الفهرس 
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Abstract
This study was carried out during 2005 and 2006 successive seasons on Balady mandarin trees budded onto sour orange rootstock and grown in a private citrus orchared situated at El-Basha Farm, Abou Korkas district, Minia Governorate. Water Table depth was more than two meters. The texture of the tested soil is silty clay. The trees are planted at 3.5x 3.5 meters apart.
The goal of this study was examining the effect of inorganic, organic bio and slow release N fertilizers on fruiting of Balady mandarin trees.
The present experiment included two factors ( A & B). The first factor (A) consisted form the two sources of nitrogen namely a1) fast release N fertilizer (Ammonium nitrate, 33.5% N) and a2)The slow release N fertilizer Enciabene (40% N). The second factor (B) comprised from the following six treatments from inorganic, organic and bioforms of N:
b1-Application of the recommended rate of i.e 1000g N /tree ( R.R.) completely via inorganic, form ( ammonium nitrate or Enciabene).
b2-Application of 75% of R.R. via inorganic ( ammonium nitrate or Enciabene) N plus 25% of R.R. via organic form ( compost El- Neel).
b3-Application of 50% of R.R. via inorganic form (ammonium nitrate or Enciabene ) plus 50% of R.R. via organic form (compost El-Neel)
b4-Application of 50% of R.R. via inorganic form ( ammonium nitrate or Enciabene) plus 12.5% of R.R. via organic form (compost El-Neel) plus 37.5% of RR via N bioform( Biogen)
b5-Application of 50% of R.R. via inorganic form ( ammonium nitrate or Enciabene) plus 25% of R.R. via inorganic ( compost El-Neel) +25% of R.R. via bioform ( Biogen)
b6- Application of 25% of R.R. via organic form ( ammonium nitrate or Enciabene) plus 37.5% of R.R. via organic form ( compost El-Neel) plus 37.5% of RR via bioform ( Biogen).
Therefore, the experiment involved 12 treatments (2x6). Each treatment was replicated three times, one tree per each. The organic N fertilizer Compost El-Neel (2.15% N) at various levels (5.82, 11.63, 17.45 and 23.26 kg/tree) was added once at the last week of January. The biofertilizer Biogen and the slow release N fertilizer Enciabene were added once at Spring growth start ( 1st week of March). Ammonium nitrate as a fast release N fertilizer was splitted into four equal batches and added on the first week of March, May, July and September. Biogen as a biofertilizer containing Azotabacter (1cm. contains 10-7 cell) was brought fresh and immediately used by mixing with moist sand before application. All fertilizers were added around each tree 50 cm. apart from the trunk in digs followed by covering with the soil then the orchard was irrigated.
Completely randomized block design in split plot arrangement was followed where the two N sources occupied the main plots and the six treatments from inorganic, organic and bioforms of N ranked the subplots.
In both the two seasons the following measurements were carried out:
1- Leaf area (cm2)
2- Percentages of N, P and K in the leaves.
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 weight (g), height and diameter of fruit (cm.), fruit shape value, fruit peel weight and thickness (cm.).
6- Some chemical characters of the fruits namely total soluble solids, total acidity ( as g citric acid / 100 ml juice), T.S.S / acid, total and reducing sugars and ascorbic acid content ( mg/ 100 ml juice).
The nearly same obtained data in both seasons could be summarized under the following main items:
1-leaf area (cm2)
It was greatly varied with using fast or slow release N fertilizers .Fertilizing the trees with N as inorganic slow release N fertilizers resulted in an obvious stimulation on the leaf area rather than using the fast one.
Application of the recommended rate of N via inorganic at 50 to 75% along with organic form or application of N through the three sources resulted in great stimulation on the leaf area compared to using N completely via inorganic form.
A great reduction on the leaf area was observed with using N as 25% inorganic + 37.50 % organic + 37.5% bioform. Fertilizing the trees with N as 50% inorganic fertilizer + 25% organic +25% biofertilizer gave the maximum leaf area.
Supplying Balady mandarin trees with N as 50 % inorganic slow release N fertilizer (Enciabene) + 25% compost El-Neel + 25% Biogen gave the maximum values.The minimum values were recorded on the trees received N as 25% ammonium nitrate + 37.5% compost El-Neel + 37.5% Biogen.
2- Leaf chemical composition:
The two essential nutrients namely P and K were remarkably reduced in response to supplying the trees with the slow release N fertilizer rather than using the fast one. However, N in the leaves was greatly promoted with using the slow release N fertilizer compared to using the soluble fertilizer.
