الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 156 |  |  |
| | | from | 156 | | |
Abstract
The aim of this study was to investigate the influence of planting date and
nitrogen fertilizer levels on growth and yield of two maize varieties, namely, Giza 2
and Three Way Cross 310 (T.W.C. 310) ..The techniques utilized included multiple
linear regression, fitting polynomial and segmented curves, and economic analysis
of the response curves. The work in this study was divided into two parts, Agronomic
aspects and Statistical aspects.
Firstly: Agronomic aspects:
Two years of field experiments were conducted at the Research and
Experimental Center of the Faculty of Agriculture at Moshtohor, Egypt, in 1991 and
1992 seasons. The experimental treatments were as follows:
1- Three planting dates, i.e, early (May 1st), intermediate (June 1st) and late (July
1st).
2- Two maize varieties, namely, Giza 2 and T.W.C. 310.
3- Five nitrogen fertilizer levels (30,60,90, 120 and 150 kg Nlfad).
The design used was strip plot design with three replicates in the first season
and four in the second one for each planting date. Varieties were in the vertical
strips and nitrogen fertilizer levels in the horizontal strips. Combined analysis over
both years was made for the three planting dates of single experiments for each
season separately.
The characters studied were number of leaves/plant, leaf area of the topmost
ear (ern’), leaf area index, plant height (em), ear height (em), stem diameter (mm),
ear length (em), ear diameter (mm), number of rows/ear, number of kernels/row,
grain yieldlfaddan (kg) grain yield/plant (gm), shelling percentage (%), weight of 100
kernels (gm).
Secondly; Statistical aspects;
Three response models, namely, linear plus plateau, quadratic and quadratic
plus plateau were fitted to the yield data of the two tested varieties in the the three
planting dates during 1991 and 1992 seasons. Comparisons among those models
were based on the mean square error (MSE). The model which had the least mean
square error was considered to be the best model fitted to the yield data.
The price of nitrogen used in the present study, and the price of maize grains
considered for the economic analysis were prevailing in Cairo, Egypt during 1993,
l.e. £.E 1.2238/kg for nitrogen and £.E O.54/kgfor maize grains.
The regression analysis using a stepwise procedure was applied to the data
over both seasons including the plant characteristics mentioned before over all
three dates of planting over both Giza 2 and T.W.C. 310 varieties, and over the five
levels of nitrogen fertilizer used in this study.
The results obtained could be summarized as follows:
Agronomic aspects:
a- Effect of planting dates:
1- Delaying planting from May to June and July significantly reduced number of
leaves/plant by 10.00% and 15.48%, respectively in the 1991 season. The
I
corresponding reductions were 7.45°”-and 12.96% in the 1992 season in the same
respective planting dates. .
2- Leaf area of the topmost ear was markedly reduced as a result of delaying
planting date from May to June and July. The reduction reached 15.79% and
23.75% in the 1991 season, being 5.48% and 23.36% in the 1992 season.
3- A significant reduction in L.A.I of 23.77% and 33.79% in the 1991 season and of
16.93% and 26.80% in the 1992, resulted from delaying maize planting from May to
June and July, respectively.
4- Planting dates significantly affeded plant height. Reductions in maize plant
height of 8.12% and 24.92% in the 1991 season, and of 7.33% and 13.43% in the)
1992 season, were recorded due to delaying planting from May to June and July,
respectively.
5- Delaying maize planting from May to June and July reduced significantly ear
height by 3.59% and 20.43% in the 1991 season, being 8.99% and 15.46% in the
1992 season, respectively.
6- A significant reduction in stem diameter of 17.98% and 23.84% in the 1991
season and of 4.04% and 5.87% in the 1992 season resulted from delaying maize
planting from May to June and July, respectively.
7- Delaying planting from May to June reduced significantly ear length, ear
diameter, number of rows/ear and number of kernels/row by 8.07%,7.83%,
3.00% and 16.91%, respectively in the 1991 season, being 5.31%,4.06%,4.77%
and 9.37% in the 1992 season. Further delaying of planting from May to July
reduced significantly the four previous ear characters by 14.51%, 9.89%, 4.53% and
30.17%, respectively in the 1991 season, and by 23.46%, 7.04%, 8.38% and
27.22% in the 1992 season.
