Nitrogen dynamics in field grown oilseed rape. Effect of nitrogen fertilization and genotype

摘要

Despite a high nitrate uptake capacity, the nitrogen use efficiency (NUE) of oilseed rape is weak due to a relatively low N remobilization from vegetative (mostly leaves) to growing parts of the plant Thus, this crop requires high rate of N fertilization and leaves fall with high N content. In order to reduce the rate of N fertilization and to improve the environmental impact of oilseed rape without decreasing yield, it is crucial to better understand the dynamics of N through the plant. This study presents the effect of contrasted N fertilizations and genotypes on the N dynamics of oilseed rape grown under field conditions. The experiment was conducted in a field-grown winter oilseed rape under three levels of N dose (0, 100 and 200 kg N ha-1)and three genotypes (cv. 'Capitol', 'Pollen' and 'Saturnin'). Plants were sampled frequently from stem extension (GS 2,4) to maturity (GS 9,9) by using a 15N labelling technique in order to distinguish in each tissue N coming from uptake or remobilization. N fertilization increased biomass and N accumulation whatever the genotype. The partitioning of N taken up was affected by N fertilization and genotype, whereas N uptake decreased during flowering irrespective of N fertilization and genotype. Whatever the N treatment and the genotype, more than 60% of pods N came from N rernobilization ofvegetative tissues, green leaves being the main source of remobilized N. The timing and the part of N remobilized from the different vegetative organs depended on the N supply and cultivar. The efficiency ofN remobilization in leaves increased with the rate of N fertilization and along an axial gradient from the basal to the uppermost leaves. Better synchronising leaf N remobilization and grain filling could improve the NUE of oilseed rape.