الفهرس 
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Abstract
This study was carried out during 2007 and 2008 seasons on Taimour mango trees onto Balady mango rootstock in a private orchard situated at Gerga district, Sohag Governorate where the soil is clay well drained and water Table depth not less than two meters. The selected trees are planted at 4× 4 meters apart.
This study throw some light on the effects of different concentrations and frequencies of seaweed extract on leaf area, nutritional status of the trees, yield as well as physical and chemical characters of Taimour mango fruits. Seaweed extract contains Ascophyllum nodosum alga exudates, 60 nutrients, 21 amino acids, IAA, GA3, cytokinins, organic acids, vitamins and some antioxidants.
The experiment included two factors (A & B). The first factor (A) contained four concentrations of seaweed extract namely 0.0 , 0.05 , 0.1 and 0.2 % . The three treatments of seaweed frequencies i.e three (growth start , just after fruit setting and at two weeks later), four (the same previous three dates and at two weeks later) or five (the same previous four dates and at two weeks later) occupied the second factor (B). Therefore, the experiment involved twelve treatments. Each treatment replicated three times, one tree per each.
Completely randomized block design in split-plot arrangement was adopted. The four concentrations and three treatments of seaweed extract frequencies ranked the main and subplots, respectively.
For studying the various effects of concentrations and frequencies of seaweed extract on Taimour mango trees during the two experimental seasons, the following measurements were recorded:
1- Leaf area in the Spring growth cycle cm2 .
2- Percentages of N, P, and K in the leaves from non-fruiting shoots in the Spring growth cycle.
3- Percentage of 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 (length , width and thickness , in cm.), percentage of pulp , peel and seed in the fruit, edible to non-edible portions in the fruit.
6- Some Chemical quality of the fruits namely total soluble solids %, total acidity %, total and reducing sugars %, and vitamin C content (mg / 100 g pulp) .
The nearly same obtained results in both seasons could be summarized under the following main items.
1- Leaf area and its content of N , P and K.
Foliar application of seaweed extract at 0.05 to 0.2 % caused a material stimulation on the leaf area and its content of N, P and K rather than non-application. The promotion was associated with increasing concentrations of such biostimulant. Meaningless promotion on the leaf area and its content of N, P and K was observed among the higher two concentrations of seaweed extract (0.1 and 0.2 %). The minimum values were recorded on untreated trees.
There was a remarkable promotion on the leaf area and its content of N, P and K with increasing frequencies of seaweed extract from three to five sprays. Increasing number of sprays from four to five sprays had negligible increase on these parameters. Spraying the trees three times with seaweed extract effectively minimized these parameters.
The maximum values were recorded on the trees received five sprays of seaweed extract at 0.2 %. Untreating the trees produced the minimum values.
2- Percentage of fruit retention and yield.
Percentage of fruit retention and yield expressed in weight (kg.) and number of fruits per tree were positively affected by application of seaweed extract at 0.05 to 0.2 % compared to non-application. Yield and percentage of fruit retention were gradually promoted in response to increasing concentrations of seaweed extract from 0.05 to 0.2 %. Increasing concentrations from 0.1 to 0.2 % failed to show considerable effect on fruit retention and yield. Therefore, the recommended concentration was 0.1 %. Economically point of view spraying the trees with seaweed extract at 0.1 % produced noticeable yield. The lowest yield was recorded on untreated trees.
Fruit retention % as well as yield and number of fruits per tree were progressively improved in response to increasing seaweed frequencies from three to five sprays. The promotion was slight among the application of seaweed extract either four or five sprays. The minimum and maximum values were recorded on the trees received three and five sprays, respectively . The recommended number of sprays seaweed extract from economical point of view was four sprays.
Carrying four sprays of seaweed extract at 0.1 % is suggested to be very beneficial for obtaining an economical yield of Taimour mango trees. The lowest values were detected on the check trees.
3- Fruit quality .
Spraying seaweed extract at 0.05 to 0.2 % was accompanied with enhancing physical and chemical characters of Taimour mango fruits in terms of increasing fruit weight and dimensions (Length, width and thickness), percentage of pulp, edible to non edible portions in the fruit, total soluble solids, total and reducing sugars % and vitamin C content and in decreasing percentages of peel and total acidity % rather than non-application. The promotion was associated with increasing concentrations from 0.05 to 0.2 % Meaningless promotion was recorded among the higher two concentration, therefore, the recommended concentrations was 0.1 %. Varying concentrations had no effect on seed percentage.
There was a gradual promotion on fruit quality with increasing number of sprays seaweed extract from three to five sprays. There was a slight stimulation on fruit quality with increasing number of sprays seaweed extract from four to five sprays. Therefore the recommended number of sprays seaweed extract was four sprays. Number of sprays had no effect on seed weight .
Conducting four sprays of seaweed extract at 0.1 % was essential for causing an great improve in fruit quality.