الفهرس 
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Abstract
SUMMARY
Strawberry plants as affected by N fertilization at variable
rates without or with nitropyrin compination at different doses
was the aim of this investigation. Cold stored seedlings of ”Sequoia”
(Frigo plants) were used in these experiments.
Incubation experiment (or studying nitrapyrin persistence and
degradation in soil as influenced by physical, chemical and bacteriological
action has been executed in small vials at room temperature
for four months,
Pot experiment in the greenhouse at the Strawberry Center
in the Faculty of Agriculture-Am Shams University and further
field experiments at the Southern Sector of El-Tahreer Province
were also carried out. hi the pot experiment, ammonium sulphate
as a source of nitrogen was applied at 100, 1 SO and 200 kg N/Feddan
without or with nitrapyrin at 0.5 and 1.0 lb/Feddan. In the field
experiment, nitropyrin was only applied at 0.5 lb/Feddan. Results
could be summarized individually as follows:
A) Incubation uperiment:
* Nitrapyrin in the 15 day periodically aerated system at concentrations
ranging from 0.4 to 1.6 ppm resulted in less than 1096
conversion of ammonia into nitrate when incubated with soil at room
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temperature for four months. The control and lower concentrations
of nitrapyrin, however, revealed rapid consumption of
ammonia through the first ten weeks.
* Reinfestation in the 15 day periodically aerated system increased
the nitrification process in soil resulting in complete conversion
of ammonia into nitrate within four months of incubation even
at the highest concentration of nitrapyrin.
* Nitrification took place rapidly in the open incubation system
as a result of rapid volatilization of nitrapyrin.
B) The pot and field experiments:
1. Ph)lsical and chemical characteristics o( (nzits:
oj Firrrrness:
* Strawberry f”.tits exhibited a gradual decrease in firmness
with harvesting time towards the end of the season.
* Increasing N fertilization doses resulted in an apparent decrease
in firmness.
* Nitrapyrin at different doses in combination with N fertilizers
decreased fruit firmness except for treatments with high rates
of nitrogen (200 kglFeddan) where fruits were suffering from
deformation.
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*
b) Fruit weight:
Harvesting time had an apparent effect on average fruit weight.
Fruits were relatively large at the middle of harvesting season.
Small fruits, however, were usually observed at the begining
and end of the season.
* Increasing N fertilization doses increased the average [ruit
weight.
* Nitrapyrin at a rate of 0.5 lb/Feddan in combination with 100
and 150 kg N/Feddan gave an apparent increase in average
fruit weight. Higher dose of nitrapyrin with different N fertilization
treatments showed either no or even negative effects,
sometimes concomitant with severe deformation in fruit shape.
*
c) TSS4Jf.
Total soluble solids percentage revealed an apparent DROP in
the middle of the season corresponding to the maximum average
fruit weight values. High doses of N fertilization showed a
relative increase in TS596.
* Nitrapyrin at a rote of 0.5 or 1 Ib/Feddan, was fOlmd to increase
the T5S96 for the 100 N and 150 N treatments specially at
the early harvesting stages. No marked increase llIClS observed
for the 200 N treatment.
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••
dJ Total acidity, pH value, augurs and ascorbic acid:
No relationships could be realized from the data of total acidity,
pH, sugars and ascorbic acid contents as affected by the different
N fertilization treatments with or without nitrapyrin.
2. CrOp pnxtuction of the pot uperiment:
a} Fertilization treatments with 100 kg N/FeddDn:
•• Nitrapyrin was foUTtd to increase plant growth as confirmed
from the dry weight of plants at the end of the harvesting
season. The crop production exhibited an apparent increase
by using nitrapyrin at 0.5 lb/Feddan while the higher dose rsulted
in, lower fruit yields.
b) Fertilization treatments with 150 leg N/Feddan:
•• Increasing the N fertilization dose from 100 to 150 kg/Feddan
revealed a corresponding increase in both crop production and
plant growth •
•• Nitrapyrin at a rate of 0.5 lb/Feddan increased both crop production
and dry matter weight of plants.
* Increasing the nitrapyrin dose to 1 lb/Feddan resulted in stunting
of plants with a striking DROP in the crop production.
••
c) Fertilization treatments with 200 Jql N/Feddan:
Although an apparent increase in growth was observed with
200 kg N/Feddan, no marked increase in crop production occurred.
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Nitrapyrin at both concentration rates (0.5 and 1 lb/Feddan)
caused severe sttBlting of plants with a marked DROP in crop
production.
* Generally, fertilization at 150 kg N/Feddan in combination
with nitrapyrin at a rate of 0.5 lb/Feddan gave the best results
for crop production.
3. Crop production of the field uperimertt:
* Nitrapyrin at a rate of 0.5 lb/Feddan had a positive effect
on both plant growth and fruit production exhibiting an increase
of about 98 and 10% for the 100 N treat ment and 29 and 31%
for the 150 one, respectively. The same dose of nitrapyrin,
however, had a negative effect on lx>th growth and crop production
when combined with the 200 N treatment.
* Generally, application of nitrapyrin at a rate of 0.5 lb/Feddan
in combination ””ith 150 kg N/Feddan was economically and
commercially the best of all fertilization treatments. 1l allowed
continuous high yield production of fn.dts of quite good quality
throughout the season.