Abstract
Series of field experiments were carried out in Rabi (winter)
season of 1987-88, 1988-89 and 1989-90 on the farm of Bangladesh
Agricultural Institute, Dhaka to evaluate the performance of one
rapeseed variety Sonali Sarisha (Brassica campestris L.) under 4 nitrogen
doses (0, 60, 120 and 180 kg/ha), 4 sulphur doses (0, 10, 20 and 30
kg/ha) and 4 population density levels (100, 400, 700 and 1000
thousand plants/ha). The experiment was laid out in a split-split
plot design, with nitrogen levels as in main plots, sulphur in sub
plots and population densities in sub-sub plots. The experiment had
three replications.
The farm has clay loam soil with N and S deficiencies. Under such
a nutrient status application of nutrients (N and S) significantly
improved all plant growth characters, yield attributes, seed and
stover yields, oil and protein contents, oil yield, N and S
contents and their uptake by the crop of Sonali Sarisha. The
treatments No and So recorded the lowest value with respect to all
the above characters except seed oil content for No level.
Among the four N levels tested, 120 kg N/ha was significantly
superior to all other N treatments in increasing plant height,
inflorescence length, DM accumulation in leaves, stems, flowering
branches and siliquae. Higher LAI, LAD, CGR, RGR values were
recorded at 120 kg N/ha. Number of primary branches, siliquae in
the main axis, per plant and/m², length of siliqua, seeds per
siliqua and 1000 seed weight showed significant response along with
higher seed and stover yields at 120 kg N/ha. However, oil content
in seed got reduced at 120 kg N/ha, while oil yield and protein
content increased. Sulphur content, nitrogen and sulphur uptake by
the crop also increased significantly at 120 kg N/ha.
Application of sulphur at 30 kg/ha significantly improved LAI, LAD
and DM accumulation in leaves, stems and siliquae. Applied sulphur
also increased number of siliquae/m², siliqua length, seeds per
siliqua and 1000 seed weight. Higher S dose (30 kg/ha)
significantly increased seed and stover yields, oil content and oil
yield except protein content. Higher N and S uptake by the crop
were recorded when sulphur was applied to the soil. At lower levels of population density(PD) there was a significant
increase in plant height and inflorescence length. At early growth
stages more DM accumulated in leaves, stems, flowering branches and
higher LAI, LAD, CGR values were observed at higher PD levels,
while at later stages the PD at 400,000 plants/ha showed better
influence on the above traits. Higher RGR values were also observed
at different stages of growth under the PD of 400,000 plants/ha.
Lower PD increased the number of primary branches, number of
siliquae in the main axis, number of siliquae per plant, length of
siliqua, seeds per siliqua and 1000 seed weight. However, these
differences had no significant effect on seed yield.
Maximum number of siliquae/m², higher seed and stover yields and
higher values of harvest index were registered under 400,000
plants/ha. Lower PD reduced oil and increased the protein content
in seed. However, higher oil yield per hectare was recorded at
400,000 plants/ha.
Higher concentration of N and S were observed in the crop at lower
PD, while more N and S accumulation, oil yield and uptake of N and
S were registered at a PD level of 400,000 plants/ha, because of
higher DM and seed yield/ha.
Maximum LAD and RGR values were recorded at 40 to 55 DAS, while
higher CGR values were observed at 55 to 70 DAS except in 1987-88
season irrespective of treatments. With the advancement of crop age
LAI decreased but NAR increased.
Under higher PD Sonali Sarisha flowered earlier by 4 days and
subsequently matured earlier by 7 to 8 days. PARI was more in 120
kg N, 30 kg S and 400,000 plants/ha. Higher mortality were recorded
at higher N and PD levels, however, higher S doses significantly
reduced the mortality rate.
Sulphur interacted with nitrogen for 50 per cent flowering,
siliquae setting, dry weight of leaves, stems, siliquae; LAI, LAD,
PARI, 1000 seed weight, seed and stover yield, oil and protein
contents, N and S contents and S uptake. Higher response was
observed with higher S level and N at 120 kg/ha in comparison to
other levels of N treatments.
Nitrogen and PD interacted with each other for plant height, dry
weight of leaves, stems, flowering branches, siliquae, TDM, LAI,
LAD, CGR, RGR, NAR, PARI, days to 50 per cent flowering, completion
of siliquae setting, maturity and mortality percentage,
inflorescence length, branch number per plant, siliquae in the main
axis, per plant and/m², length of siliqua, 1000 seed weight, seed
and stover yield, harvest index, oil and protein contents, N and S
contents and their uptake. In general, PD level at 400 thousand
plants along with 120 kg N/ha showed better performance for the
above traits in comparison to other combinations of treatments.
Interaction effect of S and PD showed higher plant height, dry
weight of leaves, stems, TDM; LAD, CGR, RGR, NAR, PARI, mortality
percentage, siliquae number in the main axis, per meter square,
length of siliqua, seed yield, oil and protein contents, N and s
contents and their uptake. Higher response of N and PD was observed
for the PD at 400,000 plants/ha in addition to 20 and 30 kg S/ha in
comparison to other combinations of treatments.
Higher order interaction of N, S and PD responded better with
respect to DM production of leaves, stems, TDM, RGR, PARI,
siliquae/plant, seed yield, oil and protein contents, N and S
contents and their uptake. Population density at 400,000 plants
along with 120 kg N and 30 kg S/ha gave higher results for the
above characters. The study suggests that PD level up to 400,000
plants, N and S levels up to 120 and 30 kg/ha can be increased for
beneficial effect on the yield of Sonali Sarisha cultivar. By using
Willcox's inverse yield-N-law the maximum yield/ha of Sonali
Sarisha was calculated (7.76 t/ha).