الفهرس 
INTRODUCTION
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Abstract
Two field experiments were carried out in the Desert Research Center (D.R.C.), Agricultural Experimental Station at EL-Kharga Oasis (30.53 longitude, 25.45 latitude and elevation 78.8 m), New Valley Governorate, during 2010 and 2011 seasons, to study the effect of three cultivars of maize (Giza 10, Giza 321 and Giza 324), potassium rates, (0, 36 and 72 kg K2O/ fed. ) and boron spraying levels (0, 226, 452 and 678 ppm) on some growth characteristics at 75 days after sowing as well as, yield and its components and some chemical composition.
The experiment was laid out in a split-split plot design with six replicates. Maize cultivars treatment was arranged in the main plots, boron foliar application was allocated in the sub plots and potassium treatment occupied the sub-sub plots.
The important results can be summarized as follows:
1- Effect of cultivars:
1-1- Growth characters:
The differences among the three tested maize cultivars in the plant leaves area, LAI, SLW, days to 50 % silking and SPAD-units in 2010 and 2011 growing seasons were significant. While, the differences were not significant between maize cultivars on days to 50 % tasseling in the both seasons. Giza 321 cultivar gave the higher values of these parameters but, the differences were not significant between Giza 321 and Giza 324 for plant leaves area, LAI and SLW in the both seasons. Concerning to days to 50 % silking, there was delayed to 61.78 days with Giza 324, followed by 61.53 days with 321, while earlier silking of 61.33 days was recorded with Giza 10 cultivar.
1-2- Yield and its components:
Statistical analysis revealed that plant height, ear height, ear length, ear diameter, number of rows/ ear, No. of grains/ ear, grains weight/ ear, 1000-grain weight, shelling %, grain yield and biological yield were significantly affected by maize cultivars in both seasons. On the other hand, maize cultivars did not significantly differ in number of ears/ plant in 2010 and 2011 seasons.
The highest values of these traits were recorded for cultivar Giza 321 followed by cultivar Giza 324 while the minimum values were recorded for cultivar Giza 10 in the both seasons. The differences were not significant between Giza 321 and Giza 324 for ear height, ear diameter and shelling % in the first and second seasons. Also, the differences were not significant between Giza 321 and Giza 324 for grain yield and biological yield in the first season only.
1-3- Chemical composition:
There were a significant differences among maize cultivars on protein and total carbohydrate percent in grains and Fe and B concentration in ear leaf in both seasons, but potassium percent affected significantly by maize cultivars in the first season only. Giza 321 gave significantly the highest values of protein, total carbohydrate and potassium percent in grains. On the other hand, Giza 10 gave the highest values of Fe and B concentration in ear leaf followed by Giza 324 and 321 cultivars in the first and second seasons. However, the differences were not significant between Giza 321 and Giza 324 for protein percent and B concentration in ear leaf in the first and second seasons, potassium percent in the first season.
2- Effect of boron foliar:
2-1-Growth characters:
Plant leaves area, LAI, SLW, days to 50 % silking and SPAD-units were significantly affected by increasing levels of boron foliar from zero to 678 ppm in 2010 and 2011 growing seasons. On the contrary, No. of days to 50 % tasseling don’t affected significantly by increasing levels of boron foliar from zero to 678 ppm in both seasons. The highest values of plant leaves area, LAI and SPAD-units were obtained by applying 452 ppm B during 2010 and 2011 seasons. The highest values of SLW, No. of days to 50 % tasseling and silking were obtained by using 678 ppm B foliar application in the first and second seasons. The differences were not significant between 452 ppm and 678 ppm B foliar concerning to SLW and No. of days to 50 % silking in the both seasons.
2-2- Yield and its components:
Applying boron spray levels from zero to 678 ppm to maize under EL-Kharga Oasis conditions caused an increase in ear length, ear diameter, number of rows/ ear, No. of grains /ear, grains weight/ ear, 1000-grain weight, shelling %, grain yield and biological yield. This was true and significant in the first and second seasons. The plant height, number of ears/ plant and ear height was not significantly affected by boron foliar application in both seasons. Maximum values of these parameters were produced by 452 ppm B foliar in both seasons as compared with nil B in the second season. However, the differences between boron foliar application by 452 and 678 ppm were insignificant effect on ear length and biological yield in the first season only. but ear diameter, number of rows/ ear, 1000-grain weight and shelling % in both seasons.
2-3- Chemical composition:
Raising boron levels from 0 to 678 ppm had a significant effects on protein, total carbohydrate and potassium percents in grains. On the contrary, Fe and B concentrations in ear leaf reached to the highest concentration with control treatment (without B foliar) and decreased gradually with increasing spraying level in 2010 and 2011 growing seasons. Nevertheless, Fe concentration in ear leaf don’t affect significantly by levels of boron foliar in both seasons. Maximum values of all studied chemical composition were produced by using 678 ppm boron level ppm in compare to nil boron treatment in the both seasons, except, Fe and B concentrations in ear leaf as mentioned previous. The difference between the rates of 452 and 678 ppm B were not significant for protein and total carbohydrate percents in grains in both seasons. Further, in regard to potassium percent the differences among spraying of B levels 0, 226 and 452, 678 ppm didn’t reach to significant level in the two seasons.
