الفهرس 
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Abstract
This study was conducted at the Agricultural Research Station, Faculty of
Agriculture, Alexandria University, during the summer seasons of 2016 and 2017. The aim
of this research was to study the effects of rates and dates of potassium application on
productivity and fiber quality of Giza 86 cotton variety.
The experimental design was split-split plot with four replicates. The three
application dates (1 MAS, 2 MAS and 3 MAS) occupied the main plots, while the three
application rates (zero, 57 and 114 kg K2O/ ha) were assigned to the sub plots.
Measured characters:
A- Vegetative characters
That group included three characters, i.e., plant height, number of vegetative
branches/ plant and number of fruiting branches/ plant.
B- Yield and yield components
That group included nine characters, i.e., number of bolls/plant, number of opened
bolls/ plant, average boll weight (g), seed cotton yield/plant (g), lint cotton yield/ plant (g),
seed cotton yield (kg/ ha), lint cotton yield (kg/ ha), lint percent, seed index.
C- Fiber quality characters:
That group included eight characters, i.e., micronaire reading, maturity index (%),
Upper Half Mean Length(mm) uniformity index (%), strength (g/tex), elongation (%),
reflectance degree (%) and yellowness degree(+b)
The most important results obtained from the present investigation could be summarized as
follows:
A- Vegetative characters
1- Plant height: was insignificantly affected by application date in the two studied
seasons (2016 and 2017) while the effects of potassium rate and the interaction
between (application date * potassium rate) were highly significant in 2016 season
only. The means illustrated that addition of potassium with 57 or 114 kg K2O/ ha
after 1 MAS or 2 months gave the tallest plants, while after 3 months gave the
shortest plants.
2- Number of vegetative branches/ plants: was insignificantly affected by
application date, in 2016 and 2017. However, the effect of potassium rate and its
interaction with application date were significant in 2017 season. The highest rate
of potassium (114 kg K2O/ ha) was the significantly lowest in this trait, with all
three application dates.
3- Number of fruiting branches/ plant: was significantly affected by both
application dates and potassium rates in 2016 and 2017 seasons. The interaction
between the two studied factors was also significant in the two seasons. The
application of potassium with 114 kg K2O/ ha after 2 MAS in 2016 and 1 MAS in
2017 had the significantly highest number of fruiting branches/ plant (14.86 and
14.17, respectively), while no addition of potassium (zero kg K2O/ ha) gave the
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lowest values of this trait were obtained with zero K2O and 1 MAS in 2016 (9.13),
and zero K2O with 1 and 2 MAS in 2017 (10.27 and 10.36, respectively).
B- Yield and yield components
1- Number of bolls/ plant: was significantly affected by the application dates during
the 2016 and 2017 season, as well as the effect of potassium rates in the 2016
season, while the effect in 2017 was highly significant as was the interaction effect
between the studied factors during the 2016 and 2017 seasons. The plants treated
with potassium rate of 114 kg K2O/ ha at the third date (22.42 bolls/ plant) were the
significantly highest, while the lowest number of bolls/ plant was obtained from
plants that were not treated with potassium at first date (17.13 bolls/ plant) in the
2016 season. In the 2017, the plants with the highest significant number of bolls
were the plants treated with high potassium rate (114 kg K2O/ ha) applied at first
date (23.64 bolls/ plant), while the plants that were not treated with potassium (zero
K2O) at the first date (1 MAS) were the significantly least with an average of 19.56
bolls/ plant.
2- Number of opened bolls/plant: was highly significant and significant affected by
application dates during the 2016 and 2017 seasons, respectively, as well as the
effect of potassium rates which was significant and highly significant in 2016 and
2017, respectively. As for the interaction between the studied factors, it had highly
significant effects during the two studied seasons. The plants treated with the
highest rate of potassium (114 kg K2O/ ha) after three months of sowing were
significantly higher in number of opened bolls/ plant (19.66 opened bolls) in 2016,
while, in 2017 season, the same rate applied after 1 MAS was superior in number
of opened bolls/ plant (22.0). Plants not treated with potassium were the least
significant with an average of 11.17 and 15.14 opened bolls in 2016 and 2017,
respectively.
3- Average boll weight: was highly significant affected by application dates was in
the first season (2016) only, while the effect of potassium rates was significant in
both seasons, and the interaction effect between the dates of application and
potassium rates was highly significant in the two seasons. The addition of the high
rate of 114 kg K2O/ ha after three MAS gave the highest average boll weight of 2.3
g in the 2016 season, while in the 2017 season, the addition of the high potassium
rate, whether after 3 MAS or 2 MAS gave the highest significant average boll
weight (2.53 and 2.48 g) with non-significant differences with adding 57 kg K2O/
ha after 3 MAS (2.49 g). The least significant mean of this trait was found in both
seasons (1.82 and 2.02 g), with no potassium addition after 1 MAS, respectively.
4- Seed cotton yield/ plant: was highly significant affected by application dates in
2016 and significant in 2017, while, the effect of the potassium rates was
significant in 2016 and highly significant in 2017, and the interaction effect was
highly significant in both seasons. The high rate of potassium (114 kg K2O/ ha) was
significantly superior when added after 3 MAS, with an average of (45.21 g) in
2016. In 2017 season, the same rate was significantly superior, but when added
after 1 MAS with an average of 53.68 g, while the plants that were not treated with
potassium after 1 MAS had the lowest significant mean in both seasons.
5- Lint cotton yield/ plant was significantly affected by application date, potassium
rates and their interaction in the two seasons of the study. The addition of
potassium with a rate of 114 kg K2O/ ha at the 3 MAS in 2016 season and at the 1
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MAS in 2017 season gave significantly higher lint yield/ plant with an average of
15.5. and 18.15 g, respectively, with insignificant differences with each of 114 kg
K2O/ ha at 3 MAS or 57 kg K2O/ ha at 3 MAS in the 2017, season only. As for the
least significant mean in both seasons, it was with no potassium addition (zero
K2O) at 1 MAS (6.74 and 10.09 g) in 2016 and 2017, respectively.
6- Seed cotton yield/ ha: was significantly affected by application dates in both
seasons, and the effect of the rate of potassium and the interaction between the two
factors were highly significant in 2016 and 2017. The addition of high rate of
potassium (114 kg K2O/ ha) in the third date had the significantly highest seed
cotton yield/ ha in both seasons (3798.53 and 3841.97 kg) in 2016 and 2017. And
the yield of zero potassium first date was the significantly least (1601.14 and
1709.45 kg/ ha) in 2016 and 2017, respectively.