الفهرس 
Materials and mithodsOnly 14 pages are availabe for public view
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Abstract
SUMMARY
The present work was carried out to study the effect of soil
moisture levels in combination with some growth regulators on growth,
yield and its components, evapotranspiration, crop coefficient, and
chemical composition of soybean plant. Therefore, field plot trials
were conducted in Agricultural Research Center, Giza farm during
the two successive seasons 1988 and 1989 using crawford soybean variety.
The design of the experiment was complete randomized block design
with four replications. The experiment consisted of 18 treatments
and included three soil moisture levels i.e. 85, 70, and 55 % of field
capacity. These three moisture levels were combined factorially with
two growth regulators i.e, GA) asa promoter at the rate of 0, 100
and 200 ppm and Alar as a retardant at three concentrations i.e.,
0, 1000 and 2000 ppm. Plants were sprayed twice when aged 20 and
30 days with the previous chemicals.
The main trend of results can be summarized as follows:-
L Gcowth behaviour :
1. Stem length increased by time from emergence up to 100
days after sowing, then it seemed to be constant after that. Water
deficit had a significant effect on stem length at all tested periods.
The use of GA3 at both levels increased stem length significantly.
However, Alar application reduced stem length especially by increasing
its concentration. It is worthy to mention that the effect of water
deficit is more effective than any other hormonal influence.
2. Leaf area/plant started with lower values at earlier period
of growth’ and increased gradually to reach a maximum when plants
aged 100 days. The wet treatment gave the highest values of leaf
area/plant followed by the medium level. Prolonged irrigation intervals
produced the lowest leaf area/plant. The application of GA3 did result
in a significant increase in total leaf area/plant compared with the.
control. Such increase was found to be obvious at higher GA3 rate
(200 ppm). On the contrary, the use of Alar caused a depressive effect
on leaf area/plant. The enhancing effect of GA3 was more pronounced
under wet conditions while the retarding effect of Alar seemed to
be o-bvious under waterdeficit.
3. The highest rate of dry matter accumulation in. roots was
found to be from 50 up to 75 days after sowing, while at later stages,
the rate was declined. High soil moisture level resulted in a significant
increase in dry matter of roots. GA3 application enhanced dry matter
accumulation and the lower rate (roo ppm) is the most pronounced
level. However, the use of Alar depressed such values. The reduction
was clear with the higher concentration. The enhancing effect of GA3
seemed to be Obvious under wet conditions while the reverse trend
was found to be true with Alar.
4. Stem dry matter showed higher values under wet conditions.
The use of GA~ enhanced such values. Using Alar with low concentration
enhanced the accumulation of dry matter of stem, while higher rate
(2000 ppm) reduced’ it. The promoting effect of GA3 seemed to be
clear under wet soil moisture, however, Alar needs dry conditions
to insure its effect.
5. The period from 50-75 days seemed to be the greatest stage
of dry matter accumulation in leaf petiol and blade. The effect of
different treatments’ on dry matter of both petiols and blades are similar
to that observed with stem.
6. The values of pods dry matter/plant were higher under wet
soil moisture Ievel and decreased by increasing water deficit. GA 3
application stimulated the dry matter of pods/plant and that was more
pronounced at lOO ppm rate. The use of Alar resulted in a retarding
effect on pod dry matter which was increased by high level. The effect
of growth regulators was controlled by the level of soil moisture.
7. Dry matter content of whole plant increased continously from
emergence till the last sample. The highest dry matter was produced
from wet level followed by the medium and the least values were
gained from the dry treatments. The lower rate of GA
3
(loa ppm)
enhanced dry matter production either over the control or the higher
rate. The use of the lower Alar rate increased dry matter content,
while the higher rate reduced dry matter accumulation.
8. Leaves comprise the main dry matter component throught
the first 50 days followed by stem while root ranked the third in this
respect. When plants aged 75 days, stem dry weight was superior followed
by leaf blade, pods and petiols while root value was the lowest one.
At 100 days, stem and pods dry matter were the domenant organs.