3- Effect of potassium fertilizer:
3-1- Growth characters:
Potassium fertilizer application was significantly affected on plant leaves area, LAI, SLW, days to 50 % tasseling, days to 50 % silking and SPAD-units in both seasons. Raising the rate of K2O from 0 to 72 kg K2O/ fed. increased significantly all studied growth traits comparison by control (without K2O) in both seasons.
3-2- Yield and its components:
Increasing potassium fertilization rates 0 to 72 kg K2O/fed. caused a significant increase in all yield and its components of maize plants in the both seasons, except number of ears/ plant in the second season. The highest values of plant height, number of ears/ plant, ear height, ear length, ear diameter, number of rows/ ear, No. of grains /ear, grains weight/ ear, 1000-grain weight, shelling %, grain yield and biological yield were obtained at 72 kg K2O/fed. compared with control treatment (without any fertilizer). This is fairly true in both seasons.
3-3- Chemical composition:
Application of potassium fertilizer to maize plants was significantly increased protein, total carbohydrate and potassium percents in grains at the two growing seasons. The highest values of these chemical composition of maize plants were obtained by 72 kg K2O/fed. in both seasons comparing to the control treatment (unfertilized). Concerning to Fe and B concentrations of ear leaf, increasing potassium fertilization rates from 0 to 72 kg K2O/fed. caused a significant decrease Fe and B concentrations of ear leaf in the two seasons, since control treatment (without potassium fertilizer) gave the highest Fe and B concentrations of ear leaf
4- Effect of the interaction.
4-1- Growth characters:
4-1-1- Effect of the interaction between cultivars x boron foliar
The interaction between cultivars and boron foliar had a significant effect on plant leaves area, leaf area index, specific leaf weight and total chlorophyll (SPAD) in two seasons. On the other hand, the interaction between cultivars and boron foliar had insignificant effect on days to tasseling and days to silking in the both seasons. Moreover, Generally, Giza 321 plants cultivar sprayed with boron at 452 ppm was the best treatment compared with all treatments for all studied traits of growth characters in the two tested seasons. The lowest values of maize plants were recorded with Giza 10 cultivars under control (without boron treatment).
4-1-2- Effect of the interaction between cultivars x potassium
The interaction between cultivars of maize and potassium fertilizer rates was significantly affected on plant leaves area, leaf area index, specific leaf weight, days to 50 % tasseling and days to 50 % silking in the both seasons except, SPAD values in the second season only was not significant. The addition of 72 kg K2O/fed. along with the Giza 321 cultivar recorded the highest values of all studied traits of growth characters in both seasons. On the other hand, the lowest values for all growth characters were recorded by Giza 10 cultivar with control treatment (without potassium fertilizer) in both seasons.
4 -1-3- Effect of the interaction between boron foliar x potassium
The interaction between boron spraying treatments and potassium rates was significant on all growth criteria of maize plants except, specific leaf weight in the second season and days to tasseling in both seasons which don’t reached to the significant degree. The maximum values were obtained by spraying maize plants by 452 ppm boron with adding 72 kg K2O/fed. for all growth criteria of maize plants. On the contrary, the minimum values of these parameters were produced by control of the two treatments in the two seasons.
4-1-4- Effect of the second order interaction
The interaction among cultivars with boron spraying and potassium fertilizer rates had a significant effect on plant leaves area, leaf area index, specific leaf weight and days to 50 % silking in both seasons. The interaction between these studied factors was not significant effect on days to tasseling and total chlorophyll (SPAD) in the both seasons. Giza 321 cultivar spraying by 452 ppm and 72 kg K2O/fed. fertilizer gave the highest value of the studied growth traits in both seasons compared with all treatments. The lowest values of maize plants were recorded with Giza 10 cultivar under controls for boron foliar and potassium fertilizer (without boron and potassium treatments) in both seasons.
4-2- Yield and its components:
4-2-1- Effect of the interaction between cultivars x boron foliar
The interaction between maize cultivars and boron spraying was significantly affected on ear length, No. of grains/ ear, grains weight/ ear, 1000-grain weight and yields of biological and grain in both seasons. On the other hand, the effect of this interaction was not significant on some yield components i.e. plant height, No. of ears/ plant, No. of rows/ ear and ear height in the first and second seasons. Moreover, this interaction was affected significantly in the first season only on ear diameter, but in the second season was not significant. Also, the interaction effect among maize cultivars and boron spraying on shelling percent was significant in the second season, but in the first season was insignificant. Maximum values of the interaction between maize cultivars and boron spraying on yield and its components was obtained from plants attributed to Giza 321 cultivar and received 452 ppm as boron foliar application in the two seasons. The minimum values were obtained by Giza 10 cultivar under the control treatment of boron (without boron foliar) in both season.
