing season), and a weedy-check without onions]. The synthetic herbicide treatments included pendimethalin applications at 0.5, 1.0, and 1.5 kg ai/ha**-1, oxyfluorfen at 0.1, 0.2, and 0.3 kg ai/ha**-1, and also tank-mixed at these three levels. In addition, the highest rate of each herbicide-pendimethalin (1.5 kg ai/ha**-1), oxyfluorfen (0.3 kg ai/ha**-1), and the tank mix of pendimethalin (1.5 kg ai/ha**-1) plus oxyfluorfen (0.3 kg ai/ha**-1)-were applied and kept weed-free by hand-weeding to determine the crop safety of these herbicides. CGM was applied at 4 rates (1000, 2000, 3000, and 4000 kg/ha**-1). A weed-free (hand-weeded) treatment was also combined with the highest CGM rate (4000 kg/ha**-1) to determine the effect of the GGM on crop injury and growth. Visual crop injury ratings were collected at 3, 5, 10, 20, and 30 days after planting (DAP), along with marketable onion yields by size. No phytotoxic symptoms or yield reductions were observed due to either the synthetic herbicides or CGM applications; therefore, these compounds provided sufficient crop safety when applied at these rates within this production system. Increased weed competition caused a shift in bulb size distribution across the four bulb categories (colossal, large, medium, and small), resulting in a decreased number of colossal and large bulbs and an increase in small bulbs. Although the synthetic herbicides and CGM provided crop safety, and to some extent early weed control, reductions in crop yields as a result of weed competition demonstrated the need to include supplemental weed control with postemergence herbicides or other weed control methods to produce maximum onion yields.