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Abstract
Two field experiments were carried out at the Experimental Research Center, Faculty of Agriculture, Moshtohor, Benha University, Kalubia, Egypt during the two successive summer seasons of 2005 and 2006. The aim of this work was to study the effect of four nitrogen levels, i.e., 60, 90, 120 and 150 kg N/ feddan on the productivity of nine maize genotypes. These genotypes included eight single crosses. Six of them were newly maize hybrids developed in the maize breeding program at the faculty of agriculture, Moshtohor. The other two hybrids were S.C. 10 and Pioneer 30k8. The last genotype was three way cross 310. Also, studying correlation and factor analysis was of the scope of this work. The experimental design was split plot design with four replications in both growing seasons. The four nitrogen levels were assigned in the main plot where maize genotypes were randomly distributed in the sup plots. Data recorded on date of silking,, plant height, ear height, ear length, ear diameter, number of rows/ ear, number of kernels/ row, 100 kernel weight, shelling percentage, ear weight, and grain yield/ feddan. Data were analyzed separately for each season and then combined analysis was performed over both seasons. Simple correlation coefficient was estimated. Factor analysis was also used in this study.
The obtained results could be summarized as follows:
Part I: Effect of N levels on maize genotypes:
a- Effect of N levels:
- Results indicated that Application of N significantly induced earliness regarding silking by 0.78, 0.97, and 2.0 days in the combined average compare with the lowest N level (60 kg / fed).
- The results showed that N application had a significant effect on plant and ear heights. Increasing N level from 60 to 90, 120 and 150 kg N/Fed, significantly increased maize plant height by 1.1, 3.4 and 5.0% respectively. The corresponding values for ear height were 3.0 , 4.8 and 5.4%, respectively compared with lowest treatment in the combined analysis.
- Increasing N level from 60 to 90, 120 and 150 kg N/Fed. significantly increased ear length by 3.6, 5.1 and 5.8%; ear diameter by 5.3, 6.2 and 7.7%; number of rows/ ear by 3.5, 7.1 and 7.8; number of kernels/ row by 4.1, 6.9 and 7.8%; 100 kernel weight by 3.1, 6.2 and 6.6%; shelling percentage by 1.2, 0.6 and 2.4 %; ear weight by 6.8, 9.4 and 9.7%; and grain yield/ feddan by 11.6, 17.6 and 19.9% over the lowest N level for the respective N levels in the combined data.
b- Genotype performances:
- The tested hybrids significantly varied in all studied traits in the combined analysis. For silking date the genotypes G1 and G3 were the earliest among the studied hybrids in the combined average recording 56.3 and 56.5 days from planting.
- The tested genotype G7 gave the highest values for both plant height and ear height recording 324.8 and 165.3 cm, respectively in the combined analysis of both growing seasons .
- Genotypes G3 and G6 were the best among studied hybrids since they produced the highest desirable values for ear length (20.8 and 21.1 cm); ear diameter (5.2 and 5.0 cm), number of rows/ ear (15.84 and 15.4), number of kernels/ row (47.0 and 45.6), 100 kernel weight (35.9 and 35.1 g), grain weight (295.7 and 285.1 g), and grain yield/ fed. (4555.2 and 4190.8 kg/ fed.), respectively, in the combined analysis.
- For shelling percentage, genotypes G3 and G4 gave the highest mean value being 84.5 and 83.6%, respectively, in the combined analysis.
c. Interaction effects:
- The interaction between N levels X genotypes significantly affected silking date where 60 or 90 kg N with genotype of maize No. 7 produced the highest value 64.3 & 62.8 days, respectively. The lowest value (55.6 days) was recorded by combining 60 kg N/fed. and genotype G1.
- Combining 120 kg N/ feddan with genotype 7 produced the highest values for plant and ear heights being 329.1 and 176.1 cm, respectively in the combined data.
- For ear length, combining 90 kg N/ feddan with genotype G3 produced the highest interaction (22.0 cm) in the combined data .
- The highest N level X genotype interaction for ear diameter was obtained with combining each nitrogen level with G3 recording the highest value for 120 kg N/ fed. with (4.3 cm).
- For number of rows/ ear, the most desirable interaction was detected by the application of 90 kg N/ feddan with genotype G2.
- The maximum number of kernels/ row was obtained by the interaction of 120 kg N/ feddan and genotype 7 in the combined analysis.
- For 100- kernel weight, the highest value was 38.88 which was recorded by combining 150 kg N level and genotype G6.
- Application of 150 kg N level with genotype 3 had the highest value for shelling percentage and ear weight being 86.1% and 322.5gm, respectively, in the combined analysis.
- For grain yield/ feddan, the maximum grain yield was 5161.5 kg in the combined data which was recorded by combining 150 kg N/ fed level and tested cross G3 of maize and the lowest value was 2673 .4 kg which was recorded by 60 kg N level and cross 9 .
- In conclusion, maize genotypes G3 and G6 seemed to be the most promising hybrids and could be used in the future maize production particularly with the high nitrogen levels.
Part II: Correlation and Factor Analysis:
a- Correlation Studies:
- Correlation coefficients between grain yield/ fed. and silking date was significantly negative (-0.427**), while it was significantly positive between grain yield/ feddan and each of ear diameter (0.552**), No. of rows/ ear (0.433*), No. of kernels/ row (0.670**), 100- kernel weight (0.445**) and shelling percentage (0.324*). The association between silking date and each of plant height (0.301*) and ear height (0.279*) was significant and positive, while it was significantly negative between silking date and each of No. of rows/ ear (-0.258*), No. of kernels/ row (-0.317*) and shelling percentage (-0.427*). There were significant and positive correlation values between plant height and each of ear height and ear length being 0.784** and 0.387*, respectively while it was significantly negative between plant height and shelling percentage (-0.312*). The correlation values between ear height and ear length was significantly positive, whereas it was significantly negative with No. of rows/ ear and shelling %. Ear length and ear diameter expressed significantly positive r values with each of No. of rows/ ear, No. of kernels/ row, 100- kernel weight and shelling percentage. Significant and positive correlation values were detected between No. of rows/ ear and each of No. of kernels/ row (0.243*), 100 kernel weight (0.467**) and shelling % (0.434**). Also, there were significant and positive r values between No. of kernels/ row and each of 100 kernel weight (0.440**) and shelling percentage (0.330*). Shelling percentage was significantly and positively correlated with 100 kernel weight (0.500*).
b- Factor Analysis:
- The factor analysis technique divided the studied variables into two main factors. These two factors accounted for 72.53 % of the total variability in the dependence structure of maize grain yield.
- The first factor included six variables and accounted for 46.44 %. These variables were plant height (20.50%), ear height (19.99%), ear length (17.10%), number of rows/ ear (13.56 %), number of kernels/ row (14.96 %) and 100 kernel weight (13.89 %). It is clear that these variables had a high loading coefficients and participate much more on the dependence structure. Most of these variables exhibited significant and positive correlation values with grain yield as previously mentioned.
- The second factor consists of three variables and accounted for 26.09 of the total variability of maize grain yield. These three variables were silking date (12.36 %), ear diameter (43.15 %) and shelling percentage (44.49 %).
- It could be concluded that selection for grain yield as well as its important components in addition to silking date, plant height and ear height would lead to maximizing total maize grain yield.