الفهرس 
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Abstract
Two experiments (one of them field experiment and the other
pot experiment ) were carried out at the Experimental Farm of the
Faculty of Environmental Agriculture Science, El- Arish, Suez
Canal University, during the winter seasons of 2009/2010 and
2010/2011. The first experiment aimed to study the effect of three
nitrogen sources (ammonium nitrate 33.5% N, urea 46 N % and
ammonium sulfate 20.6 %N beside control ) and two nitrification
inhibitors (thiourea and DCD) on kohlrabi crop. At 60 days from
planting, plant sample were randomly taken to determine plant
growth parameters and yield as well as at harvest, sample of stems
were taken to determine the content of nitrate and nitrite. The
second experiment was done on lettuce plant and aimed to study
the effect of three nitrogen sources (ammonium nitrate, urea and
ammonium sulfate) and two nitrification inhibitors (thiourea and
DCD), vegetative growth, yield and heads content of nitrate and
nitrite. The experimental design was split-plot in a randomized
complete blokes (RCBD) With three replication for the two
experiments.
FIRST EXPERIMENT:
EFFECT OF NITROGEN FERTILIZER
SOURCES AND NITRIFICATION INHIBITORS ON GROWTH, YIELD AND
NITRATE CONTENT OF KOHLRABI PLANT (Brassica oleracea var gongylodes).
The obtained results could be summarized as follows:
1. Vegetative growth characters and average stem weight
SUMMARY and CONCLUSION
1.1. Effect of nitrogen fertilizer sources:
Application of urea gave the highest values of vegetative
growth characters such as plant highest, root length, root fresh
weight and leaves number/plant compared to control treatment in
the both growing season. Also urea treatment gave the highest
values of stem length, stem diameter, stem weight and average
stem weight comparing to control treatment in the both seasons.
1.2. Effect of nitrification inhibitors
Using DCD nitrification inhibitors gave the highest values of
vegetative growth characters such as plant highest, root length,
root fresh weight and number of leaves/plant comparing to control
treatment in the both seasons. Also DCD treatment gave the
highest mean values of stem length, stem diameter, and stem
weight and average stem weight comparing to control treatment in
the both seasons.
1.3. Effect of interaction:
The interaction between urea and DCD gave the highest
values of vegetative growth characters such as plant highest, root
length, root fresh weight and number of leaves /plant in
comparison with control treatment and the other interaction
treatments in the both seasons. In addition urea combined with
DCD gave the highest values of stem length, stem diameter, stem
weight and average stem weight comparing to control and other
interaction treatments in the both seasons.
SUMMARY and CONCLUSION
2. Dry weight:
2.1. Effect of nitrogen fertilizer sources:
Fertilizing kohlrabi plant with urea gave the highest values
of dry weight such as root dry weight, leaves dry weight and stem
dry weight compared to control treatment.
2.2. Effect of nitrification inhibitors:
Application of DCD gave the highest mean values of dry
weight such as root dry weight, leaves dry weight and stem dry
weight comparing to untreated control.
2.3. Effect of interaction:
Addition of urea combined with DCD was the best interaction
gave the highest values of dry weight such as root dry weight,
leaves dry weight and stem dry weight compared to control
treatment in the two studied seasons.
3. Photosynthesis pigments
3.1. Effect of nitrogen fertilizer sources:
Urea treatment gave the highest chlorophyll a content
comparing to control treatment in the first season, but ammonium
nitrate treatment gave the highest content comparing to control
treatment in the second one. Regarding chlorophyll b, ammonium
sulfate treatment gave the highest values comparing to control
treatment, while urea treatment gave the highest content of total
chlorophyll (a+b) comparing to control treatment in the both
seasons. In addition, carotenoids ammonium sulfate treatment
SUMMARY and CONCLUSION
gave the highest carotenoids content in kohlrabi leaves comparing
to control treatment in the both seasons.
3.2.Effect of nitrification inhibitors:
Application of DCD as nitrification inhibitors gave the
highest content of chlorophyll a, chlorophyll B, chlorophyll a+b
and carotenoids compared to untreated control in the two tested
seasons.
3.3.Effect of interaction:
The interaction between ammonium nitrate and DCD gave
the highest values of chlorophyll a, b and carotenoids content
comparing to control treatment in the both seasons of study. On
the other hand the interaction between urea and DCD gave the
highest content of total chlorophyll a+b compared to control
treatment in the both seasons.
4. Yield quality
4.1. Effect of nitrogen sources:
Fertilizing kohlrabi plant with ammonuim nitrate gave the
highest values of T.S.S of leaves in first season compared to the
other nitrogen sources, while control treatment gave the highest
content in the second one. In addition, application of urea gave
the highest NO3 and NO2 contents in both seasons comparing to
control treatment which gave the lowest values in this respect. On
the other hand carbohydrates contents was not significantly
SUMMARY and CONCLUSION
affected by all studied nitrogen sources in the both seasons of
study.
4.2. Effect of nitrification inhibitors:
T.S.S and carbohydrate contents in kohlarbi leaves were not
significantly affected by all tested nitrification inhibitors in the
both seasons, while control treatment gave the highest content of
NO3 and NO2 compared to DCD as NIs treatment in the both
seasons.
4.3. Effect of interaction:
The interaction between ammonuim nitrate without
nitrification inhibitors gave the highest values of T.SS in first
season, while all interactions treatments between control, nitrogen
fertilizer and nitrification inhibitors gave the highest values in
second season. While, the interaction between urea treatments
without nitrification inhibitors gave the heights values of NO3 and
NO2 and control treatment recorded the lowest values in this
respect in both seasons of study. In addition, carbohydrate
contents did not show any significant differences, except the
interaction between urea and thiourea and the interaction between
ammonuim nitrate with DCD or without nitrification inhibitors in
the second season.
