Use of Late-Season Herbicides on Winter Canola (Brassica napus) and Its Impacts on Yield and Seed Quality
Bodnar, Victor Ricardo
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Canola (Brassica napus L.) was adopted in the Southern Great Plains as a means to increase the productivity and decrease weed pressure in traditional monoculture wheat. While canola has been effective at achieving this task, the difficulty to apply herbicides in the spring following dormancy can result in high weed pressure within the canola system and potentially the successive wheat crop. Herbicide applications during or around flowering are often prohibited as they have been linked to decreased viability of pollen. However, this information has not been strictly noted in Southern Great Plains. To evaluate this phenomenon in the Southern Great Plains region a trial was initiated at the Cimarron Research Station in Perkins, OK from 2014-2016. Experimental design was a three factorial randomized complete block design with four replications. Factor one was herbicide: glyphosate, quizalofop, and clethodim, factor two being the high or low rate, based on labeled rates, and factor three was canola growth stage: bolting, early flower, and mid flower. Overall, the application of herbicides during reproductive growth negatively affected crop yield. Also, it was especially true for glyphosate, which decreased yields by an average of 389, 483, and 182 kg ha-1 during bolting, early flower, and mid flower, respectively. Higher herbicide application rates usually resulted in decreased yield, but was only statistically significant with the glyphosate applications. Seed quality was significantly decreased; in a similar way to the yield. These results suggest that late-season herbicide applications, especially glyphosate, should be avoided when possible as decreased yield and seed quality can be expected.
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