الفهرس 
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Abstract
This investigation was performed during two consecutive seasons of 2005/ 2006 (third ratoons) and 2006/ 2007 ( fourth ratoons) on Williams banana plants grown in a private orchard located at El- Nasyria village, Dear Mouas district, Minia Governorate. The soil texture is clay loam . All the selected Williams banana plants received the normal horticultural practices except those dealing with the antioxidant ascorbic acid, Mg, Zn and B application .
This study throw some light on the effects of ascorbic acid and three essential nutrients namely Mg, Zn and B on yield and fruit quality of Williams banana.
The present study consisted from two factors. The first factor comprised from five concentration of the antioxidant ascorbic acid namely 0.0 , 125, 250 , 500 or 1000 ppm. The second factor contained the following seven treatments from three essential nutrients ( Mg, Zn and B).
1-Untreating plants with nutrients ( water sprayed plants)
2-Spraying magnesium sulphate at 0.5 %.
3-Spraying chelated zinc at 0.05 %.
4- Spraying boric acid at 0.025 %.
5- Spraying magnesium sulphate + chelated zinc.
6- Spraying chelated zinc + boric acid.
7- Spraying all nutrients ( Mg+ Zn + B).
Therefore, the experiment included thirty five treatments. Each treatment replicated three times, one stool per each. One hundred and five stools were selected for achieving of this study. Ascorbic acid was sprayed four times during each season on the first week of May, June, July and August. The three nutrients ( Mg, Zn and B) were applied six times started at the first week of April and then at three weeks intervals (ended at the last week of July).
The experimental was set in a completely randomized block design in splite plot arrangement which the five concentrations of ascorbic acid ranked the main plots and the seven nutrient treatments occupied the sub- plots. Each treatment was represented by three stools for fruiting in the current season plus three suckers for fruiting in the following one.
For evaluating the impact of ascorbic acid concentrations and nutrients ( Mg, Zn and B) application on growth , nutritional status of plants, yield and fruit quality of Williams banana plants, the following parameters were measured during the two experimental seasons.
1-Height (cm.) and girth (cm.) of Pseudostem .
2-Total leaf area per plant ( m2)
3-Essential nutrients in the leaf namely N, P , K, Mg and Zn.
4-Yield / plant ( bunch weight) ( kg).
5-Average hand weight ( kg.)
6-Average weight (g.), length (cm.) and width (cm.) of finger.,
7-Percentages of pulp and peel in the fruit .
8-Pulp / peel.
9-Percntages of total soluble solids, total and reducing sugars, starch and total acidity in the pulp.
The nearly same results obtained in both seasons could be arranged under the following main items:
1-Vegetative growth characters:
Spraying ascorbic acid at 125 to 1000 ppm four times obviously stimulated the three investigated growth characters namely height and girth of pseudostem and total leaf area compared to the check treatment. The stimulation was associated with increasing ascorbic acid concentrations. Increasing concentrations of ascorbic acid from 500 to 1000 ppm had a slight promotion on these growth traits.
Treating Williams banana plants six times with magnesium, zinc and boron either singly or in combinations caused an obvious promotion on these growth characters compared to control treatment. Application of magnesium was the superior use of the other two nutrients in enhancing these growth characters. Combined application of the three nutrients resulted in maximizing these growth characters. Spraying ascorbic acid at 1000 ppm plus the three nutrients gave the maximum values.
2-Leaf contents of N, P, K, Mg and Zn:
Four sprays of ascorbic acid at 125 to 1000 ppm caused an obvious promotion on N, P, K, Mg and Zn in the leaves of Williams banana compared to the check treatment. Increasing concentrations was followed by a gradual promotion on these nutrients. Meaningless increase on the values of these nutrients was observed when concentrations of ascorbic acid was increased from 500 to 1000 ppm. Treating the plants with ascorbic acid at 1000 and 0.0 ppm gave the maximum and minimum values, respectively.
Single or combined application of these nutrients was accompanied with enhancing N, P, K, Mg and Zn in the leaves compared to non- application. Spraying Mg, Zn and B, in descending order was favourable in enhancing leaf content of these nutrients. The maximum values were recorded on plants received the three nutrients together. Untreated plants had the lowest values.
The highest values of N, P, K, Mg and Zn were recorded on plants treated four times with ascorbic acid at 500 ppm plus Mg, Zn and B six times.
3-Yield / plant ( bunch weight)
Yield per plant of Williams banana was positively affected by spraying ascorbic acid at 125 to 1000 ppm. The promotion was associated with increasing ascorbic acid concentrations Increasing ascorbic acid concentrations from 500 to 1000 ppm had negligible effect on the yield.
Yield of Williams banana plants was materially affected by single or combined application of Mg, Zn and B . Application of Mg surpassed the spray of Zn and B in this respect. The best results were obtained on plants received the three nutrients together.
from economical point of view, it is suggested to spray ascorbic acid four times at 500 ppm plus the three nutrients together six times for improving yield of Williams banana plants.
4-Hand weight:
Hand weight of Williams banana was progressively increased with increasing ascorbic acid concentrations from 125 to 1000 ppm. Considerable promotion on hand weight was detected among all concentrations except among the higher two concentrations namely 500 and 1000 ppm.
Single or combined application of Mg, Zn and B was obviously responsible for enhancing hand wight compared to the check treatment.
Spraying Mg, Zn and B, in descending order was accompanied with increasing hand weight. Spraying Mg, Zn and B together resulted in the maximum values.
The heaviest hands were recorded on plants received four sprays of ascorbic acid at 500 ppm plus six sprays of Mg, Zn and B.
5-Fruit quality characters:
Foliar application of ascorbic acid at 125 to 1000 ppm substantially enhanced finger weight and dimensions (width and length), percentages of pulp , pulp / peel , total soluble solids , total and reducing sugars, while reduced percentages of peel and total acidity compared to the check treatment. There was a remarkable promotion on fruit quality with increasing ascorbic acid concentrations . Increasing ascorbic acid concentration from 500 to 1000 ppm had a slight effect on fruit quality. Ascorbic acid treatment had no effect on starch in the pulp.
Treating Williams banana plants six times with Mg, Zn and B either singly or in combinations had an announced effect on improving fruit quality in terms of increasing fruit weight and dimensions , pulp weight and pulp / peel, total soluble solids % as well as total and reducing sugars and in decreasing peel weight % and total acidity %. The studied treatments had no effect on starch%.
Treating Williams banana four times with ascorbic acid at 500 ppm plus six times with Mg + Zn + B gave a striking effect on fruit quality.
Conclusion:
For obtaining an economical yield and promoting fruit quality, it advised to spray Williams banana plants four times with ascorbic acid ( at the first week of May, June, July and August) at 500 ppm and six times with a mixture of magnesium sulphate at 0.5 % , chelated zinc at 0.05 % and boric acid at 0.025 % ( at the first week of April and at three weeks intervals).