الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
SUMMARY
The present investigation was conducted to study the effect
of soil moisture stress and weed control treatments on dry weight
of weeds, growth, yield and its component, evapotranspiration, crop
coefficient and oil content of soybean plant. Therefore, field plot trials
were carried out in Agricultural Research Center, Giza farm during
the two successive seasons 1985 and 1986 using calland soybean variety.
The design of the experiment was split plot design with four replications.
Water deficit was arranged in the main plots and includes three soil
moisture levels i.e. irrigated at 0.5 - 0.6 bar, irrigated at 0.9 - 1.0
I bar and at 1.3 - 1.4 bars. However, the weed control treatments were
arranged randomly in the sub-plots and includes the following treatments:
1. Check (unweeded}.
2. Hand hoeing twice •
.,3. Hand weeding twice.
4. Pendimethalin (stomp) at the rate of 1.7 L./feddan.
5. Metribuzin (sencor) at the rate of 250 g./feddan.
6. Oxyflurfen (goal) at the rate of 0.7 L./feddan.
These chemicals were sprayed as a pre-ernergence (post-sowing)
herbicides.
The main trend of results can be summarized as follows:
1. Water regime had no significant response upon dry weight of weeds
in the two tested stages (60 - 90 days after sowing).
2. Increasing soil moisture stress caused a slight increase 10 total
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dry weight of weeds.
3. Weed control treatments exhibit a significant effect on dry weight
of weeds in the two tested per iods and the two seasons.
4. Hand hoeing treatment gave the highest depression in dry weight
of weeds.
5. Hand hoeing treatments is the most efficient method in controlling
soybean weeds.
6. Stomp and sencor were the most promosing herbicides in reducing
the dry weight of both broad-leaved and grass weeds at 60 days
from sowing.
7. Stomp or goal herbicides were more efficitive in controlling soybean
weeds at 90 days from sowing.
8. The effect of goal as a weed killer was extended to later stages
of soybean growth.
9. Water deficit induced a significant-effect on plant height at the
different growth -stages as well as at harvest time. The wet treatment
produced the tallest plants.
10. The control of weeds either by hoeing or by chemical herbicides
produced taller plants than the hand weeding treatment.
11. Leaf area of soybean plants started with lower values and increased
gradually up to 90 days after sowing.
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12. Maintaining soil moisture at a high level by frequent waterings
did result in higher leaf area values.
13. Maximum values of leaf area were obtained from hand hoeing
and stomp followed by other chemical herbicides.
14. The interaction between weed control treatments and water regime
with respect to leaf area was found to be significant.
15. The highest leaf area values were scored from treatments irrigated
at 0.5 - 0.6 bar and hand hoeing,
16. The accumulation of dry matter by soybean plant increased by
advancing age up to 90 days.
17. Resul ts gained f rom the two season showed the improtance of
high soil moisture level for maximum dry matter accumulation
by various organs of soybean plant.
18. The highest values of dry matter were obtained from hand hoeing
treatment foHowed by herbicides treatments in the two successive
seasons.
19. The use of stomp, sencor or goal decreased the dry weight of
various organs of soybean plant than .hand hoeing treatment.
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20. The maximum dry matter produced from different organs of soybean
plant as well as the whole plant was from the wet treatment and
hand hoeing.
21. Soil moisture stress had no significant effect on number of branches
of soybean in the two seasons.
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22. Weed control treatments had a significant effect on number of
branches of soybean plant in one season only.
23. Hand hoeing or hand weeded gave the’ highest number of branches/
plant, while the thsee chemical herbicides are less in such effect.
24. Soil moisture stress had a significant effect on number of pods/
plant, weight of pods/plant, weight of seeds/plant and seed index.
25. The wet treatment produced the highest values of the previous
yield component characters and differ significantly from the other
two soil moisture stress treatments.
26. Weed control treatments had a significant effect on No. of pods/
plant, weight of pods/plant, weight of seeds/plant arjd seed index.
