Comparative nitrogen response and economic evaluation for optimum yield of hybrid and open-pollinated canola

Abstract

Plant breeders have dramatically improved the yield potential of new canola cultivars. To achieve optimum yield with such cultivars, particularly hybrids, may require changes to fertilizer management practices that were established prior to development of these cultivars. We investigated the influence of N fertilizer rate (0, 30, 60, 90, 120, and 150 kg N ha-1) on plant density, days to flowering, length of flowering stage, days to maturity, biomass, seed yield and quality, and economic returns of two canola cultivars (Quantum, a high-yielding open-pollinated; and InVigor® 2663, a high-yielding hybrid) on a Dark Brown (Scott), a Thick Black (Melfort), and a Thin Black (Indian Head) Chernozem soil in Saskatchewan in 2000 and 2001. Plant density was slightly lower for InVigor 2663 than Quantum due to larger seed size of the former. InVigor 2663 tended to take more days to flowering and had shorter flowering stage duration compared with Quantum, but the two cultivars showed no consistent difference for the number of days to maturity. InVigor 2663 generally produced more biomass and seed yield than Quantum. Oil and protein concentration in seed were higher for InVigor 2663 than Quantum, with an opposite trend for the proportion of green seeds, indicating better seed quality for InVigor 2663. Addition of N tended to reduce plant density and decreased seed oil concentration, while it increased crop growth duration, seed protein concentration, seed yield and biomass. Under adequate N fertilization, InVigor 2663 provided greater net economic returns than Quantum under both moist and relatively dry conditions. In conclusion, InVigor 2663 performed better agronomically than Quantum, but the similar nature of seed yield response to applied N suggests that target N fertilizer rates for optimum seed yield and net economic returns should be similar for both cultivars based on this limited comparison of one hybrid and one open-pollinated canola cultivar under these soil-climatic conditions. Key words: Brassica napus L., hybrid canola, N rate, open-pollinated canola, seed quality, seed yield