الفهرس 
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Abstract
This study was conducted in a private farm at EI-Baliana district, Sohag Gvemorate, Upper Egypt, during 1991/92 nnd 1992/93 seasons to study the effect of plant spacing and the response of onion (Allium cepa L.) cultivar ”Giza 6” plants to fertilization with different rates of nitrogen and potassium under the location of the experiment conditions.
The obtained results could be summarized as follows:
1- Plant height:
- Plant height was slightly increased by increasing plant spacing in the two seasons.
- Nitrogen and potassium, as will as all the interaction between the studied fa.ctors were of insignificant efiect on this character.
2- Number of leaves/plant:
- The highest values [or tIus character were obtained by wide spacing (7.5 em).
Varying the applied rates of nitrogen and potassium was of insignificant effect on this character.
- No significant effect could be detected due to any of the possible interactions between the studied factors
3- Neck (pseudostem) diameter:
- Increasing plant spacing significantly increased neck diameter in both seasons.
- The highest rate of nitrogen (70 kg N/fed.) resulted in significant increase in the values of this character
- The highest values for this character was obtained when the plants received potassium at the highest rate (150 kg K20/fed).
- All interactions were of insignificant eifect on this character.
- Plant spacing was the only effective factor on this trait, since the wide spacing resulted in an increase in the values of this character compared with close spacing.
- Nitrogen, potassium and all interactions failed to show significant effect on this trait in the two seasons.
5- Bulbing ratio:
- Bulbing ratio was significantly increased by wider plant spacing in the two experimental seasons.
- lhe values of this character was significantly inreased by increasing the applied rate of nitrogen and potassium, but in the second season onl
- Nitrogen, potassium and all interactions failed to show significant effect on this trait in the two seasons.
6- Yield of double bulbs:
Production of double bulbs increased by wide plant spacmg, however, neither of the three studied [actors nor the interaction
between them could show significaIlt effect on this ChArActer, except increasing the applied rate of potassiwn, which increased the yield of double bulbs in the first season.
7- Weight of bolting bulbs:
- Production of bolting bulbs increased by wider spacing.
- Increasing the applied rate of potAssium significantly increased the
production of bolting bulbs in the first season only.
- Neither varying the applied rate of nitrogen nor all possible interactions between the studied factors could show significant effect on this trait.
8- Local marketable yield of bulb (I!er fcdda!!h
- Plant spacing, in the second season, and potassium fertilization, in the first one, significantly affected this trait.
- No significant effect could be detected due to varying the applied rate of nitrogen or any of the interactions between the studied factors in the two seasons.
9- Exportable yield:
- Close spacing (5 cm) treatment resulted in an increase of 26.440/0 and 21.500/0 in the exportable yield over the wide spacing one in the first and second seasos, respectively.
- Potassium affected the values of this character in the first season only.