الفهرس 
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Abstract
This study was carried out during 2006 and 2007 seasons on Balady mandarin trees budded onto sour orange rootstock in a private orchard situated at Bany Suef district, Bany Suef Governorate. The selected trees are planted at 3.5 x 3.5 meters apart. The soil of the orchard is clay loam.
The objective of this experiment was to examine the effect of the two antioxidants namely ascorbic or citric acids at different concentrations on some vegetative growth characters, nutritional status of the trees, fruit retention %, yield as well as physical and chemical characters of Balady mandarin fruits ( Citrus reticulate Blanco).
The experiment included two factors: the first factor consisted from the two antioxidants namely, ascorbic and citric acids. While, the second factor contained the five concentrations of each antioxidant namely 0.0, 250, 500, 1000 and 2000 ppm .
Therefore, the experiment involved ten treatments. Each treatment was replicated three times, one tree per each. The two antioxidants at the previous concentrations were sprayed four times during each season on the middle of March, May, July and September at the early morning. Triton B as a wetting agent was added to all solutions of antioxidants. The trees were sprayed till runoff ( 20 L/ tree).
The experiment was set up in a complete randomized block design in split- plot arrangement. The two antioxidants and the five concentrations of each antioxidant main and the sub- plots, respectively.
During 2006 and 2007 seasons, the following characters were measured.
1-Some vegetative growth characters namely, number of leaves / shoot and leaf area (cm2) in the Spring growth cycle.
2-Percentages of N, P and K in the leaf of non- fruiting shoots in the Spring growth flush.
3-Percentages of initial fruit setting and fruit retention.
4-Yield expressed in weight (kg.) and number of fruits per tree.
5- Some physical characters of the fruits namely fruit weight (g.) and dimensions ( height and diameter, cm), fruit shape index value as well as fruit peel weight % and thickness (cm.)
6-Some chemical characters of the fruits namely percentages of total soluble solids, reducing and total sugars and total acidity, T.S.S./ acid and vitamin C content ( mg/ 100 ml juice).
The nearly similar obtained results for both seasons could be summarized under the following main items:-
1-The leaf area and number of leaves / shoot.
Foliar application of citric acid was favourable for stimulating leaf area, and number of leaves /shoot in the Spring growth cycle rather than using ascorbic acid.
There was a gradual and remarkable promotion on such two growth characters with increasing concentrations of the two antioxidants from 0.0 to 2000 ppm. Increasing concentrations from 1000 to 2000 ppm failed to show any material increase on such two growth characters.
Treating Balady mandarin trees four times with citric acid at 2000 ppm resulted in the maximum values. The minimum values were recorded on untreated trees.
2-Percentages of N, P and K in the leaf:
Percentages of N, P and K in the leaf were considerably increased in the trees treated with citric acid rather than those sprayed with ascorbic acid.
Spraying the trees with ascorbic or citric acids at 250 to 2000 ppm caused a material promotion on such essential nutrients compared to the check treatment. The promotion was associated with increasing concentrations. Meaningless increase on these nutrients was recorded when concentrations of the two antioxidants were increased from 1000 to 2000 ppm.
The maximum and minimum values were recorded on the trees received citric acid at 2000 ppm and on the untreated trees, respectively.
3-Percentages of initial fruit setting and fruit retention:
Spraying Balady mandarin trees four times with citric acid was preferable in improving percentages of initial fruit setting and fruit retention than using ascorbic acid.
A remarkable promotion on percentages of initial fruit setting and fruit retention was observed due to spraying the two antioxidants at 250 to 2000 ppm compared to the check treatment. The promotion was associated with increasing concentrations of each antioxidant. A slight increase was observed among the two higher concentrations.
4-Yield:
It was obviously improved in response to application of citric acid compared to using ascorbic acid.
There was a progressive promotion on the yield expressed in weight (kg) and number of fruits per trees with increasing concentrations of the two antioxidants. Increasing concentrations from 1000 to 2000 ppm caused a slight increment on the yield. Therefore, the recommended concentration responsible for gaining an economical yield was 1000 ppm.
For obtaining an economical yield of Balady mandarin trees growing under middle Egypt conditions, it is suggested to spray the trees four times with citric acid at 1000 ppm.
5-Physical and chemical characters of the fruits:
Treating Balady mandarin trees with citric acid was preferable then using ascorbic acid in improving fruit quality in terms of increasing fruit weight and dimensions, total soluble solids %, total and reducing sugars %,. T.S.S./ acid and vitamin C content and in decreasing fruit peel weight and thickness and total acidity . Shape of fruit did not change with citric and ascorbic acid treatments.
Increasing concentrations of the two antioxidants from 0.0 to 2000 ppm caused a remarked promotion on fruit quality as compared with non- application. The promotion on physical and chemical properties of the fruits was associated with increasing concentrations. Considerable promotion on fruit quality was observed among all concentrations except between the two higher concentrations namely 1000 and 2000 ppm.
Spraying Balady mandarin trees four times with citric acid at 1000 ppm from economical point of view gave the best results with regard to fruit quality