الفهرس 
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Abstract
Two field experiments were conducted at the Agricultural Experimental Center, Faculty of Agriculture at Moshtohor during winter seasons of 1993/1994 and 1994/1995. The study aimed to
investigate the effect of five planting dates within four fertilization
levels on the yield and quality of two cultivars of lettuce.
Split-split plot design was used where the five monthly planting dates (between October, 1st to February, 1st) were arranged in th main plots. the two cultivars (Balady and Dark Green) were
arranged in subplots and the four co~pound fertilizer levels (10kg N+
20 kg P20S + 10 kg K20, 20 kg N + 40 kg P205 + 20 K20, 40 kg N + 60 P205 + 40 kg K20, and 80 kg N + 80 kg P20S + 80 kg
K20/fad.) were arranged in the sub-subplots. The data taken were
on plant vegetative growth at marketable stage, chemical
constituents of plant leaves, total yield and quality. Results revealed
the following:
1. Vegetative growth characteristics:
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1. The highest plants were associated with earliest planting
date (October, 1st) and delaying transplanting date significantly
decreased plant height. Transplanting in December or January
tended to show low plant height Balady cultivar was taller than
Dark Green cv. and the differences were highly significiant. The
effect of fertilization level on plant height was not great (about
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10%), however as the level of fertilizer increased as the plant height
increased upto the third level (40 kg N + 60 kg P205 + 40 kg
K20/fad. Interactional effects did not show any significant
differences except that for planting date within cultivars. In general,
such interactions followed nearly similar trend to that of the main
effects.
2. Plants fresh weight tended to increase by delaying
transplanting date to December, January or February. Comparing
the tested cuItivars, it was found that Dark Green cv. preceded
Balady cv. Plant fresh weight positively responded to the increase
in fertilization level upto the third level. Th~;general trend of
interactional effects may indicate that fertilization level is the most
important factor then comes planting date.
3. Plants dry weight was the highest at December and January
planting dates. Dark Green cv. showed higher plant dry weight than
Balady cv. Plants dry weight gradually and significantly increased
with increasing the level of fertilization upto the third level (L3),
increasing fertilizer level upto IA had a decrement effect on plant
dry weight. Interactional effects showed some differences, and
indicated that plant dry weight showed more response to fertilization
at the earliest planting date (October, 1st) than at the later one
(January, 1st).