Comparative growth analysis of Brassica napus and Brassica juncea under Swedish conditions

Indian cultivars of Brassica juncea were tested in field experiments at the research farm of the Swedish University of Agricultural Sciences, Uppsala, to determine their agronomic performance under Swedish climatic conditions. In this study, production and development of a B. juncea cultivar of Indian origin and a Swedish B. napus cultivar were compared in a growth analysis during 1987-1990. Plants were harvested at approximately weekly intervals from emergence to maturity, and separated into leaves, stems, pods and seeds. Area indices of leaves, stems and pods were calculated, and dry weight of each plant component was determined. On an average of 4 yr, the total growing period was similar for both cultivars, 107 d or ca. 1030 growing degree days (GDD), with an earlier onset and a shorter duration of flowering for B. juncea. Dry weights of all vegetative plant components, especially stems, reached higher maximum levels in the highly branched B. juncea cultivar than in the B. napus cultivar. By the end of the flowering stage, B. napus had accumulated a significantly higher percentage of final total dry matter than B. juncea. After flowering, the crop growth rate was significantly higher in B. juncea, 0.54 g m-2 GDD-1, than in B. napus. Seed yield level was similar in both species, and in year 1990 ca. 2.2 t ha-1 was harvested.