الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The present experiment was conducted during the three successive seasons of 2011, 2012 and 2013, at a private orchard located at Cairo-Alexandria desert road (km. 76 Cairo – Alex).
The aim of this experiment was to study the response of Keitt mango trees to different nitrogen and potassium fertilization levels under shading and non-shading conditions.
The obtained results could be summarized as follows:
Shade treatments on growth and chemical composition of Keitt Mango Trees:
Vegetative growth:
1. The significantly highest values of trees height increment percentage, leaf area and dry mater percentage were found under shading condition compared to those under open field condition in all studied seasons.
2. Trunk diameter increment percentage and chlorophyll content under screenhouse condition were significantly higher compared to those on open field condition in all seasons except third season.
Chemical characteristics
Leaf mineral content
3. The screenhouse condition recorded higher nitrogen percent in leaves more than open field condition, except, first season.
4. Growing mango under screenhouse gave the highest content of potassium, sulfur, iron, zinc, manganese, copper and cobalt in leaves for the three seasons.
5. Trees under shading condition significantly recorded highest leaf magnesium and calcium percentage compared to those on open field condition in the second season only.
Flowering characteristics
6. They bloom dates were always earlier inside the screenhouse than outside the open field during the three studied seasons.
7. Treatment shading condition manifested highest significant value of number of panicle and panicle longer compared to those under open field condition for all studied seasons.
Fruiting
8. Trees under screenhouse net led to significant increase in initial number of fruit set / panicle and number of fruits retained / panicle during the three seasons gained highest fruit set compared to trees grown under open field condition.
9. Trees under shading achieved the least value of fruit DROP percentage during all studied seasons.
10. Trees under shading achieved the highest value of fruit retention percentage during all studied seasons.
11. The number of fruits/tree and yield were significantly affected by applied screenhouse treatment compared with open filed treatment during the three growing seasons.
Fruit characteristics
12. Highest values of fruit weight and fruit volume found with screenhouse compared to those under open field condition in three tested seasons.
13. The application of shading condition led to significant increase in fruit width during first and second season only.
14. Mango trees cultivated under screenhouse condition gave the higher values for pulp weight and pulp thickness than the open field condition. These results were true in three growing seasons.
Fruit chemical characteristics
15. Trees under shading condition significantly recorded highest nitrogen, iron, zinic, magnesium, sulfur and copper in fruits pulp compared to those on open field conditions.
16. The screenhouse treatment increased mango fruits pulp from potassium and calcium percent more than open field treatment in the first and third seasons, respectively. No significant influence was found in second season.
17. Trees under shading condition significantly recorded highest phosphorus percentage in fruits pulp compared to those on open field conditions except for first season.
18. The application of shading condition increased mango fruits pulp from manganese percent more than open field treatment in first and second seasons, respectively, no significant influence was found in third season.
19. Trees under shading condition significantly recorded highest total soluble solids and total acidity in fruits value compared to those on open field conditions except for second season.
20. The screenhouse condition produced higher fruits content from ascorbic acid, total sugars and reducing sugars more than open filed condition through three growing seasons.
21. Trees under shading condition achieved higher significant value of total phenol, crude fiber content and moisture percentage in fruits pulp than those under open field conditions.
22. The screenhouse treatment had no significant influences on dry mater percentage fruit all over the tested growing seasons, except second season.
Hormonal content in February
23. The screenhouse net recorded lowest ABA content in buds compared with open field conditions.
24. The bud content of zeatin and benzyl adenine hormone in buds were higher at screenhouse treatment than other treatment.
Hormonal content in October
25. The screenhouse condition lead to increase the zeatin and benzyl adenine content in buds compared with open field condition.
Interaction between fertilization treatments and shading conditions on growth and chemical composition of Keitt Mango Trees:
Vegetative growth:
1. The highest significant value of tree height increment percentage was found in trees fertilized by 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under screenhouse condition, 150 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field condition and 120 kg/feddan of nitrogen + 100 kg/feddan of potassium under open field during the three seasons; respectively.
2. The highest significant value of trunk diameter was recorded by 120 kg/feddan of nitrogen + 100 kg/feddan of potassium under screenhouse condition in the first and third seasons but 120 kg/feddan of nitrogen + 80 kg/feddan of potassium under screenhouse condition in the second season. While, 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under open field had the lowest significant value in the first and second seasons and 150 kg/feddan of nitrogen + 80 kg/feddan of potassium under screenhouse condition in the third season.
3. The highest significant value of leaf area was obtained by 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under shading condition had the highest significant values in all seasons. In contrast, 80 kg/feddan of nitrogen + 100 kg/feddan of potassium under open field in the first season gave low significant value but 80 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field recorded the lowest significant values in second and third seasons.
4. The highest value leaf dry matter percentage and chlorophyll content (SPAD) got from 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under shading condition. Whereas, the lowest dry mater percentage was found by 80 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field in the three seasons of study.
