Controlling the Overwintering Capacity of Winter Canola Using Plant Growth Regulators to Manage Fall Growth.

Canola (Brassica napus L.)  production in the Southern Great Plains is limited by the overwintering capacity of the crop.  Planting date and plant growth regulators (PGRs) were evaluated in winter canola to control fall growth and improve overwintering capacity. Field experiments were conducted at four sites across Oklahoma in 2015-2016 to evaluate the impact of planting date paired with the use of plant growth regulators (PGR) on stand establishment, winter hardiness, and yield for winter canola.  

Experiments were conducted in a strip block design with a factorial treatment structure. Treatments included 1) a control plot for each planting date that received no PGR treatment, 2) tebuconazole at 63.07 g ai ha^-1; 3) tebuconazole at 126.15 g ai ha^-1; 4) mepiquat chloride at 12.27 g ai ha^-1; 5) mepiquat chloride at 24.53 g ai ha^-1; 6) mepiquat pentaborate at 57.47 g ai ha^-1; 7) prohexadione-calcium at 139.75 g ai ha^-1; 8) metconazole at 52.56 g ai ha^-1 and 9) kinetin/gibberellic acid/indole butyric acid at 2.25 g ai ha^-1, 0.841 g ai ha^-1, and 1.12g ai ha^-1.  Planting dates began August 25^th and were sequential every week for five weeks.  PGR applications were made at the four to six leaf stage.  Stand counts were taken at application and again 4WAT with height and biomass. Yield, protein and oil content were recorded at harvest.

PGR had no effect on yield, protein or oil content.  However, planting date impacted stand count and all three yield components. DKW 44-10 planted September 7^th-30^th produced yields 10.8- 14.5% greater than canola planted earlier. Stand establishment was best for canola planted September 23-30^th.  PGR did influence plant height with an 11% reduction when treated with 51.3 g a.i. ha^-1 metconazole compared to the nontreated. Oil content was 1% higher when planted Aug 25^th; however, it was not high enough for a producer to realize a premium for the crop. This work was funded by the Oklahoma Oilseed Commission and USDA-NIFA.