SUMMARY and CONCLUSION
SECOND
EXPERIMENT:
EFFECT
OF
NITROGEN
FERTILIZER SOURCES AND NITRIFICATION INHIBITORS ON
GROWTH, YIELD AND NITRATE CONTENT OF LETTUCE PLANT
(Lactuca sativa var. capitata )
The obtained results could be summarized as follows:
1. Vegetative character and average head weight
1.1. Effect of nitrogen fertilizer sources:
Urea fertilizers treatment gave the highest values of
vegetative growth characters such as plant height, root length,
fresh weight of root and leaves and number of leaves/plant
comparing to unfertilized control treatment in the both seasons,
also adding urea to lettuce plant gave the highest head height,
head
diameter, average head weight, and yield per fed. on comparing
control treatment in the both seasons.
2.1. Effect of nitrification inhibitors:
Application of thiourea as nitrification inhibitors to lettuce
plant gave the highest values of vegetative growth character such
as plant height, root length, fresh weight root and leaves and
number of leaves/plant comparing to control treatment in the both
seasons. In addition, DCD treatment gave the highest head height,
head diameter, average head weight, and total yield comparing to
control treatment in the both seasons.
SUMMARY and CONCLUSION
3.1.Effect of interaction:
The interaction between urea and thiourea gave the highest
values of vegetative growth character such as plant height, root
length, fresh weight root and leaves and number of leaves/plant
comparing to control treatment in the both seasons. Also urea
combined with DCD was the best interaction treatment which
gave the highest values of head height, head diameter, average
head weight, and
total yield per fed. comparing to control
treatment (control N X control NIs ) in the both seasons.
2. Dry weight
2.1. Effect of nitrogen fertilizer sources:
Fertilizing lettuce plant with urea gave the highest values
of dry weight such as root dry weight, leaves dry weight and stem
dry weight in comparison with un fertilized control in the both
seasons.
2.2. Effect of nitrification inhibitors:
Nitrification inhibitors as DCD treatment gave the highest
values of dry weight of different plant parts, i.e., root dry weight,
leaves dry weight and stem dry weight of lettuce plant compared
to control treatment in the both seasons.
2.3.Effect of interaction:
Urea combined with DCD treatment gave the highest values of
lettuce plant dry weight as root, stem and leaves/plant comparing
to control treatment in the both seasons of study.
SUMMARY and CONCLUSION
3. Photosynthesis pigments
3.1.Effect of nitrogen fertilizer sources:
Using urea as nitrogen sources gave the highest content of
chlorophyll a,b, total chlorophyll (a+b) and carotenoids comparing
to control treatment in the both seasons, except chlorophyll a
which did not reach the S% level of significance.
3.2.Effect of nitrification inhibitors:
Application of thiourea to lettuce plant gave the highest
content on chlorophyll a and chlorophyll a+b in leaf tissues of
lettuce plant comparing to control treatment in two seasons, but
DCD treatment gave the highest chlorophyll b and carotenoids
comparing to control treatment in the both seasons of study.
3.3. Effect of interaction:
Fertilizing lettuce plant with urea combined with thiorurea
was gave the most favorable interaction treatment for increasing
the contents of chlorophyll a, chlorophyll b, chlorophyll a+b and
carotenoids in lettuce leaves comparing to control treatment in the
two seasons.
4. Yield quality
4. 1. Effect of nitrogen fertilizer sources:
Nitrogen source was not significantly affected TSS% in
lettuce leaves in the first season, while ammonium sulfat treatment
gave the highest TSS values in the second one. On the other hand,
SUMMARY and CONCLUSION
urea treatment gave the highest NO3 and NO2 content in the both
seasons comparing to control treatment which gave the lowest
values in this respect. While, all nitrogen sources did not show
any significant effect regarding carbohydrates content in lettuce
heads.
4.2. Effect of nitrification inhibitors:
No significant effect was dectected due to nitrification on
TSS% and carbohydrate content of lettuce heads in the two tested
seasons, while, NO3 and
NO2 was at its minimum values when lettuce plant treated with
thiourea compared to untreated plants with nitrification inhibitors.
4.3. Effect of interaction:
The interaction between all nitrogen sources combined with
nitrification inhibitors gave the heights values of TSS%. Also the
interaction between urea without nitrification inhibitors gave the
heights values of NO3 and NO2 while control treatment gave the
lowest values of NO3 and NO2 in the lettuce heads in both seasons
of study. No significant differences were found among all the
interaction treatments regarding carbohydrate content, except the
interaction between urea with DCD or thiourea which increased
the content of total carbohydrates in the first and second seasons,
respectively.
771
SUMMARY and CONCLUSION
CONCLUSION
Under similar condition of this experiment. It could be
concluded that, kohlrabi and lettuce plants fertilized with urea
combined and DCD or thiourea being the most effective and
favorable interaction treatments on increasing vegetative growth
traits, dry weight of differente plant parts. Also these treatments
increased average head weight and total yield per feddan in lettuce
in both seasons.
Application of thiourea or DCD combined with control
(nitrogen source) followed by ammonium sulfate or ammonium
nitrate combined with thiourea or DCD were the recommended
interaction treatments that did not lead to excessive nitrate and
nitrite contents in edible portions of kohlrabi and lettuce plant