Flowering characteristics
5. Number of panicle/tree, panicle width and length were highest significant value by 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under shading condition. Whereas, the lowest value was found by 80 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field during the three season of study.
6. Pollen viability inside the screenhouse was always higher than those open filed the screenhouse. This trend of results was confirmed throughout the three studied seasons.
Fruiting
7. Fruit DROP due to application of fertilizer treatments and shading condition differ significantly in all season. The trees fertilized with 80 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field condition manifested the maximum value in both three seasons.
8. The treatment 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under shading condition resulted the highest fruit retention percentage during growing seasons.
Yield
9. The highest number of fruits/tree was obtained by screenhouse condition with 150 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment. Whereas, open field and screenhouse conditions with 80 kg/feddan of nitrogen + 80 kg/feddan lead to decrease it at all tested seasons.
10. The highest significant yield was cleared that the treatment 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under shading conditions during all studied seasons. Whereas, the lowest yield was obtained from the treatment combination of 80 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field condition during the 1st and the 3rd seasons but under screenhouse condition in the second season only.
Fruit characteristics
11. The treatment of nitrogen at 150 kg/feddan + potassium at 100kg/feddan under shading condition had the highest significant fruit weight, fruit volume, fruit length, fruit width and fruit thickness in all studied seasons. While, the lowest values were obtained from the treatment combination of nitrogen at 80kg/feddan + potassium at 80 kg/feddan under open field condition in all three seasons.
12. The highest value of flesh firmness was observed with application treatment control under screenhouse treatment. These was true at all growing seasons.
13. The highest fruit peel color was achieved with trees received 150 kg/feddan of nitrogen +100 kg/feddan of potassium under open field condition, 120 kg/feddan of nitrogen +80 kg/feddan of potassium under screenhouse condition and 80 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field condition in the first, second and third seasons, respectively.
14. Plants fertilized by 80 kg/feddan of nitrogen + 80 kg/feddan of potassium with open field condition recorded the least value of hue angle was the most effective treatment in increasing pulp color from green to yellow and orange color in the 1st, 2nd and 3rd season, respectively. While, 120 kg/feddan of nitrogen + 100 kg/feddan of potassium with screenhouse condition recorded the lowest pulp color in the third season.
15. The higher significant value of peel weight and pulp weight were recorded in trees by 150 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment under screenhouse treatment than most of other treatments, whereas, 80 kg/feddan of nitrogen + 80 kg/feddan of potassium treatment with open field treatment gave the lowest significant values. Same result was found in the first, second and third seasons except peel weight values in the third season, the control treatment with open filed treatment indicated the lowest value.
16. The seed weight increased with applying screenhouse treatment with 80 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment and 120 kg/feddan of nitrogen + 80 kg/feddan of potassium treatment at first, second seasons, respectively but 120 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment under open field condition in the third seasons.
17. Treatment 150 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment with screenhouse condition leaded to increase pulp thickness more than of other treatments. This result was observed in three tested seasons.
Fruit chemical characteristics
Fruit mineral percentage
18. The application of 150 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment with screenhouse condition gave highest N, P, Fe, Zn, S and Mg content in mango fruits pulp, except, Ca and Mn in the second and third seasons, respectively, 150 kg/feddan of nitrogen + 100 kg/feddan of potassium with open field conditions gave the highest percent.
19. No significant influence was found between fertilization treatments under screenhouse or open field conditions in potassium percent in mango fruits pulp at the first and second seasons, respectively.
20. The highest values of total soluble solids were achieved by 120 kg/feddan of nitrogen + 100 kg/feddan of potassium under shading condition during the first and the third seasons while, 120 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field conditions in the second season.
21. Maximum total acidity value was observed with 120 kg/feddan of nitrogen + 100 kg/feddan of potassium under screenhouse condition in the first and the third seasons while, 120 kg/feddan of nitrogen + 80 kg/feddan of potassium under screenhouse condition in the second season showed higher significant values than some of other treatments.
22. The greatest value of TSS/acid ratio was obtained with 80 kg/feddan of nitrogen+ 80 kg/ feddan of potassium with open field condition in the first and third seasons, whereas, control treatment in the second season.
23. The control treatment under screenhouse condition attained maximum ascorbic acid content in the three growing seasons.
24. The total sugars content and reducing sugars were significant between the two studied factors. The best treatment was obtained with 150 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment under screenhouse conditions.
25. The obtained results showed that non-reducing sugars content was not significantly affected by fertilization treatments under open filed and screenhouse conditions, except first and second seasons. The most favorable treatments for increasing the non-reducing sugars in the first season with 80 kg/feddan of nitrogen + 80 kg/feddan of potassium, 80 kg/feddan of nitrogen + 100 kg/feddan of potassium, 120 kg/feddan of nitrogen + 80 kg/feddan of potassium, 120 kg/feddan of nitrogen + 100 kg/feddan of potassium treatments under open field condition without significant difference. In the second season, 120 kg/feddan of nitrogen + 80 kg/feddan of potassium treatment under open field conditions.