8- In May planting, grain yield/plant, shelling percentage and grain index
outweighed those of June planting by 42.61%, 5.92% and 7.56% in the 1991
season, respectively and 40.29%, 2.55% and 3.22% in the 1992 season,
respectively. Furthermore, these three traits recorded increase in May planting by
66.65%, 14.96% and 9.60% compared with July planting in the 1991 season,
respectively. In the 1992 season, the increases from the May to July planting were
46.00%, 3.14°k and 18.59% for grain yield/plant, shelling percentage and grain
index, respectively.
9- Grain yielcllfad. was significantly affected by planting date in the 1991 season.
On the other hand, in the 1992 season the differences in the grain yield were not
sufficient to reach the a.05level of significance. However, May planting outyielded
June planting by 24.69% and 6.53% in the firstand second season, respectively
Morever, May planting outyielded July planting by 75.38% and 42.00% in the 1991
and 1992 season, respectively.
b- Effect of variety:
1- In the 1991 season, T.W.C. 310 significantly surpassed Giza 2 by 3.18%, 8.17%,
12.52%, 3.71%, 7.86% and 11.11% concerning number of leaves/plant, leaf area
of topmost ear, L.A.I, plant height, ear height and stem diameter, respectively.
In the 1992 season, T.W.C. 310 was significantly superior to Giza 2 by 5.50% in
number of leaves/plant, 10.43% in leaf area of topmost ear, 16.04% in L.A.I, 3.39%
in plant height, 10.41% in ear height and 12.01% in stem diameter.
2- Ear length of T.W.C. 310 was significantly higher than that of Giza 2 by 12.06%
and 15.35 in the first and second season, respectively.
3- With regard to ear diameter, Giza 2 significantly surpassed TW.C. 310 by
4.16% in the 1991 season. In the 1992 season, Giza 2 also surpassed T.W.C. 310
by 1.07% but the difference was not significant.
4- Number of rows/ear of Giza 2 was significantly higher than that of T.W.C. 310 in
both seasons of the study. Giza 2 surpassed T.W.C. 310 by 9.57% and 9.00% in the
first and second season, respectively.
5- Concerning number of kernels/row, T.W.C. 310 surpassed significantly Giza 2
by 20.74% and 19.31% in 1991 and 1992 season, respectively.
6- Grain yieldlfad. of Giza 2 was slightly higher than that of T.W.C. 310 with
significant difference in the 1991 season, while T.W.C. 310 significantly outyielded
Giza 2 by 13.57% in the 1992 season.
7- T.W.C. 310 significantly surpassed Giza 2 in grain yield/plant by 10.36% in the
first season and 14.44% in the second season.
8- With regard to shelling percentage, no significant difference was detected
between the varieties in both seasons. Slight differences were found in favour of Giza 2 in the 1991 season, but of T.W.C. 310 in the 1992 season.
9- Weight of 100 kernels of T.W.C. 310 was higher than that of Giza 2 with a
significant difference of 5.73% in the 1992 season only.
c- Effect of nitrogen fertilizer level:
1- Number of leaves/plant was not significantly affected by nitrogen levels in both
seasons of the study.
2- Leaf area of the topmost ear increased significantly, in the 1992 only, by 4.13%,
9.24%, 4.60% and 9.17% with the increase in N level from 30 to 60, 90, 120 and
150 kg Nlfad, respectively. In the 1991 season, the increase in N level had no
significant effect on this character.
3- L.AJ was not significantly affected by the increase in N level in spite of a slight
increase in the 1992 season.
4- Plant height, ear height and stem diameter were not significantly affected by N
level in both seasons of experimentation.
5- Increasing the N level from 30 to 60, 90, 120 and 150 kg Nlfad increased ear
length by 3.72%, 1.13%, 1.24%, and 0.65%, respectively in the 1991 season
though without significant differences. On the other hand, in the 1992 season ear
length increased significantly by 5.70%, 8.57%, 9.40% and 11.69% as a result of
increasing N level from 30 to 60,90,120 and 150 kg Nlfad, respectively.
6- Ear diameter was significantly affected by N level in the 1991 season only. The
increase in ear diameter was 0.02%, 0.08%, 0.88% and (-2.40%) in the 1991
season, being 0.04%, 1.95%, 2.20% and 2.28% in the 1992 season as a result of
increasing N level from 30 to 60,90,120 and 150 kg Nlfad respectively.
7- Number of rows/ear showed no significant response to the increase in N level
in both seasons of the study.
