الفهرس 
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Abstract
Effect of Spraying Navel Orange Trees with some Antioxidants on Growth and Productivity
This study was carried out through two consecutive seasons (2016 and 2017) to investigate the effect of spraying with some antioxidants on vegetative growth, yield, fruit quality as well as nutritional status of twelve years old ‘Navel orange᾿ trees grafted on sour orange rootstock and grown in a private orange orchard in Qalyubia Governorate, Egypt cultivated in a silty clay loam soil. This experiment involved three antioxidant materials named (salicylic acid, citric acid and folic acid) and spraying by three levels of each of any antioxidants (250, 500 and 1000 ppm) plus control treatment spraying with tap water so the experiment included ten treatments. selected trees were sprayed three times (at the beginning of the growth cycle in March, after fruit setting in May and after June DROP in July) by aqueous solution of salicylic acid, citric acid and folic acid, whereas the control treatments were sprayed with water only.
Data obtained could be summarized as follows:
1- Vegetative growth measurements
1-1- Leaf area
All treatments effected significantly on leaf area but 1000 ppm citric acid gave the highest values of leaf area during 2016&2017 seasons and also in average of the two seasons.
1-2- Specific leaf area
All treatments effected significantly on specific leaf area but 1000 ppm citric acid gave the highest values of specific leaf area during 2016&2017 seasons and also in average of the two seasons.
1-3- Total chlorophyll
All treatments effected significantly on total chlorophyll but 500 ppm salicylic acid gave the highest values of total chlorophyll during 2016&2017 seasons and also in average of the two seasons.
1-4- Leaves fresh weight
All treatments effected significantly on leaves fresh weight but 250 ppm citric acid gave the highest values of leaves fresh weight during 2016&2017 seasons and also in average of the two seasons.
1-5- Leaves dry weight
All treatments effected significantly on leaves dry weight but 250 ppm citric acid gave the highest values of leaves dry weight during 2016&2017 seasons and also in average of the two seasons.
1-6- leaves dry matter %
All treatments effected significantly on leaves dry matter % but 1000 ppm salicylic acid gave the highest values of leaves dry matter % during 2016&2017 seasons and also in average of the two seasons.
And therefore, vegetative growth parameters of Navel orange trees were significantly increased by T2 (500 ppm salicylic acid), T6 (1000 ppm citric acid) and T8 (1000 ppm folic acid) through 2016, 2017 seasons and also as an average of the two growing seasons. Otherwise, in most cases T6 )1000 ppm citric acid) gave the highest vales of all vegetative growth parameters.
2- Yield measurements
2-1- Fruit DROP % monthly from May to October
Foliar spraying with 500 ppm salicylic acid gave the lowest values of fruit DROP % monthly from May to October during 2016&2017 seasons and also in average of the two seasons.
2-2- Fruit set % monthly from May to October
Foliar spraying with 500 ppm salicylic acid gave the highest values of fruit set % monthly from May to October during 2016&2017 seasons and also in average of the two seasons.
2-3- Retention fruit set %
Foliar spraying with 250 ppm salicylic acid gave the highest values of retention fruit set % during 2016&2017 seasons and also in average of the two seasons.
2-4- Fruit weight
All treatments effected significantly on fruit weight but 250 ppm salicylic acid followed by 250 ppm folic acid gave the highest values of fruit weight during 2016&2017 seasons and also in average of the two seasons.
2-5- Number fruit / tree
Foliar spraying with 500 ppm salicylic acid and also 500 ppm citric acid gave the highest values of number fruit / tree during 2016&2017 seasons and also in average of the two seasons.
2-6- Yield kg/tree
Foliar spraying with 500 ppm salicylic acid gave the highest values of yield (kg/tree) during 2016&2017 seasons and also in average of the two seasons.
And therefore, yield parameters were significantly increased by T2 (500 ppm salicylic acid), T5 (500 ppm citric acid) and T7 (250 ppm folic acid) in 2016, 2017 seasons and also as an average of the two seasons. In most cases T2 (500 ppm salicylic acid) was the superior treatment for all yield parameters.
3- Physical and chemical fruit characteristics
3-1- Fruit volume
All treatments effected significantly on fruit volume but 250 ppm folic acid gave the highest values of fruit volume during 2016&2017 seasons and also in average of the two seasons.
3-2- Fruit length
All treatments effected significantly on fruit length but 1000 ppm salicylic acid gave the highest values of fruit length during 2016&2017 seasons and also in average of the two seasons.
