The Effects of Nitrogen Rates on Plant Properties and Arthropod Visitation of Three Winter Canola (Brassica napus L.) Cultivars in Tennessee

Winter canola production has increased in the United States over the past several decades however, there is a lack of research in the southeastern United States on agronomic production, growth characteristics, and pollinator habitat use of winter canola. The objectives of this study sought to determine the effects of different nitrogen (N) fertilizer rates on winter mortality, yield, oil and protein meal content, seed pod shatter resistance, and pollinator use across three different cultivars. Canola was grown in a randomized split complete block design with four replicates under five different N rates (0, 56, 112, 168, 224 kg N ha-1) with three different cultivars (Hekip, Inspiration, and Edimax CL/Phoenix CL). Seed yield was low (306.4 kg ha-1) for the 2017/2018 season and no significant differences were observed between treatments. In spring 2018, Edimax CL had significantly lower mortality (79.7%) than Inspiration (85.7%) and Hekip (83.9%). Shatter resistance varied by cultivar and N treatment and higher N rates led to a greater shatter index. A significant difference between N rates and oil content was detected in my study. Rates 0 and 56 kg N ha-1 were statistically different than 224 kg N ha-1. Protein content was significantly different at N rates of 0 (19.9%) and 224 kg N ha-1 (21.4%). A temporal relationship of pollinator species visiting winter canola cultivars over the eight-week period in response to flowering was observed. Honey bees were captured throughout the flowering period, while native mining bees had high abundance early in the study. Mining bee populations declined as N rates increased for the cultivars Inspiration (R2 = 0.95) and Edimax CL (R2 = 0.70) from averages of 4,000- 5,500 to 2,000- 3,000 bees ha-1. I detected a significant difference in pollinator diversity from cultivars Hekip and Edimax CL at N rates of 224 kg ha-1 and 56 kg ha-1. Inspiration may be the best cultivar based on my data due to its greater soil coverage, good emergence, and lower required N. My findings on pollinator diversity also provide a record base for the diversity of arthropods that are potentially utilizing winter canola in the region