Comparing Brassica oilseed crop productivity under contrasting N fertility regimes in the semiarid northern Great Plains

Miller, P. R., Angadi, S. V., Androsoff, G. L., McConkey, B. G., McDonald, C. L., Brandt, S. A. Cutforth, H. W., Entz, M. H. and Volkmar, K. M. 2003. Comparing Brassica oilseed crop productivity under contrasting N fertility regimes in the semiarid northern Great Plains. Can. J. Plant Sci. 83: 489-497. We compared the growth and yield of five Brassica spp. genotypes [two B. juncea (L.) Coss., two B. napus L. and one B. rapa L.]in 11 environments spanning two degrees of latitude and longitude in southern Saskatchewan in 1996-1998. All entries were managed with three levels of N fertility at each site. Plant height for the canola-quality B. juncea breeding line J904316 was 21% greater than the mean of the other genotypes, but shoot biomass did not differ for the same comparison. Cutlass Oriental mustard consistently yielded greatest across all environments while the yield of J904316 was highly variable among environments. The mean seed yield of Cutlass was 12% greater than the highest-yielding B. napus cultivar and 32% greater than the B. rapa cultivar, and had a greater harvest index. Earlier genotypes yielded greater than late-flowering and maturing genotypes within B. juncea and B. napus, but the earliest genotype, Maverick (B. rapa), yielded lower than all other genotypes. All Brassica spp. genotypes were responsive to N fertilization, and high total available N (average = 109, range = 91 to 131 kg N ha(-1)) was generally required to maximize seed yield, but not shoot biomass, under the conditions of this study. Pod density was the primary yield component influenced by N level. This study illustrates the potential adaptive advantage of B. juncea on the semiarid northern Great Plains.