الفهرس 
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Abstract
The present investigation was carried out during the course of three successive 2004, 2005 and 2006 seasons on 45 fruitful Balady mandarin trees grown in a private orchard situated at Derwa village, Mallawi district, Minia Governorate. The selected trees were 18 year old budded on sour orange rootstock and planted in sandy soil at 3.5 x 3.5 m. distance. The soil is well drained and with a water table depth not less than two meters.
Fourty – five Balady mandarin trees were devoted for achieving this experiment. Such trees were carefully selected as being healthy as well as nearly uniform in both vigour and size.
The objective of this investigation was adjusting the best ratio of inorganic, organic and bioforms of N that responsible for obtaining good yield and improving fruit quality of Balady mandarin trees.
This experiment consisted from the following fifteen treatments from different ratios of inorgani, organic and bioforms of N :
1- Using the recommended rate of N ( R.R.) i.e. 1000 g N/ tree completely via mineral source (2.99 kg ammonium nitrate/ tree).
2-Using R.R. of N as 90% mineral ( 2.69 kg ammonium nitrate / tree) + 10 % organic ( 40 kg F.Y.M./ tree).
3-Using R.R. of N as 90% mineral ( 2.69 kg ammonium nitrate / tree) + 5 % organic ( 20 kg F.Y.M./ tree) + 5% bio ( 50 g Biogen / tree).
4-Using R.R. of N as 80% mineral ( 2.39 kg ammonium nitrate/ tree) + 20% organic ( 80 kg F.Y.M./ tree).
5-Using R.R. of N as 80% mineral ( 2.39 kg ammonium nitrate/ tree) + 10% organic ( 40 kg F.Y.M./ tree) + 10 % bio ( 100g Biogen/ tree).
6- Using R.R. of N as 70% mineral ( 2.09 kg ammonium nitrate/ tree) + 30% organic ( 120 kg F.Y.M./ tree).
7- Using R.R. of N as 70% mineral ( 2.09 kg ammonium nitrate/ tree) + 15% organic ( 60 kg F.Y.M./ tree). + 15 % bio ( 150 g Biogen / tree).
8-Using R.R. of N as 60% mineral ( 1.79 kg ammonium nitrate/ tree) + 40% organic ( 160 kg F.Y.M./ tree).
9- Using R.R. of N as 60% mineral ( 1.79 kg ammonium nitrate/ tree) + 20% organic ( 80 kg F.Y.M./ tree) + 20 % bio ( 200 g Biogen / tree).
10- Using R.R. of N as 50 % mineral ( 1.50 kg ammonium nitrate/ tree) + 50 % organic ( 200 kg F.Y.M./ tree).
11- Using R.R. of N as 50 % mineral ( 1.50 kg ammonium nitrate/ tree) + 25 % organic ( 100 kg F.Y.M./ tree) + 25 bio ( 250 g Biogen / tree).
12- Using R.R. of N as 40 % mineral ( 1.20 kg ammonium nitrate/ tree) + 60 % organic ( 240 kg F.Y.M./ tree).
13- Using R.R. of N as 40 % mineral ( 1.20 kg ammonium nitrate/ tree) + 30 % organic ( 120 kg F.Y.M./ tree) + 30% bio ( 300 g Biogen / tree).
14- Using R.R. of N as 30 % mineral ( 0.90 kg ammonium nitrate/ tree) + 70 % organic ( 280 kg F.Y.M./ tree).
15- Using R.R. of N as 30 % mineral ( 0.90 kg ammonium nitrate/ tree) + 35 % organic ( 140 kg F.Y.M./ tree) + 35% bio ( 350 g Biogen / tree).
Therefore, the experiment included 15 treatments. Each treatment replicated three times, one tree per each. Inorganic, organic, and bioforms of N were applied in the sources of ammonium nitrate ( 33.5 % N ) , farmyard manure ( F.Y.M.) (0.25 % N , 1.2 % K2O, 0.8 % P2O5 ) and Biogen, respectively. Ammonium nitrate was splitted into four equal batches and applied on the first week of March, May, July and September. Farmyard manure at the prementioned amounts was added once in the first week of January. Biogen was added once in the first week of March. All the selected trees (45 trees) received N at fixed rate i.e. 1000 g N / tree.
The present experiment was set up in completely randomized block design.
