الفهرس 
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Abstract
This study was carried out during 2014 and 2015 seasons on sixty uniform in vigour 8- years old Superior grapevines. The selected vines are grown in a private vineyard located at Armant district Luxor Governorate where the texture of the soil is sandy. The selected vines are planted at 1.5 x3 meters apart. The chosen vines were pruned via cane pruning method leaving 72 eyes/ vine (six fruiting canes x 10 eyes plus six renewal spurs x two eyes) using Gable supporting method. Winter pruning was carried out at the first week of Jan. during both seasons. Drip irrigation system was followed.
This study was planned to examine the effect of different concentrations and frequencies of application of potassium silicate in growth, vine nutritional status, yield and quality of Superior grapes.
This experiment consisted from the following twenty treatments from two factors (A & B). The first factor (A) contained the following five concentrations of potassium silicate namely a1) 0.0, a2) 0.05, a3) 0.1, a) 0.2 and as) 0.4 % . The second factor (B) comprised from four frequencies of application of potassium silicate namely:
b1) Carrying out one spray at growth start (1st week of Mar.)
b2) Carrying out two sprays at growth start and again at three weeks later (4th week of Mar.)
b3) Carrying out carrying out three sprays at growth start, three weeks later and just after berry setting (2nd week of Apr.)
b4) Four sprays at growth start, three weeks later, just after berry setting and three weeks later (1st week of May).
Each treatment was replicated three times one vine per each. Triton B as a wetting agent was added to all solutions of potassium silicate at 0.05% and spraying was done till runoff. Randomized complete block design (RCBD) in split plot arrangement was adopted. The five concentrations and the four frequencies of potassium silicate application occupied the whole and subplots, respectively.
During both seasons, the following measurements were recorded:
1- Vegetative growth characteristics namely main shoot length(cm.), number of leaves/ shoot, leaf area, wood ripening coefficient, pruning wood weight / vine (kg.) and cane thickness (cm.)
2- Leaf pigments namely chlorophylls a, b, total chlorophylls and total carotenoids (mg/ 100 g F.W.)
3- Percentages of N, P, K and Mg and leaf content of Zn, Mn, Fe and Cu (as ppm)
4- Percentage of berry setting.
5- Yield expressed in weight (kg.) and number of clusters / vine.
6- Weight (g.), length and shoulder (cm.) of cluster.
7- Percentage of shot berries.
8- Physical and chemical characteristics of the berries namely weight (g.), longitudinal and equatorial (cm.) of berry, T.S.S. %, total acidity % ( as g tartaric acid/ 100 ml juice), T.S.S./ acid, reducing sugars as well as nitrate and nitrite in the juice (ppm).
The nearly same obtained data during both seasons could be summarized under the following main topics.
1- Vegetative growth characteristics :
Growth aspects namely main shoot length, number of leaves/ shoot. Leaf area, wood ripening coefficient, pruning wood weight and cane thickness were greatly stimulated in response to treating Superior grapevines, once, twice, thrice, or four times with potassium silicate at 0.05 to 0.4%. The promotion was materially associated with increasing -concentrations and frequencies of application of potassium silicate. No measurable promotion on these growth aspects were detected among the higher two concentrations (0.2 & 0.4%) and frequencies of application (thrice or four times). Carrying our four sprays of potassium silicate at 0.4% gave the maximum values.
2- Chemical constituents of leaves:
Carrying out one, two, three or four sprays of potassium silicate at 0.05 to 0.4% had an announced stimulation on chlorophylls a & b, total chlorophylls, total carotenoids, N, P, K, Mg, Zn, Fe and Mn in the leaves comparing to the check treatment. There was a gradual promotion on these chemical constituents with increasing concentrations and frequencies of application of potassium silicate. Meaningless stimulation was observed among the higher two concentrations and frequencies of potassium silicate application. The present treatments had no effect on the leaf content of Cu.
3- Percentage of berry setting, vield and cluster aspects:
Treating Superior grapevine with potassium silicate at 0.05 to 0.4 % once, twice; thrice or four times succeeded in improving the percentage of berry setting, yield, number of clusters, vine as well as cluster weight and dimensions (length & shoulder) over the check treatment. The promotion was in proportional to the increase in concentrations and frequencies of application. No material promotion on these traits was observed among 0.2 to 0.4% as well as between using three or four sprays ”of potassium silicate. Therefore, from economical point of view, it is suggested to use potassium silicate at 0.2% thrice for promoting berry setting %, yield and cluster weight.
4-Percentage of shot berries:
Such undesirable phenomenon greatly declined with using potassium silicate at 0.05 to 0.4%, once, twice, thrice, or four times over the control treatment. The reduction was greatly related to the increase in concentrations and frequencies of application without major reduction among the higher two concentrations and frequencies. Carrying out three sprays of potassium silicate at 0.2% gave the lowest values, from economical point of view.
5- Some physical and chemical characteristics of the berries
An obvious promotion was observed on physical and chemical characteristics of the berries in terms of increasing berry weight and dimensions (longitudinal and equatorial) T.S.S. %, T.S.S./ acid and reducing sugars % and decreasing total acidity and both nitrite and nitrate in the juice owing the using potassium silicate at 0.05 to 0.4 % once, twice, thrice or four times over with control treatment. The promotion was appreciably related to the increase in concentrations and frequencies of application. Increasing concentrations from 0.02 to 0.4% as well as frequencies of application from three to four times failed to show clear promotion on quality of the berries. The best results with regard to quality of the berries were observed when potassium silicate was applied three times at 0.2%.
CONCLUSION:
Carrying out three sprays of potassium sulphate (growth start, three weeks later and just after berry setting) at 0.2% gave an economical yield and fairly good berries quality of Superior grapevines grown under Upper Egypt conditions.