Does genotypic variation in nitrogen remobilisation efficiency contribute to nitrogen efficiency of winter oilseed-rape cultivars (Brassica napus L.)?

摘要

Winter oilseed-rape production is characterized by a low N efficiency, due to low N uptake and insufficient N remobilisation to the seeds. In particular, a reduction of leaf N losses might be one way to improve N efficiency of this crop. It was tested if variations in leaf N losses and in stem residual N amounts at maturity exist between cultivars differing in N efficiency. In a 3-year field experiment, four oilseed rape cultivars were cultivated at limiting, medium, and high N supply. N harvest indices in this study were comparatively high (around 0.79) and leaf N losses amounted to at most 13 kg N ha(-1). 86 % of the leaf N present at the beginning of flowering was remobilised, irrespective of N rate or cultivar. Nevertheless, genotypic variation in leaf N loss existed. They were mainly due to differences in leaf N accumulation until flowering. Residual N in stems (up to 33 kg N ha(-1)) was higher than leaf N losses and varied more between treatments but was not related to genotypic variation in yield. N uptake after flowering was more important than N remobilisation from vegetative biomass for genotypic variation in seed yield both at low and high N supply.