الفهرس 
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Abstract
This study was carried out during 2014 and 2015 seasons on 150 uniform in vigour own-rooted 13-year old Superior grapevines grown in a private vineyard located at Abwan village, Matay district, Minia Governorate where the texture of the soil is clay, well drained and water table not less than two meters deep. All the selected vines are planted at 2 x 3 m apart. The chosen vines (150 vines) were pruned during the first week of January in the two seasons using cane pruning method with the assistance of Gable supporting system. Vine load was differed according to the present treatments. Surface irrigation system was followed using Nile water containing 150 ppm EC. The selected vines received the same and common horticultural practices that already applied in the vineyard except those dealing with pruning and application of citric acid.
The main target of this study was examining the effect of different vine loads and foliar application of citric acid on some growth traits, nutritional status of the vines, yield and quality of Superior grapes.
This study included twenty-five treatments from two factors (A&B). The first factor (A) contained the following five levels of vine loads:-
a1) Leaving 62 eyes/vine (on the basis of five fruiting canes X 10 eyes plus six renewal spurs X 2 eyes).
a2) Leaving 72 eyes/vine (on the basis of six fruiting canes X 10 eyes plus six renewal spurs X 2 eyes).
a3) Leaving 82 eyes/vine (on the basis of seven fruiting canes X 10 eyes plus six renewal spurs X 2 eyes).
a4) Leaving 92 eyes/vine (on the basis of eight fruiting canes X 10 eyes plus six renewal spurs X 2 eyes).
a5) Leaving 102 eyes/vine (on the basis of nine fruiting canes X 10 eyes plus six renewal spurs X 2 eyes).
The second factor (B) included the following five concentrations of citric acid: b1) 0.0%, b2)0.05%, b3)0.1%, b4)0.2% and b5)0.4%. Each treatment was replicated three times, two vines per each.
Winter pruning of the vines was carried out at the first week of Jan. during 2014 and 2015 seasons. Citric acid was sprayed three times at growth start (last week of Feb.), just after berry setting stage (mid. of Apr.) and at three weeks later (1st week of May).
Triton B as a wetting agent was added to all citric acid solutions at 0.05%. Spraying was established till runoff (2L solution/vine). Control treatment was sprayed with water containing Triton B.
Randomized complete block design (RCBD) in splite plot arrangement was followed. The first factor (five vine loads) occupied the main plots and the second one (five concentrations of citric acid) ranked the subplots. The experiment consisted of twenty-five treatments, each treatment was replicated three times, two vine per each.
During both seasons, the following parameters were recorded:
1- Behaviors of buds including percentages of bud burst, fruiting buds and bud fertility.
2- Vegetative growth characteristics namely main shoot length (cm), number of leaves/shoot, leaf area, wood ripening coefficient, pruning wood weight per vine (kg.) and cane thickness (cm).
3- Chlorophylls a & b and total chlorophylls mg/100g F.W).
4- Percentages of N, P, K, Mg in the leaves on dry weight basis.
5- Percentage of berry setting, yield expressed as weight (kg) and number of clusters per vine as well as weight, length shoulder and compactness (cm) of cluster.
6- Percentage of shot berries.
7- Physical and chemical characteristics of the berries namely berry weight and dimensions (longitudinal and equatorial, in cm), juice%, T.S.S.%, titratable acidity % as g tartaric acid/100 ml juice, reducing sugars% and T.S.S./acid.
The nearly same obtained data during both seasons could be summarized under the following main topics:
1- Behavior of buds:
Increasing vine loads from 62 to 102 eyes/vines caused a gradual promotion on the percentage of fruiting buds and a reduction on both the percentages of bud burst and bud fertility. Citric acid treatment had no effect on bud behavior parameters. The highest values of percentage of fruiting buds were recorded with leaving 102 eyes/vine. Leaving 62 eyes/vine resulted in the minimum percentages of buds burst and bud fertility.
2- Vegetative growth characteristics:
Increasing vine loads from 62 to 102 eyes/vines caused a progressive promotion on the leaf area, pruning wood weight and cane thickness and caused a reduction on main shoot length, number of leaves/shoot and wood ripening coefficient. Leaving 102 eyes/vine maximized the leaf area, pruning wood weight and cane thickness and minimized main shoot length, number of leaves/shoot and wood ripening coefficient.
Spraying citric acid at 0.05 to 0.4% stimulated all the previous six growth characteristics over the control treatment. The promotion was associated with increasing concentrations of citric acid. Meaningless promotion on such growth aspects was observed among the higher two concentrations of citric acid namely 0.2 and 0.4%.
The highest values of leaf area, pruning wood weight and cane thickness and the minimum values of main shoot length, number of leaves/shoot and wood ripening coefficient were recorded due to leaving 102 eyes/vine plus spraying citric acid at 0.4%.
3- Percentages of berry setting, yield and cluster aspects:
There was a gradual promotion on the percentage of berry setting, yield as well as weight, length shoulder and compactness of cluster with increasing vine loads from 62 to 102 eyes/vine. A clear and gradually promotion on these parameters was observed due to spraying citric acid at 0.05 to 0.4% over the untreated vines. The promotion on these parameters was related to the increase in citric acid concentrations without considerable promotion among the higher two concentrations namely 0.2 and 0.4%.
The best results with regard to berry setting %, yield, number of clusters/vine and weight, length, shoulder and compactness of cluster were obtained when pruning was carried out by leaving 102 eyes/vine as well as spraying citric acid at 0.2% (since no major differences were observed on these parameters among the use of 0.2 and 0.4%), from economical point of view.
4- Percentages of shot berries:
An obvious and gradual promotion on the percentage of shot berries was noticed with increasing vine loads from 62 to 102 eyes/vine. Increasing concentrations of citric acid from 0.05 to 0.4% had negative effect on such characteristic. The reduction was depended on increasing concentrations of citric acid from 0.05 to 0.4%.
No considerable reduction on the percentage of shot berries was detected among the higher two concentrations namely 0.2 and 0.4%.
The lowest values of shot berries% were recorded with carrying out pruning leaving 62 eyes/vine plus spraying citric acid at 0.4%. Pruning to leave 102 eyes/vine without using citric acid gave the highest values.
5- Physical and chemical characteristics of the berries:
Increasing vine loads from 62 to 102 eyes/vine was accompanied with a gradual reduction on weight, longitudinal and equatorial of berry, juice% and titratable acidity% and caused a promotion on T.S.S.%, T.S.S/acid and reducing sugars%.
Treating the vines with citric acid at 0.05 to 0.4% caused an obvious promotion on quality of the berries in term of increasing weight, longitudinal and equatorial of berry, juice%, T.S.S.%, T.S.S/acid and reducing sugars% and decreasing titratable acidity% over the control treatment. The promotion was related to the increase in concentrations of citric acid.
from economical point of view, the best results with regard to chemical quality of the berries were obtained with pruning leaving 102 eyes/vine plus spraying citric acid at 0.2%. Leaving 62 eyes/vine plus spraying citric acid at 0.2% gave favourable effects on physical characteristics of the berries.
Conclusion:
The best results with regard to yield and chemical fruit quality of Superior grapevine grown under Minia region conditions were obtained by leaving 102 eyes (on the basis of nine fruiting cane X ten eyes plus six renewal spur X two eyes) during winter pruning plus spraying citric acid at 0.2% three times (at growth start, just after berry setting and three weeks later).