Abstract
The effects of production technology on seed quality of
wheat were studied through five sets of experiments
incorporating 1) time of planting and seed rate; 2) time of
planting and variety; 3) NPK fertilization; 4) irrigation and
seed rate; and 5) nitrogen rates and their split application.
Data relating to four categories of traits namely, a) seed
quality attributes, b) growth durations, c) vigour aspects
and d) yield and yield contributing characters were collected
and analysed from all the experiments.
In experiment with time of planting and seed rate,
progressive delay in sowing resulted in progressive increase
of seed protein content(%) and seed vigour measured in terms
of shoot elongation, root elongation and field emergence. But
the 1000-seed weight showed a gradual reduction with the
delay in sowing as a result of curtailment of seed filling
duration. The incidence of black point disease also got
reduced significantly and progressively due to delay in
sowing. Accumulation of growing degree days up to 31 December
showed significant effect on yield, yield contributing and
seed quality characters. The biological, seed and protein
yields did not show significant variation due to seed rates
from 80 to 240kg/ha. At higher seed rates, the advancement of
higher ears/m² was compensated adequately by the production
of additional seeds/ear at lower seed rates to equalise
yield. The 1000-seed weight had strong negative associations with shoot elongation (r=-0.81***), root elongation (r=-
0.63***) and field emergence both from 5 cm and 10 cm depth,
but had positive relationship with seed yield (r=0.87***).
In experiment with time of sowing and variety, the
varietal requirements of GDD (>4.4°c) for completion of preanthesis phenophase were more variable, while those for
post-anthesis period varied marginally. Variability in postanthesis day durations amongst varieties was due to
temperature variations initiated by pre-anthesis
differential heat requirement of varieties. On the basis of
GDD, and planting date dependent anthesis date, seed growth
period, yield, yield contributing and seed quality characters
can be assessed with more accuracy than the day duration for
specific varieties. Varieties requiring shorter heat units
for completion of pre-anthesis phenophase may be suitable for
short growing season as in Bangladesh. Across varieties, a
compensating tendency of yield contributing characters was
observed. A variety with higher 1000-seed weight was found to
be accompanied by lesser seeds/m² and vice-versa. Higher
yield in a variety was accompanied by lower protein
content (%).
In experiment with NPK fertilization, increase in
nitrogen rates decreased 1000-seed and hectolitre weights
but increased biological and protein yields. Although seed
yield with 100kg/ha N was identical with that of 140 kg/ha N,
the harvest index was higher with the former. Phosphosus application significantly increased both shoot and root
elongation. Potassium application increased 1000-seed and
hectolitre weights. Nitrogen rate at 140 kg/ha with 80 kg/ha
P205 maximised root elongation. Lower N(60kg/ha) with lower
P205 (40kg/ha) and higher N (140kg/ha) with higher
P205 (80kg/ha) interacted favourably to give higher field
emergence. Eighty kg/ha P205 with 40kg/ha K20 interacted to
produce highest root mass.
In experiment with irrigation and seed rate, the zero
irrigation produced highest 1000-seed and hectolitre weights
but not higher yields because of limited sink size. The root
elongation showed no variation at zero irrigation while the
weight was higher than that of all other treatments. Field
emergence from 5 cm depth increased with increased irrigation
frequencies. The effects of seed rate on different
characters in this experiment were similar with those of time
of sowing and seed rate experiment, except the 1000-seed
weight. The field emergence from 5 cm depth was highest at
160kg/ha seed rate. With higher HI, lowest seed rate (8о
kg/ha) gave significantly higher yield than that of higher
seed rate (140 kg/ha). Seed rate of 80 kg/ha with four
irrigations produced highest number of seeds/ear. The 1000-
seed weight was negatively correlated with the seed yield
(r=-0.68***) and the seed yield had in turn negative
association with root weight (r=-0.40*).
In experiment with nitrogen rates and their split
application, 140kg/ha N produced higher sink size as contributed by higher seeds/ear and ears/m² but decreased
1000-seed weight. The black point disease decreased at
100kg/ha N. Increased N application increased root
elongation. Seeds produced from lower nitrogen rate showed
significantly higher emergence. Three split application of
nitrogen gave the highest 1000-seed and hectolitre weights.
Two splits of 140kg/ha N rate gave the highest percentage of
germination, protein content and protein yield without
affecting the seed quality in terms of vigour. The adverse
effect of higher nitrogen rate could be minimized bу
increasing the split application. The field emergence both
from 5 cm and 10 cm depth and the 1000-seed weight was the
highest at three split application of nitrogen. In 60 kg/ha N
rate, single, and in 140kg/ha N rate three split applications
tended to give insignificantly higher yields in comparison to
other splits. Thousand seed weight showed negative
correlation with yield(r= -0.67*) and positive correlation
with field emergence at 5 cm (r= 0.93**) and 10 cm (r= 0.66*)
depths.
On the whole, seed size was found to have been enhanced
by early planting, higher P and K but lower N application,
three N splits and no irrigation. It had varietal difference.
The protein content evidently increased but the seed size
decreased with delay in sowing from 5 November. Similarly,
addition of N fertilizer increased seed protein content but
reduced seed size. Small sized high proteinous seeds of late
planting origin showed higher vigour. Planting between 5 to
15 December gave more biological seed units and emergeable
seeds/m² enabling their rapid numerical multiplication. Seed
sowing by emergeable count might be an improvement over
quantitative seeding practice.