Canola growth, production, and quality are influenced by seed size and seeding rate

Canola (Brassica napus L.) is the most widespread profitable cash crop in Canada. In 2014 and 2015, direct-seeded experiments were conducted in 16 western Canada environments. "Small" canola seed (average 3.32-3.44 g 1000(-1)) was compared to "large" canola seed (average 4.96-5.40 g 1000(-1)) at five seeding rates (50, 75, 100, 125 or 150 seeds m(-2)). Large canola seeds increased crop density and crop biomass but decreased plant mortality, days to start of flowering, days to end of flowering, days to maturity, and percent green seed. Seed size did not influence harvested seed weight, seed oil content or seed protein content. Increasing the seeding rate of small seeds improved canola yield, but the same response did not occur for large seeds. Increasing seeding rates also increased crop density, plant mortality, crop biomass, and seed oil content, but decreased days to start of flowering, days to end of flowering, days to maturity, percent green seed, and seed protein content. Seeding rate had no impact on harvested seed weights. Because higher seeding rates often provide some of the same benefits as large seed, canola growers and the seed industry should balance seed size and seeding rate to obtain the best agronomic performance from canola.