For evaluating the effect of the different ratios between inorganic, organic and bioforms of N fertilization on growth, nutritional status of the trees, yield and fruit quality of Balady mandarin trees, the following measurements were recorded:
1-Leaf area in the Spring growth cycle (cm2)
2-Plant pigments in the fresh leaf (chlorophylls a, b, total chlorophylls and total carotenoids ( mg/ g F./W.)
3-Percentages of N, P and K in the leaves of non- fruiting Spring shoots.
4-Percentages of Initial fruit setting and fruit retention
5-Percentages of June drop and preharvest fruit drop
6-Yield expressed in weight (kg.) and number of fruits / tree.
7-Physical fruit characters namely (weight (g.), height and diameter of fruits (cm) as well as , fruit peel weight % and thickness(cm.) ).
8-Chemical fruit characters namely, total soluble solids %, total acidity %, T.S.S. / acid, total sugars %, reducing sugars %, vitamin C (mg/ 100 ml juice) and nitrite content (ppm).
The nearly same obtained results obtained in the three seasons of study could be summarized under the following main items:
1-Leaf area:
Application of the recommended rate of N namely 1000 g N/. tree through 50 – 90 % mineral N (ammonium nitrate), 5- 50 % organic ( F.Y.M.) and 5 to 25 % bioforms (Biogen) was very effective for stimulating the leaf area of Balady mandarin trees compared to using all amounts of N via mineral source only or using mineral N at percentages lower than 50 % with organic and biofertilization.
The stimulation on the leaf area was associated with decreasing percentage of mineral N (ammonium nitrate) from 100 to 70 % and increasing percentages of F.Y.M. from 5 to 30 % and Biogen from 5 to 15 % . Decreasing percentages of mineral N from 50 to 30 % and at the same time increasing percentages of F.Y.M. and Biogen from 50 to 70 % considerably reduced the leaf area. Using mineral N at 100 % out of the recommended rate of N was superior the application of N as 30 to 40 % mineral plus 25 % to 70 % F.Y.M. and 25 to 35 % Biogen in stimulating the leaf area. The minimum values were registered in the trees supplied with N as 30% mineral, and 70 % F.Y.M. Fertilizing the trees with N as 70 % mineral + 15 % F.Y.M. + 15 % Biogen gave the best results.
2-Percentages of N, P and K:
Application of the recommended rate of N ( i.e. 1000 g / tree) via mineral sources at 50 to 90 %, 5- 50 % organic plus 5 to 25 % bioforms considerably was accompanied with enhancing percentage of N in the leaves compared to using N completely via mineral source or using mineral N at percentages lower than 50 % with organic and bioforms of N at 60 to 70 %. The stimulation was associated with decreasing percentages of mineral source from 100 to 50 % and increasing percentage of F.Y.M. and Biogen from 5 to 50 %. However, the percentage of N tended reasonably to reduce with reducing percentage of mineral N from 50 to 30 % and at the same time increasing percentage of the organic and biofertilizer from 60 to 70 %. Application of N through the three sources ( ammonium nitrate, F.Y.M. and Biogen) obviously was followed by enhancing percentages of P and K in the leaves compared to using N via mineral source only (ammonium nitrate). There was a gradual promotion on percentages of P and K in the leaves with decreasing percentages of mineral source from 100 to 30 % and at the same time increasing percentages of F.Y.M. and Biogen from 0.0 to 70 %.
The maximum values of N was recorded on Balady mandarin trees received N as 50% mineral, 25 % F.Y.M. and 25 % Biogen Balady mandarin trees that fertilized with N as 30 % mineral + 35 % F.Y.M. + 35 % Biogen gave the maximum P and K in the leaves.
3-Percentages of initial fruit setting and fruit retention .
Application of N as 50 to 90 % mineral + 5 to 50 % F.Y.M. + 5 to 25 % Biogen reasonably was very effective for improving such two percentages compared to fertilization of N completely via mineral source or using mineral N at percentages lower than 50% with organic and biofertilization. Using mineral source at 30 to 40 % plus Biogen and F.Y.M. at 60 to 70% obviously reduced percentages of initial fruit setting and fruit retention compared to using N completely via mineral source. The stimulation was correlated with decreasing mineral source from 100 to 50 % and increasing F.Y.M. and Biogen from 0.0 to 50 %.
The maximum values were recorded on Balady mandarin trees that received N fertilization as 70 % mineral + 15 % F.Y.M. + 15 % Biogen. Fertilization of the trees with N as 30 % mineral + 70 % F.Y.M. is unfavourable for Balady mandarin trees owing to producing the lowest number of fruits/ tree.
