Overcoming seed dormancy in oilseed rape ( Brassica napus L .) with exogenous compounds

Summary Dormant seeds of oilseed rape ( OSR ) can persist in the soil and cause OSR volunteers in subsequent crops. Several approaches were tested in the laboratory and in the field to determine whether dormancy induction and seed persistence can be reduced by using dormancy‐breaking exogenous compounds. In a laboratory experiment, OSR seeds were coated with KNO 3 , micronutrients, or gibberellic acid ( GA ) prior to a secondary dormancy test. In a field experiment, seeds were coated in a manner analogous to the laboratory experiment, and then buried 10 cm deep in the soil for 2.5 months. In a practical demonstration, OSR plants were sprayed with either urea ammonium nitrate ( UAN ) or a commercial product containing GA prior to seed maturity. Seed coating (laboratory and field experiments) reduced secondary dormancy and seed persistence in the field by up to 99%. The efficiency of the treatments for mitigating secondary dormancy (laboratory and field experiments) in decreasing order was GA  > micronutrients > KNO 3 > control. With pre‐maturity spraying (practical demonstration), UAN reduced primary dormancy by up to 77% and the development of secondary dormancy by up to 38%; GA had no effect. Dormancy and seed persistence of OSR seeds may be reduced by a pre‐maturity UAN treatment of OSR mother plants, or by applying appropriate exogenous compounds to OSR seeds.