Mitteilungen der Gesellschaft für Pflanzenbauwissenschaften Band 23

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Relative N contents remaining in the straw at maturity increased with increasing N
supply (Fig. 1). Most N residues in the straw were found in the stems. In contrast, N
losses by abscised leaves amounted to only 4, 5 and 6% of total N uptake until
maturity at low, medium and high N supply, and were thus considerably lower than
stated in other studies (Malagoli et al., 2005; Gombert et al. 2010).
Cultivars differed in relative N contents in the seeds and in the straw fractions at all
N rates. At low and medium N supply, cv Apex contained relatively less N in the
seeds and more N in the stems compared to the other cultivars. This was coupled to
a high N uptake of this cultivar. In contrast, cv Bristol was characterized by a higher
N allocation to the seeds and low N amounts in the stems and dead leaves at all N
rates. Thus, at high N supply, the improved N retranslocation of this cultivar might
have contributed to its high seed yield in addition to the high N uptake achieved by
this cultivar.
N fraction (%)
100
95
30
25
20
15
10
5
0
N0
a b ab ab
ab
a b ab
b a a a
a a a a
Apex
Bristol
Lirajet
Capitol
dead leaves
stem
pod walls
seeds
100
95
30
25
20
15
10
5
0
N120
a c b bc
b
b
a
a
a a
a a
b a b b
Apex
Bristol
Lirajet
Capitol
100
95
30
25
20
15
10
5
0
N240
a b a b
a
c
a
a
a
a b a
b a b b
Apex
Bristol
Lirajet
Capitol
Fig. 1: Relative N amounts in seeds and straw
fractions of four winter oilseed rape cultivars grown at
three N rates (N0: soil Nmin; N120: 120 kg N ha -1 ; N
240: 240 kg N ha -1 ) in a three-year field experiment
In summary, leaf N remobilisation was found to be very efficient at all N rates and
for all genotypes. Variation in stem N remobilisation was more important for the
amount of N residues. Genotypic differences in stem N remobilisation were found.
Whether these differences were due to genotypic differences in N remobilisation from
the stems or the consequence of differences in yield relative to total N uptake needs
to be further elucidated.
References
Gombert, J. 2010: Effect of nitrogen fertilization on nitrogen dynamics in oilseed rape using 15Nlabeling
field experiment. J. Plant Nutr. Soil Sci. 173:875-884.
Malagoli, M., P. Laine, L. Rossato, A. Ourry 2005: Dynamics of nitrogen uptake and mobilization in
field-grown winter oilseed rape (Brassica napus) from stem extension to harvest. I. Global N flows
between vegetative and reproductive tissues in relation to leaf fall and their residual N. Ann. Bot.
95:853-861.
Schulte auf'm Erley, G., T. Behrens, A. Ulas, F. Wiesler and W.J. Horst 2011: Agronomic traits
contributing to nitrogen efficiency of winter oilseed rape cultivars. Field Crops Res., DOI
10.1016/j.fcr.2011.06.009.