3-3- Fruit diameter
All treatments affected significantly on fruit diameter but 250 ppm folic acid gave the highest values of fruit diameter during 2016&2017 seasons and also in average of the two seasons.
3-4- Fruit shape index
There was no significant differences between all treatments and control treatment for fruit shape index values during 2016&2017 seasons, as for average of the two seasons there was a significant difference between all treatments and control treatment.
3-5- Peel thickness
All treatments effected significantly on peel thickness but 1000 ppm salicylic acid and also folic acid at 1000 ppm gave the least values of peel thickness during 2016&2017 seasons and also in average of the two seasons.
3-6- Peel weight
All treatments effected significantly on peel weight but 500 ppm salicylic acid and also 250 ppm citric acid ppm gave the least values of peel weight during 2016&2017 seasons and also in average of the two seasons.
3-7- Peel: fruit %
All treatments effected significantly on peel: fruit % but 500 ppm salicylic acid gave the least values of peel: fruit % during 2016&2017 seasons and also in average of the two seasons.
3-8- Pulp diameter
All treatments effected significantly on pulp diameter but 250 ppm folic acid gave the highest values of pulp diameter during 2016&2017 seasons and also in average of the two seasons.
3-9- Pulp weight
All treatments effected significantly on pulp weight but 500 ppm salicylic acid and also 250 ppm folic acid gave the highest values of pulp weight during 2016&2017 seasons and also in average of the two seasons.
3-10- Pulp: fruit %
All treatments effected significantly on pulp: fruit % but 500 ppm salicylic acid gave the highest values of pulp: fruit % during 2016&2017 seasons and also in average of the two seasons.
3-11- Juice volume
All treatments effected significantly on juice volume but 250 ppm salicylic acid gave the highest values of juice volume during 2016&2017 seasons and also in average of the two seasons.
3-12- Juice weight
All treatments effected significantly on juice weight but 500 ppm salicylic acid and also 250 and 500 ppm folic acid treatments gave the highest values of juice weight during 2016&2017 seasons and also in average of the two seasons.
3-13- Juice %
All treatments effected significantly on juice % but 250 ppm salicylic acid gave the highest values of juice % during 2016&2017 seasons and also in average of the two seasons.
3-14- T.S.S.
All treatments effected significantly on T.S.S. but 250 ppm citric acid gave the highest values of T.S.S. during 2016&2017 seasons and also in average of the two seasons.
3-15- Total acidity
All treatments effected significantly on total acidity but 250 ppm citric acid gave the least values of total acidity during 2016&2017 seasons and also in average of the two seasons.
3-16- T.S.S.: acid ratio
All treatments effected significantly on T.S.S.: acid ratio but 250 ppm citric acid gave the highest values of T.S.S.: acid ratio during 2016&2017 seasons and also in average of the two seasons.
3-17- Ascorbic acid (vitamin C)
All treatments effected significantly on vitamin C but 1000 ppm salicylic acid and also both 500 ppm citric acid and 500 ppm folic acid gave the highest values of vitamin C during 2016&2017 seasons and also in average of the two seasons.
And therefore, physical and chemical fruit characteristics of Navel orange trees were significantly increased by T2 (500 ppm salicylic acid), T4 (250 ppm citric acid) and T7 (250 ppm folic acid) in the first and second season followed by the average of the two seasons. Otherwise, in most cases T2 (500 ppm salicylic acid) gave the highest vales of all physical and chemical fruit characteristics.
4- Chemical analysis of leaves
4-1- Total protein %
Total protein % of Navel orange trees were significantly increased by the spraying trees with 500 ppm folic acid compared with salicylic and citric acid during 2016&2017 seasons and also in average of the two seasons.
4-2- Total phenolic compounds
Total phenolic compounds of Navel orange trees were significantly increased by the spraying trees with1000 ppm folic acid during 2016&2017 seasons and also in average of the two seasons.
4-3- Macronutrients %
Macronutrients percentage of Navel orange trees were significantly increased by folic acid treatments compared with salicylic and citric acid treatments especially spraying with 250 and 500 ppm folic acid.
4-4- Micronutrients content
Micronutrients concentration of Navel orange trees were significantly increased by the spraying trees with the third level of salicylic acid (1000 ppm) and the first level of folic acid (250 ppm).
Finally it could be concluded that, spraying with 500 ppm salicylic acid may be recommended from economical point of view and as good treatment for enhancing Navel orange growth, yield, fruit quality and nutritional status especially under old citrus orchards.