26. The results indicated that control treatment under screenhouse registered the highest significant total phenol content.
27. Crude fiber content was increased by 80 kg/feddan of nitrogen+ 80 kg/ feddan of potassium treatment with open filed treatment.
28. The fertilization treatments under open field or shading conditions were found no significant effects on nitrate and nitrite (mg/kg) of mango.
29. The Results indicated that trees which grown under screenhouse with 150 kg/feddan of nitrogen+ 100 kg/ feddan of potassium treatment recorded the highest moisture percentage.
30. The greatest flesh dry mater percentage in fruits pulp of mango in the first season obtained with 150 kg/feddan of nitrogen+ 100 kg/ feddan of potassium treatment under open field conditions. While, in the second and third seasons 150 kg/feddan of nitrogen+ 100 kg/ feddan of potassium treatment under screenhouse condition gave the greatest values.
Leaf mineral content:
31. The treatment 150 kg/feddan of nitrogen+100 kg/feddan of potassium under screenhouse conditition manifested the highest values nitrogen, potassium, iron, zinc, calcium, magnesium, manganese, copper and cobalt in leaves through the three tested seasons.
32. The most convenient treatments for increasing the phosphorus percentage in leaves was 150 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment under open field condition in the first and third seasons. whilst, In the second season, 150 kg/feddan of nitrogen + 80 kg/feddan of potassium treatment showed the highest value under screenhouse condition.
33. The highest sulfur percentage in leaves of mango trees was noticed by 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under screenhouse condition.
Hormonal content in February
34. The highest ABA content in mango buds was recorded in trees received treatment control under open field condition, followed by 150 kg/feddan of nitrogen + 80 kg/feddan of potassium treatment under open field condition. This trend was found in first and second seasons but 80 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field in third season.
35. IAA content in mango buds was increased by application 80 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment under open field condition. This trend was found in all growing seasons.
36. The greatest GA3 , benzyl adenine and 2IP hormone content obtained by 150 kg/feddan of nitrogen + 80 kg/feddan of potassium treatment under screenhouse. These results were true at all growing seasons.
37. The heights values of zeatin content in buds obtained by 150 kg/feddan of nitrogen + 100 kg/feddan of potassium under screenhouse condition and followed by 150 kg/feddan of nitrogen + 80 kg/feddan of potassium with screenhouse condition during all studied seasons.
38. The highest values of kintin hormone content was noticed with control treatment with screenhouse condition.
Hormonal content in October
39. The highest values of abscisic acid hormone content obtained by 100 kg/feddan of nitrogen + 100 kg/feddan of potassium under screenhouse condition in first and second seasons. Nevertheless, in third season, 120 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment under open field treatment increased it.
40. The obtained results noticed that 80 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment under open field condition had highest content of IAA hormone. These results were true in first and second seasons but 120 kg/feddan of nitrogen + 80 kg/feddan of potassium under open field in third season.
41. The highest gibberellin hormone content observed by 100 kg/feddan of nitrogen+ 80 kg/feddan of potassium treatment under open field condition at three growing seasons.
42. 150 kg/feddan of nitrogen+ 100 kg/feddan of potassium treatment under screenhouse condition obtained the highest zeatin of hormone content in second and third seasons. But, 100 kg/feddan of nitrogen+ 100 kg/feddan of potassium treatment under screenhouse treatment increased it in first season.
43. Mango trees grown in screenhouse condition with 100 kg/feddan of nitrogen + 100 kg/feddan of potassium treatment recorded the highest content of kintin hormone through first and second growing seasons. While, control treatment under open field condition showed the highest value in third season.
44. The highest values of benzyl adenine and 2IP hormones content got form application 150 kg/feddan of nitrogen + 80 kg/feddan of potassium treatment under screenhouse condition.
CONCLUSION
Its concluded that, applying screen net over mango trees modify the climatic condition under the screenhouse and around mango trees. Micro- climate under screenhouse characterized by lower air temperature and high relative humidity. Such modified microclimate enhancing all vegetative growth characteristics in trees under screenhouse compared to those cultivated under open field condition. As well as, increase flowering, pollen viability percentage, fruit set, fruit retention percentage, number of fruits/ tree and fruit weight. The enhancement in both vegetative and flowering characteristics reflected directly in higher fruit yield and fruit quality compared to open field.
Moreover, it concluded that, use the fertilization formula containing 150 kg/feddan of nitrogen mixed with 100 kg/feddan of potassium. This formula due to all obtained increments in vegetative growth, flowering and the total yield.
Concerning the interaction, under the circumstances of this study its clearly conclusion that, interaction between screenhouse climatic condition and the 150 kg/feddan of nitrogen mixed with 100 kg/feddan of potassium as a fertilization formula was the best in enhancing most of the studied parameters and presented the best fruit yield with high quality.