Nitrogen fertilizer is a major input cost in canola ( Brassica napus L.) production and farmers are interested in improving N use efficiencies. A multi-site study in western Canada was conducted to determine the merits of polymer-coated urea (Environmentally Smart Nitrogen, ESN) compared with urea on weed management and yield of hybrid and open-pollinated (OP) canola. Treatments included a hybrid and OP canola cultivar, ESN and urea, 100 and 150% of soil test N fertilizer rates, and 50 and 100% of registered in-crop herbicide rates. Canola was grown in rotation with barley ( Hordeum vulgare L.) in a no-till system and both crops of the rotation were present each year. Fertilizer and herbicide rate treatments were applied to the same plots in four consecutive years to determine annual and cumulative effects. Hybrid compared with OP canola reduced weed tissue N concentration in 40% of the cases and reduced weed biomass in 80% of the cases. Additionally, weed tissue N concentration was lower with ESN than with urea in 70% of the cases, indicating that crop-weed competition for soil N might be reduced if ESN were used. Canola yield was greater for the hybrid cultivar in 15 of 20 site-years. Both cultivars expressed a positive yield response to the 150% N fertilizer rate in 10 of 20 site-years. This yield response occurred in three additional site-years with hybrid canola, indicating that hybrid cultivars have a higher N demand under favorable growing conditions. Canola yield was similar with ESN and urea in 14 of 20 site-years. The ESN compared with urea increased canola yield in 4 site-years and in one additional site-year for hybrid canola, indicating that ESN may be advantageous in some situations. Canola seed oil concentration was similar with ESN and urea in 19 of 20 site-years. Information gained in this study will be used to develop improved fertilization strategies for canola production on the semiarid Canadian prairies.