4-Percentages of June and preharvest fruit dropping:
June and Preharvest fruit dropping were materially reduced with using N as 50 to 90 mineral plus 5 to 50 % F.Y.M. and 5 to 25% Biogen compared to using N completely via mineral source or using N at 30 to 40 % mineral plus 60 to 70 % F.Y.M. and Biogen. The reduction was associated with decreasing mineral source percentages from 100 to 70 % and at the same time increasing the percentages of F.Y.M. from 5 to 30 % and Biogen from 5 to 15 %. Fertilizing the trees with N at 1000 g as 70 % mineral + 15 % F.Y.M. plus 15 % Biogen resulted in the minimum values.
The highest values were recorded on the trees received N as 30 % mineral + 70 % F.Y.M.
5-Yield:
In most cases, application of N at the recommended rate as 50 to 90 % mineral plus 5 to 50 % F.Y.M. plus 5 to 25 % Biogen resulted in an obvious promotion on the yield expressed in number of fruits per tree and weight compared to using N completely via mineral source or using mineral N at percentages lower than 50% with organic and biofertilization. There was a great decline on the yield with using percentages of mineral source lower than 50 % and at the same time using F.Y.M. and Biogen at percentages higher than 50 % . The best yield was recorded on trees that received N as 70 % mineral + 15 % F.Y.M. and 15 % Biogen. Application of N completely via mineral source was preferable than using N as 30 to 40 % mineral plus F.Y.M. and Biogen at 60 to 70 % in improving the yield. Fertilizing the trees with N as 30 % mineral + 70 % F.Y.M. resulted in the minimum values.
6-Physical characters of the fruits
Application of N as 50 to 90 % mineral source + 5 to 50 % F.Y.M. + 5 to 25 % Biogen considerably improved fruit weight and dimensions and caused a significant reduction on fruit peel weight and thickness compared to using N completely via mineral source or using mineral N at percentages lower than 50 % with organic and biofertilization. The promotion on fruit weight and dimensions was associated with decreasing percentages of mineral source from 100 to 70 % and at the same time increasing percentages of F.Y.M. from 5 to 50 % and Biogen from 5 to 25 %. There was material reduction on weight and dimensions of fruit and increase in fruit peel weight and thickness with decreasing percentages of mineral source from 50 to 30 % and at the same time increasing percentages of F.Y.M. and Biogen from 50 to 70 %. The highest fruit weight and dimensions was recorded on the trees received N as 70 % mineral source + 15 % F.Y.M. + 15% Biogen. Fertilizing the trees with N at 30 % mineral + 70 % F.Y.M. gave the lowest values.
7-Chremical characters of the fruits:
Application of N as 30 to 90 mineral source + 5 to 70 % F.Y.M. and Biogen at 5 to 35 % obviously was responsible for improving chemical quality of the fruits in terms of increasing total soluble solids, T.S.S. / acid, total and reducing sugars and vitamin C content and in decreasing both total acidity % and nitrite content (ppm) compared to using N completely via mineral source. The promotion on chemical quality of the fruits was associated with decreasing percentages of mineral N from 100 to 30 % and increasing percentages of F.Y.M. from 5 to 70 and Biogen from 5 to 35 % The best results were obtained when the trees were fertilized with N as 30 % mineral source + 35 % F.Y.M. and 35 % Biogen. Application of N completely via mineral source gave unfavourable effects on chemical quality of the fruits .
Conclusion:
It is suggested to application of the recommended rate of N (1000 g / tree) as 70 % inorganic source, ( 2.09 kg ammonium nitrate) 15 % F.Y.M. (60 kg/ tree and 15 % Biogen ( 150 g / tree) for gaining an economical yield and improving fruit quality of Balady mandarin trees growing under sandy soil. Also, Net return gained due to application of such promising treatment reached 3000 , 4000 and 4000 Egyptian pounds per feddan above the treatment involved the application of N via mineral source only in the three seasons, respectively. This promising treatment could alleviate the pollution of fruits with nitrite.
It could be concluded that using bio and organic fertilizers along with inorganic form would achieve a beneficial improvement to the growth vigour of Balady mandarin trees. In addition, it reduces the need for inorganic fertilizers and decreases the costs of production as well as environmental pollution problems.
On the light of the previous results, it can be stated that replacing 30 % of N requirements for Balady mandarin trees by 15 % organic and 15 % biofertilization improved the yield and minimized the production costs and the environmental pollution which could be increased by the excess of chemical N fertilizers.