Effects of reduced plant height on breeding requirements and ...

would be useful to know the rerative contribution <strong>of</strong> the
various yield components to the result. This infornation
would be <strong>of</strong> help to the breeder in selectíng parental
¡nateriaL and in selecting within and. among segregatj.ng
populations.
At all sites, as applied N increased, so did the number
<strong>of</strong> spikes per unit area; with the initial incrernent <strong>of</strong> N
giving the greatest response. This was partic ularly the
case at Carman in both years, where moisture stress and weed
cornpetÍtion had rna jor effeets. The further significant
increase due to the upper N increnents at Carnan ín L9?5
probably resulted from improved competition with weed.s in
these treataents. The significant).y greater numbers <strong>of</strong>
spikes per unit area induced by the highest N level_ at
Sanford nay be attributed to a more adequate moÍsture supply.
This resulted in a longer vegetative perlod whj.ch allowed.
more tillers to be produced, survive and. produce spikes. At
these higher N levels at both sites, kernel weight was lower,
and at Sanford the number <strong>of</strong> kernels per head dropped, rela_
tive to the other N treatments.
The genotypes al-l responded similarly to apptied N.
However, t'Uinn64-62 and ClOj!)Z generally had more spikes per
unit area than the ta1ls at all sites. rhis was particularly
the case for Minn64-62. fhe result <strong>of</strong>fers some expranation
for the relatively high yield <strong>of</strong> Minn64-62, particularly as
conpared to the other semi-dwarfs. CZ0IO11 was consistently
the lowest <strong>of</strong> the three in spikes per unit area exeept at
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