In two field experiments conducted in 1991 and 1992 at Akure, Nigeria,
0–12 and 0–24 ml/l of the
plant growth regulator, paclobutrazol, and 0, 75 and 150 kg N/ha were
applied to maize in factorial
combinations. Substantial vegetative growth occurred with increasing N rates
in 1991 and this
accelerated 50% silking date. Paclobutrazol influenced maize growth at this
stage only in 1992 when
12 and 24 ml/l depressed plant height and increased both stem girth
and leaf number/plant.
Higher paclobutrazol application rates decreased plant height at maturity
in both years while, in
1991, 150 kg N/ha enhanced it, and also stem girth and shoot dry matter
yield. In 1991, both ear and grain dry weight yield/m2
increased with higher N rates while in 1992 4–24 ml/l paclobutrazol
enhanced ear dry yield/m2 compared with untreated maize.
Both chlorophyll a and b in the ear leaf increased with
higher rates of paclobutrazol and N
fertilizer, except in 1992 when high leaf N tended to mask the effect
of paclobutrazol. N fertilizer in
1991 enhanced the contents of N and Ca in the ear leaf while depressing
P, compared with untreated maize.