الفهرس 
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Abstract
Two field experiments were carried out at Zarzora region
during the two seasons of 1997/98 and 1998/99 to study the effect
of pre-summer crops and nitrogen levels on growth, yield and
quality of Elane suqar beet cultivar.
The stUQY included four preceding summer crops (cowpea,
maize. sorghum and sunflower) and four N- levels (0, 30, 60 and 90
Kg N/fad). The results can be summarized as follows:
A- Effect of preceding crog§;
a..Soil properties:
1. Soil porosity percentage was affected by preceding summer
crops. Growing sugar beet after cowpea increased the soil
porosity compared with that after maize, sunflower and sorghum.
2. Total nitrogen content was affected by preceding summer crops.
Total nitrogen increased by growing sugar beet after cowpea in
the soil in the two seasons.
3. Total phosphorus was affected by preceding summer crops.
Cowpea and sorghum increased the phosphorus content of the
soil.
4. Total potassium was not affected by preceding summer crops.
5. Total organic matter content of the soil was affected by preceding
summer crops. Sor:ghum BOO ffi8i~ 89 preeeding crops. - U~
Sorghum and maize as preceding crops increased the organic
matter content of the soil.
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5. Relative Growth Rate (RGR) was significantly affected by
preceding summer crops at both periods, i.e. 100·121 and 121-
142 days from sowing. The RGR value after cowpea and
sorghum was higher than that after maize or sunflower.
c. Root character:
1. Root length was significantly affected by preceding summer
crops in one season. The highest value of root length was
obtained from growing sugar beet after cowpea in the first and
second seasons.
2. Root diameter was significantly affected by preceding crops in
both seasons. The maximum value of root diameter was
recorded when growing sugar beet after cowpea.
3. Root weight was not significantly affected by preceding summer
crops.
d. Yield:
1. Top yield (tons/fad) was not significantly affected by preceding
summer crops in both seasons.
2. Root yield (tons/fad) was significantly affected by preceding
summer crops. Sugar beet preceded by cowpea gave heaviest
root yield (23.0 and 24.50 tonlfad, respectively in both seasons.
3. Biological yield (Tonslfad) was significantly affected by preceding
summer crops in both seasons. It could be concluded that
cowpea is the beSt preceding crop for sugar beet for producing
the highest biological yield. On the other hand, sugar beet
preceded by sorghum produced the lowest biological yield.
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4. Sugar yield (Tons/fad) was significantly affected by preceding
summer crops in both seasons. cowpea as preceding crop for
sugar beet gave the maximum the sugar yield /fad (3.96 and 4.28
tons) in the first and second seasons, respectively. While,
sorghum was the worst preceding crop for sugar beet in this
respect.
e. Technological characters:
1. Total soluble solids (T.S.S), sucrose and purity percentages were
significantly affected by preceding summer crops. cowpea as a
preceding crop for sugar beet gave the highest T.S.S, sucrose
and purity percentages in juice of roots in both seasons.
B.E”ectofn;~ogen/evels:
a. Growth parameters.
1. Leaf area per plant (L.A) and leaf area index (L.AJ) were
significantly increased with increasing nitrogen level up to 90
Kglfad at all growth stages. The highest values were obtained by
applying 90 Kg N/ fad at age of 163 days after sowing.
2. Total dry weight (gm) was significantly increased with increasing
nitrogen level. The maximum value was obtained at 90 Kg N/ fad.
and this result was true for all growth stages.
3. Crop growth rate (CGR) was significantly increased as nitrogen
level increased up to 90 Kg N/fad at the three growth periods.
4. Net assimilation rate (NAR) was significantly decreased as
nitrogen level increased up to 60 Kg Nlfad at the first and second
growth periods.
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5. Relative growth rate (RGR) was significantly increased by
increasing nitrogen level up to 60 Kg Nt fad, but excess nitrogen
over this level decreased it.
b. Root characters.
1. Root length was significantly increased by increasing nitrogen
fertilizer level up to 90 Kg Ntfad.
2. Root diameter was significantly increased with increasing
nitrogen level up to 60 Kg N/fad in both seasons.
3. Root weight was significantly affected by nitrogen levels in both
seasons. Increasing nitrogen levels up to 90 kg/fad caused a
gradual increase in root weight.
c. Yield:
1.Top yield (tons/fad) was significantly affected by nitrogen level in
both seasons. Increasing nitrogen application to sugar beet up to
90 kg Ntfad ’Consistently increased top yield/fad.
2. Root yield (tons/fad) was significantly increased by increasing
nitrogen level up to 90 kg N/fad in both seasons. The increase in
root yield of sugar beet was about 9.81 and 1’1.49 tonslfad in the
first and second seasons I resPectively:
3. Biological yield (Tons/fad) responded to nitrogen fertilization in
both seasons. Increasing nitrogen level increased significantly
the biological yield of sugar beet. The highest nitrogen level (90
kg/fad) produced the highest biological yields (28.63 and 29.31
tons/fad) in the first and second seasons. respectively.
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4. Sugar yield (tons/fad) was significantly affected by nitrogen level
in both seasons. Nitrogen fertilization significantly increased the
sugar yield /fad, and any increase in nitrogen applied was
followed by a respective increment in sugar yield.
d. Technological characters:
1. Total soluble solids percentage (T.S.S.%) and sucrose
percentages were significantly affected by nitrogen levels in both
seasons. Increasing nitrogen level up to 90 kg N/fad significantly
increased TSS and sucrose percentages in roots juice.
2. Purity percentage was not significantly affected by nitrogen levels
in both seasons.
c. Interaction effect:
1. The effect of the interaction between preceding summer crops
and nitrogen levels was significant on root yield, biological yield
(in both seasons) and sugar yield (ton/fad) (in the first season).
The maximum root, biological and sugar yield {fad were obtained
from growing sugar beet after cowpea with the application of 90
kg N/fad. While, the minimum values of root and biological yields
were produced from growing sugar beet after sorghum without
nitrogen fertilization. On the other hand, the minimum value of
sugar yield per feddan was produced from growing sugar beet
after maize without nitrogen fertilization.