EFFECT OF VARYING SEEDING RATES ON HYBRID AND CONVENTIONAL SUMMER RAPE PERFORMANCE IN MANITOBA

To compare the effects of varying seeding rate on the agronomic performance, phenology and seed quality of hybrid and conventional summer rape cultivars, four hybrid and two conventional summer rape cultivars were seeded at 1.5, 3.0, 4.5, 6.0 and 9.0 kg ha-1 at two locations for 3 yr. The hybrid cultivars were, very importantly, 24% higher yielding and produced 50% more total dry matter than the conventional cultivars. The hybrid cultivars were, on average, 1.3% lower in seed oil content, 1.0% higher in seed protein content and equal in sun of oil and protein in the seed compared with the conventional cultivars. The hybrid cultivars were on average, 1.3 d later to 50% flowering and 1.1 d later to maturity than the average for the conventional cultivars, (i.e., equal or earlier to flowering and maturity than Regent). The hybrid cultivars were also 3.9% lower in harvest index and 1.3 ppm lower in chlorophyll content than the conventional cultivars. In spite of these differences, there were no significant cultivar-by-seedling-rate interactions, indicating that the hybrid and conventional cultivars responded similarly to varying seeding rate. Lodging, days to 50% flowering, days to maturity, harvest index, survival, oil content and protein content displayed significant linear responses to varying seeding rate. Stand at maturity, seed yield and total dry matter production displayed significant linear and quadratic responses to varying seeding rate. Varying seeding rate had no effect on seed formation period, the sum of oil and protein content, or chlorophyll content. A seeding rate of 6 kg ha-1 maximized seed yield for both hybrid and conventional summer rape cultivars.