الفهرس 
Effect of nitrogen fertilization ratesOnly 14 pages are availabe for public view
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Abstract
This study was conducted at a private farm in Abo Ghalib, Giza
Governorate, Egypt, during the two successive seasons of 2015 and 2016.
The aim of this study was to determine the optimal requirements of
nitrogen and phosphorus fertilizations for Festival strawberry cultivar
nurseries, since it is an important cultivar which planted widely in Egypt
for exportation as fresh or frozen fruits.
Nursery mother transplants of strawberry cv. Festival (Super Elite
plants) were taken out from the cold storage then dipped in 0.2%
Rhizolex solution for 20 minutes and planted as plugs on the 1st and 4th
of May in the first and second season, respectively. The transplants were
spaced at 1.5 m between plants and 1.75 m between rows. Flowers were
continuously removed from mother plants during the first month after
transplanting. Drip irrigation system in the first two months was used then
the micro sprinkler irrigation system (4 m x 5 m) was used.
Four nitrogen fertilization rates (83, 100, 117 or 134 kg N/feddan)
were added as ammonium nitrate fertilizer, while commercial phosphoric
acid at rates of 0, 40, 60, 80 or 100 l/feddan to make five phosphorus
fertilization rates (38, 62, 74, 86 or 98 kg P2O5/feddan) were used. A
constant rate of potassium sulfate (96 kg K2O/feddan) was added. The
fertilizers were added through the drip-irrigation system three times a
week during the nursery period.
The experiment was a factorial designed as randomized complete
blocks with three replicates. Each experimental plot contained two rows
each of 1.75 m wide and 5 m long (plot area = 17.5 m2).
On 1st of October, number of main runners/mother plant and
number of marketable daughter transplants/m2 were recorded. Vegetative
growth characteristics (root and plant lengths, number of leaves/plant average leaf area and fresh and dry weights of root and vegetative
growth), SPAD readings, total soluble phenol content in leaves, leaf
relative water content, leaf membrane stability index of the obtained
transplants were also recorded. In addition, crown diameter and crown
carbohydrate were determined. Moreover, leaf mineral content was
analyzed.
The obtained results could be summarized as follows:
Effect of nitrogen fertilization rates
1- The obtained results revealed that the applications of 117 or 134 kg
N/feddan gave the highest significant number of main runners/mother
plant, number of marketable transplants/m2
, all recorded vegetative
growth parameters (root and plant lengths, number of leaves/plant,
average leaf area and fresh and dry weights of roots and vegetative
growth), SPAD readings, crown diameter and crown carbohydrates
content, and percentages of nitrogen, phosphorus, potassium and
magnesium in leaves in both growing seasons. On the contrary, the
application of 83 Kg N/feddan gave the lowest significant ones.
2- Nitrogen fertilization exhibited an inverse effect on leaf total soluble
phenols and leaf membrane stability index. The obtained results
revealed that both parameters were decreased as the nitrogen
fertilization increased. On the other hand, nitrogen fertilization
didn’t significantly affect the leaf relative water content and calcium
percentage in leaves.
Effect of phosphorus fertilization rates
1- The applications of 86 or 98 kg P2O5/feddan gave the highest
significant numbers of main runners and marketable transplants, and
growth parameters while the application of 38 kg P2O5/feddan gave
the lowest ones in both seasons.2- The applications of 86 or 98 kg P2O5/feddan gave the highest
significant SPAD readings in the first season, while the phosphorus
fertilization did not affect significantly the SPAD readings in the
second season.
3- As the phosphorus rates increased, total soluble phenols in strawberry
leaves decreased. However, the differences were not significant in
both seasons.
4- Increasing the phosphorus rates from 38 to 98 kg P2O5/feddan
resulted in increases in relative water content and membrane stability
of strawberry leaves in both seasons. However, the differences were
not significant for both parameters in both growing seasons.
5- The highest rate of phosphorus (98 kg P2O5/feddan) gave the highest
values of crown diameters in both growing seasons, while the high
rates of phosphorus applications (74, 86 or 98 kg P2O5/feddan) gave
the highest values of crown carbohydrates without significant
differences among them. On the other hand, the lowest rate of
phosphorus application (38 kg P2O5/feddan) gave the lowest values
of both characteristics in both seasons.
6- The 86 and 98 kg P2O5/feddan application gave the highest
percentages of nitrogen, phosphorus, potassium, calcium and
magnesium in both seasons, while the 38 and 62 kg P2O5/feddan
application gave the lowest percentages of nitrogen, phosphorus,
potassium, calcium and magnesium in both seasons.
Effect of nitrogen and phosphorus fertilization interactions
1- The interactive effects of the applications of nitrogen and phosphorus
fertilizations were non-significant on the number of main
runners/mother plant, all growth parameters, SPAD readings, total
soluble phenols in leaves, leaf relative water content and membrane stability index, and percentages of phosphorus, potassium, calcium
and magnesium in leaves in both growing seasons, indicating that
both factors acted independently for these characters.
2- High rates of nitrogen with high rates of phosphorus fertilizations
exhibited significant increases in number of marketable
transplants/m2, and nitrogen percentage in leaves. The applications of
117 kg N with 86 or 98 kg P2O5/feddan, and 134 kg N with 74, 86 or
98 kg P2O5/ feddan were the most effective applications.
3- The interactive effects of nitrogen and phosphorus fertilizations were
not significant on crown diameter in the first season and crown
carbohydrates in both seasons, the applications of 117 or 134 kg N/
feddan with 98 kg P2O5/ feddan gave the highest values in both
seasons.