8- Number of kernels/row increased significantly in the 1992 season by 4.05%,
( 122 )
10.03%, 9.97% and 13.32% when the N level increased from 30 to 60,90,120 and
150 kg Nlfad, respectively. On the other hand, this character did not increase
significantly in the 1991 season.
9- Grain yieldlfad. was significantly affected by N level in both seasons. In the 1991
season, increasing N level from 30 to 60, 90, 120 and 150 kg Nlfad increased grain
yield by 8.27%,22.55%, 11.70% and 16.58%, respectively. In the 1992 season, the
grain yield increased by 17.45%, 38.26%, 32.00% and 43.97%, respectively for the
same respective N levels.
10- Grain yield/plant was significantly ,affected by N level in the second season,
where raising the N level from 30 to 60, 90, 120 and 150 kg Nlfad markedly
increased grain yield/plant by 9.09%, 16.98%, 19.22% and 16.14%, respectively. In
the first season, the increase in N level failed to show any effect on this trait.
11- Neither shelling percentage nor grain index were significantly affected by N
level in both seasons of experimentation.
d- Interaction effects:
1-Interaction between planting date and varieties:
1- Number of leaves/plant was significantly affected by the interaction between
planting date and varieties in the 1992 season. The highest value of this trait was
14.25 recorded with T.W.C. 310 planted in May and lowest value was 11.86
recorded with Giza 2 planted in July.
2- Planting date X varieties interaction significantly affected plant height in the
1991 season. The maximum plant height of 309.00 emwas recorded with T.W.C.
310 planted in May and the shortest height was 229.33 em recorded with Giza 2 in
July planting.
3- With stem diameter the results showed that planting date X varieties interaction
significantly affected this trait in the 1992 season. The greatest stem diameter was
28.53 mm recorded with T.W.C. 310 under May planting and the smallest diameter
was 19.60 mmof Giza 2 planted in July.
4- number of kernels/row was significantly affected by the interaction between
planting date and varieties in both seasons. The greatest number of kernels/row was
recorded under the May planting with T.W.C. 310 being 46.71 and 43.34 in 1991
and 1992 seasons, respectively. The lowest number of kernels/row was produced by
Giza 2 under July planting being 28.39 and 27.11 in the first and second season,
respectively.
5- Planting date X varieties interaction had a significant effect on grain yield/plant
in the 1992 season. The highest value of grain yield/plant was 207.16 gm recorded
with T.W.C. 310 planted in May. The lowest value was 114.87 gm recorded with
Giza 2 planted in July.
6- Concerning grain yieldlfad., a significant interaction effect was recorded
between planting date and varieties in the 1991 season. The highest grain yield was
3091.94 kglfad which was obtained by Giza 2 under May planting and the lowest
grain yield was 1543.73 kglfad produced by T.W.C. 310 in July planting.
II-Interaction between planting date and N level:
1- The effect of the interaction between planting date and N level was significant on
leaf area of the topmost ear in the 1992 season. The highest leaf area was 764.20
em2 resulted from a May planting supplied with 90 kg Nlfad and the lowest area was
504.10 em2 recorded with the July planting supplied with 30 kg Nlfad.
2- Ear length was significantly affeded by planting date X N level interaction in both
seasons. The maximumvalues of ear length were 21.30 em in 1991 and 21.25 em in
1992 which were obtained from may planting supplied with 150 and 90 kg Nlfad in
the first and second season, respectively. The lowest ear length was 16.84 em in the
1991 season recorded with July planting and 90 kg Nlfad, whereas in the 1992
season the combination of July planting and 30 Kg N/fad produced the shortest ears
having 14.10 em length.
3- Planting date X N level interaction significantly affected ear diameter in the 1991
season. The greatest diameter was 52.25 mmresulted from May planting and 60 kg
Nlfad and the smallest diameter was 45.27 mmrecorded from the July planting and
30 kg N/fad.
4- A significant interaction effect of planting date and N level was detected on grain
yield/plant in the 1991 season. The highest grain yield/plant was 243.22 gm
obtained from the May planting with 30 kg Nlfad and the lowest yield was 132.59 gm
recorded with the July planting and 150 kg N/fad.
5- Weight of 100 kernels was significantly affected by the interaction between
planting date and N level in the 1991 season. The highest grain index was 38.03 gm
which was recorded with the May planting and 90 kg Nlfad and the lowest index was
32.37 gm obtained from the July planting with 30 kg N/fad.
