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Agronomic traits contributing to nitrogen efficiency of winter oilseed rape cultivars

Schulte auf‘m Erley, Gunda, Behrens, Torsten, Ulas, Abdullah, Wiesler, Franz, Horst, Walter J.
Field crops research 2011 v.124 no.1 pp. 114-123
Brassica napus var. napus, agronomic traits, cultivars, environmental factors, fertilizer rates, field experimentation, harvest index, nitrogen, nitrogen content, seed yield, seeds, shoots, surpluses, vegetative growth
Reducing the high nitrogen (N) balance surpluses occurring in oilseed rape production through the cultivation of N-efficient cultivars is imperative for environmental reasons. In this study, seed yield and N efficiency parameters of oilseed rape cultivars grown under three N rates were investigated in field experiments performed during five years. Seed yields differed significantly among cultivars especially at limiting N supply, with significant shifts in cultivar ranking according to the N level. At high N supply, cultivar differences relied more on year effects. The importance of N efficiency parameters for yield varied owing to year and N rate effects. N uptake was an important parameter for yield at all N rates. While at low N, the duration of N uptake was most decisive, shoot N uptake capacity during vegetative growth was relatively more important under high N conditions. N utilization efficiency became more important with increasing N supply. At high N supply, cultivars with low seed N concentrations were superior in yield. Harvest index was also significantly correlated to yield across N rates; however, its importance depended much on environmental conditions. In conclusion, the specification of plant traits that might contribute to enhanced N efficiency in oilseed rape will depend very much on the N supply of the target environment and the target yield level.