Optimizing Agronomic Production of Winter Canola for Plant Growth and Winter Survival

Jesse Warren Ford

doi:10.7273/000005246

Producers of winter canola (Brassica napus L.) can face challenges of poor stand establishment and winter survival in the inland Pacific Northwest (iPNW). Poor rates of stand establishment and winter survival lead to unsatisfactory yields and insufficient economic performance. Improving stand establishment and winter survival of winter canola in the iPNW region will likely increase the attractiveness of including winter canola in cropping system rotations. Producers in the iPNW region face disease and weed pressure in the cereal dominant crop rotations common to the region. Canola provides an opportunity for producers to diversify their cropping rotations and utilize a broader range of integrated pest management practices. Winter canola is a more desirable alternative than spring canola for the intermediate and low rainfall regions of the iPNW for multiple reasons. Winter canola has a longer growing season that utilizes precipitation more efficiently and winter canola flowers earlier than spring canola avoiding periods of high temperatures that can inhibit yield production. Finally, winter canola provides higher yields than spring canola. This research discusses factors related to the issues of stand establishment and winter survival. These factors are the prediction of winter survival based on physical plant dimensions, the use of gibberellin inhibitors to inhibit plant growth, and exploring seeding dates and rates for optimum agronomic performance. A crown height less than two centimeters (cm), a crown width greater than one cm, a canopy width greater than 24 cm, and a leaf count of six or more leaves were all individual predictors associated with high rates of survival. A general linearized model was utilized to predict winter survival of winter canola and a model predictive success rate of nearly 87 percent was achieved. A hypothesis that gibberellic acid (GA) inhibitors could be used to limit excessive plant growth of early planted canola was tested and it was found that foliar application of paclobutrazol and tebuconazole was largely ineffective for managing plant growth. Significant but inconsistent positive yield responses were observed with GA inhibitor application. Earlier seeding dates have a significant positive correlation to larger plant size in both years of this research. July 15th and July 30th planting dates had significantly greater yields than the August 16th planting date for the 2021-2022 growing season, with July 30th yielding significantly more than July 15th and August 16th. Seeding rate did not have a significant impact on yield but did have a significant effect on plant size. Increasing seeding rate was negatively correlated with plant size. Further research examining the optimal seeding dates and rates for winter canola will lead to better recommendations for stand establishment and winter survival. This can be done by improving timing recommendations for seeding into a shallow moisture line, reducing luxury water consumption, and optimizing plant growth for successful overwinter. Further research is needed to understand what benefits foliar applied GA inhibitors may offer to canola production in this region.

Optimizing Agronomic Production of Winter Canola for Plant Growth and Winter Survival

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