الفهرس 
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Abstract
The target of this study was examining the effect of different concentrations and frequencies of application of potassium silicate on some vegetative growth characteristics, leaf chemical composition, yield, berries colouration % and quality of the berries of Flame seedless grapevines grown under Luxor region conditions.
This experiment included the following ten treatments from various concentrations and frequencies of application of potassium silicate :
1- Control .
2- Spraying potassium silicate once (growth start) at 0.05% (0.5 gL-1).
3- Spraying potassium silicate twice (growth start and again just after berry setting) at 0.05% ( 0.5 gL-1).
4- Spraying potassium silicate thrice (growth start just after berry setting and at one month later) at 0.05% (0.5 gL-1).
5- Spraying potassium silicate once at 0.1 % (1.0 g L-1).
6- Spraying potassium silicate twice at 0.1 % (1.0 g L-1).
7- Spraying potassium silicate thrice at 0.1 % (1.0 g L-1).
8- Spraying potassium silicate once at 0.2 % (2.0 g L-1).
9- Spraying potassium silicate twice at 0.2 % (2.0 g L-1).
10- Spraying potassium silicate thrice at 0.2 % (2.0 g L-1).
Therefore, thus study involved ten treatments. Each treatment was replicated three times, one vine per beach. The total number of selected vines for achieving of this study was 30 uniform in vigour vines. Potassium silicate (25% Si +10 % K2O) was sprayed once at growth start when the mean lengths of main shoot reached at least (30cm) (mid of March), just after berry setting (2nd week of April) and at one month lated (2nd weekof May). Triton B as wetting agent was applied at 0.05% to silicon solutions before spray. Control vines were sprayed with tap water containing Triton B at 0.05%. Spraying was done till runoff (1-2 L vine solution according to the date of spraying).
The present experiment was set up in a randomized complete block design (RCBD) with three replicates each consisted from one Flame seedless grapevine.
During both seasons, the following measurements were recorded:
1- Vegetative growth aspects namely main shoot length(cm) and leaf area (cm)2.
2- Leaf chemical components namely chlorophylls a & b , total carotenodis ( mg/ g F.W.) , N, P, K, and Mg ( as %) and Zn, Fe, and Mn (as ppm)
3- Percentage of berry setting.
4- Yield expressed in number of clusters / vine and weight (kg.)
5- Weight (g.) , length and shoulder (cm) of cluster
6- Percentage of berries colouration.
7- Physical and chemical characteristics of the berries namely weight, longitudinal and equatorial of berry, T.S.S. %, reducing sugars %, total acidity % ( as g tartaric acid/ 00 ml juice) and total anthocyanins ( mg/ 100 g F.W.)
The nearly same obtained data during both seasons could be summarized under the following main items:
1- Main shoot length and leaf area:
Both were remarkably stimulated due to using K- silicate once, twice, or thrice at 0.05 to 0.2% over the control. The maximum values were recorded on the vines that treated with K- silicate thrice at 0.2%.
2- Leaf chemical components:
Chlorophylls a & b , total carotenoids , N, P, K, Mg, Zn, Fe and Mn were remarkably improved in response to treating the vines once, twice, or thrice with K- silicate at 0.05 to 0.2% over the control. They were maximized in the vines treated with K- silicate thrice at 0.2% and were minimized in the untreated vines.
3- Percentage of berry setting , yield and cluster aspects:
Subjecting the vines with K- silicate once, twice or thrice at 0.05 to 0.2% had an obvious promotion on the percentage of berry setting, yield and cluster aspects (weight, length and shoulder) relative to the control. Since no measurable promotion on the yield was detected among eth higher two concentrations (0.1 & 0.2%) and frequencies of applications (twice or thrice). The recommended treatment from economical point of view was the application of K- silicate twice at 0.1%. Number of clusters / vine was unaffected in the first season of study.
4- Quality of the berries:
The best results with regard to both physical and chemical characteristics of the berries from economical point of view were obtained due to treating the vines twice with K silicate at 0.1%.
CONCLUSION
Under the conditions of this experiment and the resembling conditions, it is advised to spray Flame seedless grapevines twice at growth start and again just after berry setting with K- silicate at 0.1 % for promoting yield and quality.