4-2-2- Effect of the interaction between cultivars x potassium
All precedent traits of yield and its components were affected significantly by the interaction between maize cultivars and rates of potassium fertilizer in both seasons except, No. of ears/ plant and No. of rows/ ear don’t reach to significant level in the two seasons. Also, effect of this interaction on ear diameter was significant in the first season only. The highest values of yield and its components of maize plants were obtained by Giza 321 cultivar with the highest rates of potassium fertilizer (72 kg K2O/fed.) in both seasons. In this respect, the lowest values were achieved by the combinations of Giza 10 cultivar with control (without potassium) in the two seasons.
4-2-3- Effect of the interaction between boron x potassium
Plant height, ear length, No. of grains/ ear, grains weight/ ear, 1000-grain weight and yields of grain and biological were significantly affected by the interaction between boron foliar application and potassium fertilizer. While, No. of ears/ plant and ear diameter don’t affected significantly by the interaction in both season. On the other side, effect of the interaction between boron foliar application and potassium fertilizer was significant in the first season only. Concerning No. of rows/ ear and shelling %, but effect of this interaction was significant on the second season only concerning of ear height. The maximum increments for yield and its components were obtained by spraying maize plants by 452 ppm boron with adding the high rate of potassium fertilizer (72 kg K2O/fed.) in both seasons. In this respect, the lowest values were achieved by the control treatments for the two factors (boron and potassium) in the two seasons.
4-2-4- Effect of the second order interaction
A significant increases in plant height, ear length, No. of grains/ ear, grains weight/ ear, 1000-grain weight, shelling %, grain yield and biological yield during 2010 and 2011 seasons were detected. However, no significant effects were achieved for No. of ears/ plant, ear height, ear diameter and No. of rows/ ear in both seasons.
The maximum increase due to interactions among the three studied factors were obtained by cultivating Giza 321 maize cultivar spraying with 452 ppm boron and fertilization with 72 kg K2O/fed. in both seasons. Giza 321 cultivar surpassed Giza 324 and Giza 10 under spraying by 452 ppm boron at the high rate of potassium fertilizer.
4-3- quality characters:
4-3-1- Effect of the interaction between cultivars x boron foliar
Percentages of protein and total carbohydrates in grains and boron concentration of ear leaf for maize plants were significantly affected by the interaction between cultivars and boron foliar during both growing seasons. While, potassium percentage in grains and Fe concentration in ear leaf were none significance affected by this kind of the interaction in the first and second seasons. The highest values of these parameters were obtained by using Giza 321 maize cultivar with spraying plants by the high level of boron 678 ppm in the two seasons. Otherwise, Giza 10 cultivar with control treatment of B (without boron foliar) gave the minimum values of all chemical composition in the two growing seasons.
4 -3-2- Effect of the interaction between cultivars x potassium
Chemical composition of maize plants, percentages of protein and total carbohydrates in grains and Fe concentration in ear leaf were significantly affected by the interactions among maize cultivars and potassium fertilizer in the both seasons. Otherwise, potassium percentage in grains and boron concentration of ear leaf were not significantly affected by the interaction in the first and second seasons. Giza 321 cultivar under the highest level of potassium (72 kg K2O/fed.) gave the highest values of protein %, total carbohydrates % in grains and Fe concentration in ear leaf in the two growing seasons. The lowest values were obtained by Giza 10 with control treatment of potassium (without potassium fertilizer) during 2010 and 2011 seasons.
4-3-3- Effect of the interaction between boron x potassium
Significant increases in percentages of protein, total carbohydrates and potassium in grains and Fe concentration in ear leaf and boron concentration of ear leaf for maize plants in the first and second seasons were detected by the interaction between boron and potassium, but no significant effects were achieved on total carbohydrates % in the second season only due to application of such treatments. Moreover, generally, plants that sprayed with boron at 678 ppm boron and fertilized by 72 kg K2O/fed. were the best treatment compared with all treatments for all studied traits of chemical composition of maize in the two tested seasons. The lowest values were recorded with control treatments of B and K2O (without boron foliar and potassium fertilizer) in the two seasons.
4-3-4- Effect of the second order interaction
Chemical composition of maize plants percentages of protein and total carbohydrates in grains and Fe concentration in ear leaf for maize plants were markedly influenced by the interactions among maize cultivars with boron spraying and potassium fertilizer treatments during both growing seasons. Potassium percentage in grains and boron concentration in ear leaf were none significance affected by this kind of the interaction in the first and second seasons. The maximum values for these composition were obtained by Giza 321 cultivar with spraying by 678 ppm of boron and fertilization of potassium by the rate of 72 kg K2O/fed. in both seasons. The minimum values were recorded with Giza 10 under control treatments of B and K2O (without boron foliar and potassium fertilizer) in 2010 and 2011 seasons.