Agronomic Response of Winter Rapeseed to Rate and Date of Seeding

Abstract

AbstractIn northern Idaho, winter rapeseed (Brassica napus L.) usually is seeded on summer fallow in early to mid‐August at 4.5 to 13.5 kg seed ha−1. A 2‐yr study was conducted at Moscow, ID, to quantify crop performance as influenced by date of seeding and seeding rate. In the 1991–1992 and 1992–1993 growing seasons, high‐erucic‐acid winter rapeseed cultivars, ‘Dwarf Essex’ and ‘Bridger’, were seeded on four dates at 2‐wk intervals from early August to mid‐September at four seeding rates from 0.9 to 2.7 × 106 seeds ha−1. Greatest yield for the four dates ranged from 1974 to 2675 kg ha−1. Optimum spring plant stands for attaining those yields were between 61 and 112 plants m−2, obtained at different seeding rates, depending on the date of seeding. The lowest seeding rates (0.9 and 1.5 × 106 seeds ha−1) produced optimum spring plant stands for the mid‐August and early September seeding. Higher seeding rates in early August and mid‐September were necessary to achieve optimum spring plant stands.