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

inputs $rould be required, since they appeared to perform
best under more idear growing conditions. The semi_dwarfs
were not as able to handfe stresses åmposed by weed cornpeti_
tion, Ìow ferti_líty or drought. Although no fertilizer by
genotype interactiong occwred for yield or its major compo_
nents, trends indicated that the short-statured naterial had
a greater requírenent for at l_east the first increment <strong>of</strong>
nitrogen relative to the tal1 genotypes. At the hígher
nitrogen levels this extra response did not continue.
fhe two semi-dwarfs whÍch performed best in this trial,
C7o3o32 and Minn64-62, galned their yield primarily frorn
production <strong>of</strong> more heads per unit area than the tatls. lfhey
had fewer kernels per head and lower kernel weight at most
sltes. Inereased N díd al"leviate some <strong>of</strong> these d.ifferentials
when growing conditions were adequate ¡ however. kernel weight
$ras least favourable at the hÍghest yield 1evels.
0n the average, Minn6&_ó2 was the highest yieldång
genotJæe. ¡iowever, its drawback was its lateness, since,
except under good growing conditions, it was unabre to conplete
its growing cyc1e, resur,ting ín greatry <strong>reduced</strong> kernel
size "
When lodging oecurred, the semi_dwarfs exhibited
superior resistance, which continued as the fertility level
increased. The gap between the lociging levels <strong>of</strong> the tall
and short types increased with N level, particularly for
mírn64-62, which showed no increase ln degree <strong>of</strong>, lodging as
N inereased.
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