6- The grain yieldlfad. was significantly affected by the interaction between
planting date and N level in both seasons of experimentation. The maximum grain
yield in the 1991 season was 3643.73 kglfad which was produced from the May
planting with 90 kg Nlfad level and the lowest yield was 1561.00 kglfad produced in
July and supplied with 150 kg Nlfad. In the 1992season, the May planting supplied
with 150 kg Nlfad produced the highest grain yield which was 1848.00 kg whereas
July planting with 60 kg Nlfad produced the lowest yield.
III-Interaction between varieties and N level:
1- A significant interaction effect of varieties and N level was detected on number of
leaves/plant in the 1992 season. The greatest number of leaves/plant was 13.53
recorded with T.W.C. 310 supplied with 60 kg Nlfad and the smallest number was
12.45 recorded with Giza 2 combined with 60 kg N1fad.
2- Varieties X N level interaction significantly affected maize plant height in the
1992 season.
The maximum plant height was 249.75 emobtained by T.W.C. 310 supplied with
120 kg Nlfad and the shortest plants were those of Giza 2 supplied with 120 kg
Nlfad which has a height of 232.83 em.
3- Stem diameter of maize plants was significantly affected by the interaction
between varieties and N level in the 1991 season. The greatest diameter was 25.02
mm recorded with T.W.C. 310 supplied with 30 kg Nlfad and the smallest diameter
was 21.56 mm recorded with Giza 2 plants supplied with 90 kg Nlfad.
4- Grain yield/fad. was significantly affected by the interaction between varieties
and N level in the 1992 season. The highest grain yield was 1878.30 kg which was
produced by T.W.C. 310 supplied with 150 kg Nlfad and the lowest yield was
1117.80 Kg produced by Giza 2 supplied with 30 kg Nlfad.
IV- Effect of the 3-way interaction:
1- Stem diameter was significantly affected by the interaction between planting
date, varieties and N level in the 1992 season. The greatest diameter was 24.90 mm
which was recorded with the combination of T.W.C. 310 planted in May and
supplied with 30 kg Nlfad.
2- Number of kernels/row was also significantly affected by the three way
interaction in the 1992 season. The number of kemelsJrowwas 47.50 recorded with
T.W.C. 310 planted in May and supplied with 150 kg Nlfad.
3- Planting date X varieties X N level interaction significantly affected grain
yieldlfad. in the 1992 season. The highest grain yield was 2149.00 kg which was
recorded with T.W.C. 310 planted in May and supplied with 150 kg Nlfad and the
lowest yield was 759.25 Kg obtained from Giza 2 planted in July and given 30 kg
N1fad.
Statistical aspects
a- Response curve analysis:
1- In the 1991 season, data of May planting showed that the best model fitted to the
yield data of variety Giza 2 was quadratic plus plateau model, whereas linear plus
plateau model fit well to the yield of T.W.C. 310 variety. In June and July plantings,
the best model was linear plus plateau for the two tested varieties.
2- In the 1992 season, the best model fitted to the yield data was linear plus plateau
model for the two varieties in May planting and also for Giza 2 variety in June
planting. The quadratic model fit well to the yield ofT.W.C. 310 variety in June
planting and also for both varieties in July planting.
b- Economic analysis:
1- In the 1991 season, the economic optimum nitrogen rate ranged from 0 to 110 kg
Nlfad for the two tested varieties in May, June and July plantings. Grain yield at
optimum N rate ranged from 1,795.00 to 3,330 kglfad. However, The net profit
ranged from 969.30 to 1691.73 £.Elfad.
2- In the 1992 season, the economic optimum N rate ranged from 60 to 150 kg Nlfad
for the two varieties in the three plantings. The grain yield at economic optimum N
rate ranged from 1,437.00 to 1,945 kglfad. However, the net profit ranged from
592.41 to 916.91 £Elfad.
e- Stepwise regression analysis:
1- The results indicated that 68.75% of the total variation in the yield could be
linearly related to the studied variables, 66.99% of the total yield variation could be
attributed to the variables included into the model and 1.76% could be due to the
eliminated variables.
2- The variables included to the model could be arranged, according to their relative
importance as measured by the partial R2, in a descending order as follows: years,
first planting date (May 1st), second planting date (June 1st), shelling percentage,
ear length, weight of 100 kernels, plant height, nitrogen fertilization and varieties.