Supplying the trees with N as 50 to 75% inorganic plus 25 to 50% organic and biofertilization was essential for enhancing N, P and K in the leaves compared to using N completely via inorganic form or using mineral N at percentages lower than 50% or using organic and biofertilization at percentages higher than 50%. A great decline on these nutrients was observed when the trees received N as 25% inorganic + 37.5% organic + 37.5% bioform.
Amending the trees with N as 50% via slow inorganic form + 25% organic + 25% bioform gave the maximum N and the minimum P and K in the leaves of the trees.
3-Percentages of initial fruit setting and fruit retention
There was a remarkable promotion on percentages of initial fruit setting and fruit retention with fertilizing of the trees with N as slow release N fertilizer rather than application of N as fast one.
Varying sources of N had an announced effect on percentages of initial fruit setting and fruit retention. Application of N through 50 to 75% inorganic plus organic fertilizer only or using N at the three sources of N effective by enhanced the two percentages compared to using N completely via inorganic fertilizer. The promotion was associated with decreasing inorganic percentages till 50% and at the same time increasing percentages of organic and biofertilization. Using inorganic N at percentages lower than 50% resulted in great reduction on these two characters.
The maximum values were recorded on the trees received N as 50% inorganic slow release N fertilizer plus 25% Compost El-Neel + 25% Biogen. Using the recommended rate of N completely via fast release inorganic N fertilizer gave the minimum values.
4- Yield per tree:
Yield of Balady mandarin trees expressed in weight ( kg.) and number of fruits per tree was positively affected by application of the slow release N fertilizer than application of the fast one.
Application of N in inorganic and organic form as well as in the three sources as 50 to 75% inorganic plus 25+ 50% organic and biofertilization was accompanied with improving the yield compared to using N completely via inorganic fertilizer. A great decline on the yield was observed when the trees received N as 25% inorganic + 37.5% organic + 37.5% bioform.
The maximum yield was recorded when the trees received N as 50% slow release N fertilizer plus 25% organic and 25% biofertilizer.Amending the trees with N via 100% soluble N fertilizer gave the minimum values.
5- Physical and chemical characters of the fruits:
They were improved in response to application of N via slow release N fertilizer compared to using N via the fast one. Fruit shape did not alter with the present treatments.
Application of the recommended rate of N via the three sources of N ( inorganic + organic + bioforms) was very effective in improving quality of the fruits in terms of increasing fruit weight and dimensions, total soluble solids, total and reducing sugars and vitamin C content and decreasing fruit peel weight and thickness and total acidity compared to using N completely via inorganic source only.
Fruit peel weight and thickness were tended to increase sharply with decreasing the percentage of inorganic form from 50 to 25% with the application of 37.5% from organic and 37.5% from bio fertilizer. The promotion on fruit quality was associated with decreasing percentages of inorganic form and at the same time increasing percentages of organic and biofertilizers.
The best results with regard to fruit quality were obtained when the trees received N as 25% slow release N fertilizer plus 37.5% organic fertilizer + 37.5% biofertilizer Nitrogen management had no effect on fruit shape value.
Conclusion:
It is suggested to fertilize Balady mandarin trees with N at 1000g / tree as 50% slow release N fertilizer, 25% organic fertilizer + 25% biofertilizer for obtaining an economical yield and improving fruit quality. Application of such promising treatment (1.25 kg Enciabene, 11.63 kg compost El- Neel + 250 g Biogen ) gave net profit over the check treatment (100% fast release N) reached 10953 and 12500 Egyptian pounds in both seasons, respectively as shown in the following table ( feddan =330 trees).
Recommended treatment 2005 2006
Costs of Hort. Practices (pounds) 4000 4500
Costs of the recommended treatment(pounds) 3647 4000
Total costs ( Pounds) 7647 8500
Total Fed. ( ton fruits) 25 26.4
Price of Yioeld ( pounds) 25000 26400
Profit / fed (Pounds) 17353 17900
Check treatment 2005 2006
Costs of Hort. Practices( pounds) 4000 4500
Costs of check treatment( pounds) 800 1000
Total costs ( pounds) 4800 5500
Yield / fed (ton fruits) 11.2 10.9
Price / yield ( pounds) 11200 10900
Profit / fed( pounds) 6400 5400
Net profit over the check treatment 10953 12500
Price of one ton Balady mandarin fruits was 1000 Egyptian pounds in both seasons.