Effects of nitrogen fertilizer application on seed yield, N uptake, N use efficiency, and seed quality of Brassica carinata

Ethiopian mustard (Brassica carinata A. Braun) is a relatively new crop in western Canada and research information on its response to N fertilizer is lacking. Two field experiments (exp. 1 at 3 site-years and exp. 2 at 4 site-years) were conducted from 2008 to 2010 in Saskatchewan and Alberta, Canada, to determine effect of N fertilizer application on Brassica carinata plant density, seed and straw yield, N uptake in seed and straw, N use efficiency (NUB), N fertilizer use efficiency (NFUE) and seed quality. N rates applied were 0 to 160 kg N ha(-1) and 0 to 200 kg N ha(-1) in exps. 1 and 2, respectively. Plant density was not affected by increasing N rate at 5 site-years but declined with high rates of N application at 2 site-years. Seed yield responded to applied N in 6 of 7 site-years, with the non-responsive site having a high total N uptake at the 0 kg N ha(-1) rate (high N-t value). There were no sites where seed yields were maximized with the N rates applied. Response trends of straw yield and N uptake were similar to that of seed yield at the corresponding site-years. NUE and NFUE generally declined as N rate increased. Protein concentration in seed generally increased and oil concentration in seed decreased with increasing N rates. In conclusion, the responses of seed yield, total N uptake, NUB, and NFUE to applied N was similar to those reported in other Brassica species with the exception that a rate was not identified in which Brassica carinata yields were maximized.