27. The hand hoeing treatment produced the highest values of the
previous yield component characters.
28. Stomp and goal did not differ significantly than the hand hoeing
treatment with respect to, yield component but their values were
less than the hand hoeing.
29. The use of sencor herbicide reduced significantly the yield component
characters compared with hand hoeing treatment.
30. Soil moisture stress had a significant effect on seed yield of soybean
plant.
31. The wet treatment produced the highest seed yield/feddan followed
by the medium level and the lowest yield was obtained from the
dry treatrnent_
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32. Soil moisture stress had a similar trend on biological yield to that
observed with seed yield.
33. Weed control treatments exhibited a significant effect on seed
yield/feddan and biological yield/feddan of soybean.
34. The hand hoeing treatment produced the maximum seed yield.
35. The use of either stomp or goal increased yield of soybean than
the check but less than the hand hoeing.
36. Sencor herbicide increased seed yield of soybean than the control
but reduced it compared with the other two herbicides.
37. Seasonal evapotranspiration by soybean plant vary widely between
48.16 and 84.07 em. under the different treatments.
38. Water consumptive use by soybean was increased as soil moisture
stress decreased. The rate of evapotranspiration increased in an
ascending order :
Dry < Medium < Wet soil moisture levels.
39. The check treatment (unweeded) consumed much more water than
the other weed control treatments.
40. The control of weeds by hand hoeing decreased seasonal water
use by soybean plant than the hand weeded treatment.
41. The elimination of weeds by chemical herbicides decreased seasonal
values of water consumption by soybean plant than the check treatment.
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42. The use of goal as a weed control herbicide reduced seasonal water
use of soybean plant by 4- % than the hand hoeing treatment.
4-3. Daily evapotranspiration rates by soybean were lower early in
the season, and increased as the plants developed to reach a maximum
when plants aged 70 - 100 days. A decline in dally rates occured
at the end of the growing season.
4-4-. Soil moisture stress induced a negative response on daily rates
by soybean plant. Increasing water deficit did result in decreasing
such values.
4-5. Estimates of potential evapotranspiration by Turc method were
lowere than those obtained from Penman formula.
46. The values obtained from penman’s method can be axcepted as
the best estimate of potential evapotranspiration.
(17. Seasonal crop coefficient (K)c for soybeCih· ranged from 0.75 -
1.14 • It differs under the various treatments as well as the method
used in estimating potential evapotranspiration.
48. The presence of weeds (check) caused an increase In the values
of crop coefficient.
49. Water use efficiency (kg. dry matter/m” of water consumed) was
lower early in the season when the plant vegatation was not established
yet, then increased gradually to reach a maximum value during
the period of flowering and pod formation. Thereafter, the efficiency
of water use redecreased again to a minimum value when plants
stan to mature.
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50. Water use efficiency values were higher under wet or medium
soil moisture stresses and decreased under severe water deficits
through the periods from planting till flowering and pod formation.
At later stages of soybean growth, water use efficiency increased
as soil moisture stress increased and ’the revers trend was true.
51. The control of weeds either by hoeing or by chemical herbicides
improved greatly the values of water use efficiency at the first
and second periods of growth (from planting to flowering and pod
formation). Hand hoeing treatment was soperior in such respect.
52. Water use efficiency expressed as Kg. seeds/m? of water consured
decreased as soil moisture stress increased. The existance of
weeds with soybean plant caused a sharp reduction in water use
efficiency values (Kg. seeds/rn ’ water).
53. The hand hoeing or the use of goal herbicides improved the values
of water use efficiency over hand weeded or either storrp or sencer.
54. Increasing soil moisture stress did result In a significant decrease
on oil content of soybean seeds.
55. The maximum oil content was gained from the stomp and goal weed
control treatments. However, the lowest value of oil percentage
was found to be from the check, had weeded and those sprayed
with sencor .
56. Results from the following crop (Berseem) had shown that the
use of stomp, sencor, or goal at the used rates had no residual
effect and can be applied without any side effect.