A. Kamoshita et al., Grain nitrogen concentration differences among three sorghum hybrids with similar grain yield, AUST J AGR, 50(2), 1999, pp. 137-145
The differences in grain nitrogen (N) concentration among 3 sorghum (Sorghu
m bicolor (L.) Moench) hybrids with similar grain yield were examined under
N-limiting conditions in relation to the availability of assimilate and N
to grain. Several manipulation treatments [N fertiliser application, lower
leaves shading, thinning (reduced plant population), whole canopy shading,
canopy opening, spikelet removal] were imposed to alter the relative N and
assimilate availability to grain under full irrigation supply. Grain N conc
entration increased by either increased grain N availability or yield reduc
tion while maintaining N uptake.
Grain N concentration, however, did not decrease in the treatments where re
lative abundance of N compared with assimilate was intended to be reduced.
The minimum levels of grain N concentration differed from 0.95% (ATx623/RTx
430) to 1.14% (DK55plus) in these treatments. Regardless of the extent of v
ariation in assimilate and N supply to grain, the ranking of hybrids on gra
in N concentration was consistent across the manipulation treatments. For t
he 3 hybrids examined, higher grain N concentration was associated with hig
her N uptake during grain filling and, to a lesser extent, with higher N mo
bilisation. Hybrids with larger grain N accumulation had a larger number of
grains. There was no tradeoff between grain N concentration and yield, sug
gesting that grain protein concentration can be improved without sacrificin
g yield potential.