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

number <strong>of</strong> spíkes as nÍtrogen inereased. Schreiber and
Stanberry (f9Ø) indicated that nitrogen applied at <strong>plant</strong>ing
gave increased kernels per spike and kernel weight but
lowered the number <strong>of</strong> spikes per <strong>plant</strong>. This was probably
<strong>of</strong>fset by increasing the number <strong>of</strong> <strong>plant</strong>s and thereby
effectively giving more spikes per unit area, Gardener and
Rathjen (19?5) reported that variation in cultivar yieLds
with n5.trogen was due to r¡ariation in ear nwnbers, whíle
grain weight per ear reriained constant, since changes in
kernels per spike and kernel weight were <strong>of</strong> opposite magni-
tudes and compensated for each other. They indicated that,
in general, kernels per spike íncreased and kernel weight
dropped as nitrogen l"ncreased. Reisenauer and Díckson (1961)
also reported. a lower welght per kernel as nitrogen l-evel
increased .
Konishl (19?6) reported that fertÍtization resul,ted j.n
an increaged nu¡rber <strong>of</strong> spikes for all genotlrpe s I but at the
higher leve1s <strong>of</strong> fertíl"izer, genotypes responded differently"
l{e also reported that the re sponse <strong>of</strong> grain weight per spike
to fertilisation was varíab1e wlth some genotypes responding
positively and others negatívely.
Konishi's final conclusion regardlng the highe:' yielding
dwarf mutants was; 'rthe increased grain yield <strong>of</strong> dwarf
mutants by heavy fertilizer appLication ís principally due
to the increase (or not d.ecrease) ln the grain weight per
spike, but not by the nurnber <strong>of</strong> spikesn (Konishi, L9?6),
Increasing nitrogen fertÍlizer applieatíon has generally
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