Response of herbicide-tolerant canola (Brassica napus L.) cultivars to four row spacings and three seeding rates in a no-till production system

Appropriate management practices are important to reduce input costs and to optimize yield and crop quality. The objective of this study was to determine the optimum row spacing (23, 31, 46 and 61 cm) and seeding rate (3.2, 6.4 and 9.6 kg ha(-1) or 87, 173 and 260 seeds planted m(-2)) for two herbicide-tolerant canola (Brassica napus L.) cultivars (an open-pollinated and a hybrid) under a no-till production system. Plant density and yield varied with row spacing, with the effect being linear in both cases. Plant density decreased with wider row spacing, from 112 plants m(-2) at the 23-cm row spacing to 83 plants m(-2) at the 61-cm row spacing. Yield decreased with wider row spacing, from 2397 kg ha(-1) at the 23-cm row spacing to 2138 kg ha(-1) at the 61-cm row spacing. Results from this study indicate that herbicide-tolerant cultivars of canola grown in no-till production systems under conditions of adequate soil fertility, effective weed management, minimal disease pressure, and good flea beetle control, produced the highest plant densities and yields at row spacing of 24-31 cm, that seeding rates in the range of 3.2-9.6 kg ha(-1) had no effects on yield, and that a hybrid cultivar performed better than open-pollinated cultivars in terms of plant density, earliness and duration of flowering, and seed size. The study helps to better define the response of plant density and seed yield in herbicide-tolerant canola cultivars to changes in row spacing and seeding rate. In particular, the results of this study suggest that plant density may not be a reliable predictor of canola yield, although row spacing is an important consideration.