IL Soybean yield and its components:
1. Soil rnoistu re stress has a significant effect on different yield
components of soybean plant. Such characters were decreased
by water deficit. The application of GA3 stimulated the tested
yield components while Alar retarted them.
2. Maximum seed yield was obtained from the wet level followed
by the medium soil moisture and the least yield was produced
from the dry treatment. Foliar application of GA) did result
in a significant increase in seed production.
On the contrary Alar application decreased seed yield and
this was obvious by high concentration. The enhancing effect
of GA3 seemed to be clear under wet and medium soil moisture
level. However, in case of Alar, the retarding effect increased
by water deficit.
4. Statistical analysis showed that either water deficit or growth
substances had a significant effect on oil content of soybean
seeds.
5. Oil production increased by high soil moisture level and decreas-
. ed by water deficit. GA3 application increased oil production
and that was found to- be more by low level. The use of Alar
decreased oil yield and such decrease was greater by. higher
rate.
ilL i Evapotranspiration
1. Seasonal evapotranspiration by soybean varies widely between
49.57 and 84.09 ern. under the various treatments.
2. Evapotranspiration rates were increased as soil moisture
stress decreased.
:3. Growth promoting substance i.e, GA
3
increased seasonal ET.
values while retardant (Alar) decreased such values and that
was greater by high concentration.
iii. Daily water use by soybean started with lower amounts increased
gradually to a maximum when plants complete 70 % of its
growth cycle then declined after that. >
ii
5,· Daily water use by soybean can be represented as -a continous
function in- the form
y = a + bx + cx2
where
y = daily evapotranspiration mm/day
x = relative growth period as a percentage.
Such function predict daily ET. at any specific period of soybean
growth.
6 c. Crop coefficient (Kc) for soybean was very low at earlier
stages, then increased graduaJ1y to exceed the unit when soybean
.cornplete 70-80 % of its growth period. Thereafter, Kc values
redecreased again. GA3 application increased such values
while Ajar decreased it.
7” Water use efficiency was lower in the first period (from emergence
to 50 days) then reached a maximum through the period
from (50 & 75 days). Thereafter, water use efficiency values
redecreased again to reach a minimum at the end of the seasons
(f rom 100-1 30 days).
8. Water use efficiency expressed as Kg. dry matter/m 3 of water
consumed, was higher under high soil moisture level and decreased
by water deficit.
9,. The use of GA3 improved water use efficiency values under
high soil moisture level. However f under prolonged irr iga tion
intervals, no clear trend was observed. The use of retardant
Le, Alar, slightly decreased the values of water use efficiency.
10. Water use efficiency expressed as Kg. seeds/rn ’ of water
consumed was higher under wet conditions and decreased
by increasing soil moisture stress. The use of GA 3 at 100 ppm
improved the efficiency of water utilization while Alar depressed
such values.
IV. Water and Soybean Yield Relationships:
1. Statistical analysis showed that the relationship between soybean
yield and soil moisture level or seasonal water consumption
IS a first clear relation. The regression line has the form :
y = a + bx
2. The relation between the two factors i.e, actual evapotranspiration
and soil moisture level, and soybean yields demonstr-ates that
both factors affect the productivity of such crop. These relationships
have the form :
3. Results indicate that any environmental factor affecting seasonal
water consumption of soybean had a great response on its
production.
V. ~hemica1 Compositon:
:1. The level of soil moisture is an important factor controling
soybean protein. It was found that increasing soil moisture
stress resulted in increasing soybean protein. The use of growth
promoting substances (GA3) seemed to decrease the amount
of soybean protein while Alar increased such values.
The total content of different macronutrients i,e. NP K increased
with advancing age. Soil moisture levels and growth regulators
affected the total amount of tested nutrients in different
plant parts as well as the whole plant which decreased with
increasing soil moisture stress.
3. The total content of Fe, Mn and Zn seemed to be decreased
with the use of growth substances as well as water deficit.
It can be concluded that when growth substances were applied,
such micro-nutrients should be added to ensure their effect
as well as to regulate the balance between micro and macronutrients,