Vol.2, No.3, 262-266 (2011)
doi:10.4236/as.2011.23034
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
Agricultural Scienc es
Effect of water stress at different periods on seed yield
and water use efficiency of guar under Shambat
conditions
Mahmoud Fadl El Mula Ahmed*, Deng Manasseh Mac, Awatif Abdel Gadir Bashir
Faculty of Agriculture, University of Khartoum, Shambat, Sudan; *Corresponding Author:
Received 13 January 2011; revised 21 April 2011; accepted 2 July 2011.
ABSTRACT
W a ter s tre ss ef fects on s eed y i eld and water use
efficiency of three indeterminate guar (Cya-
mopsis tetragonoloba L. Taub.) lines (L12, L18
and L33) were investigated in the experimental
farm of the Faculty of Agriculture, University of
Khartoum for two seasons (2005 and 2006). The
guar lines were subjected to water stress in-
duced by withholding irrigation for three weeks.
Three water stress treatments w ere imposed 35,
50 and 65 days after sowing (DAS), and a con-
trol treatment irrigated every two weeks. The
treatments were arranged in a split-plot design
with three replications; with water regime treat-
ments assigned to the main plots and guar lines
to the sub-plots. Data were recorded on seed
yield (t·ha–1), number of pods per plant, 1000-
seed weight (g), harvest index (HI) and water
use efficiency at harves t.
The results indicated that exposure of several
cultivars of guar to water stress at the three
stages of growth didn’t induce any significant
effect on number of pods per plant, 1000-seed
weight, seed yield and water use efficiency
(WUE). On the other hand there was significant
reduction in harvest index as a result of imposi-
tion of water stress at 35 an d 50 DAS. I t was also
evident that plants re-watered after the stress
recovered and had the same values as the con-
trol treatm e nt.
Keywords: Guar; Water Stres s; Wate r Use
Efficiency; Harvest Index
1. INTRODUCTION
Guar [Cyamopsis tetragonoloba (L.) Taub.] grains are
a source of guar gum which has many uses in food, pa-
per manufacturing, textile printing, and pharmaceutical
industries. Nevertheless, the best known use is as a fric-
tion-reducing additive in drilling mud in petroleum oil
production [1].
The bulk production of guar is in the arid and semiarid
zones of India, Pakistan, USA, Australia and Africa,
where rainfall is the most important yield and growth
determining environmental factor. Guar is generally
considered as a drought tolerant crop; few studies have
shown that water stress experienced during critical
growth stages can lead to substantial reduction of seed
yield. Boutraa and Sanders in 2001 [2] reported that wa-
ter stress during both flowering and pod-filling stages
decreased seed yield. It was also found that moisture
stress at flowering stages was more detrimental for ob-
taining higher pod yield [3].
Crop water use efficiency (WUE) is defined as the ra-
tio of seed yield to water used (consumptive use of wa-
ter). However, it was observed that WUE might not pro-
vide much information about the competitive or yield
advantage of one particular species over another because
improved WUE may actually restrict growth with rela-
tively small increments in yield and still WUE, as a ratio,
is improved [4]. Crop yield was defined by [5] for water
limited environment as: “water transpired, while in-
crease in WUE, and harvest index” may result in in-
crease in yield, although these three values are inde-
pendent of each other.
Several studies have reported considerable variation in
WUE among crop plants. However, under optimum wa-
ter management practices [1] reported that water use
efficiencies expected for guar crop ranged from about
0.40 to 0.60 kg·m–3.
In the Sudan, although guar production is gaining
ground, there is very little information on its efficiency
of water use under drought conditions. However, it is
worth noting that, under biological studies, experimental
results are always location and environment dependent.
Thus, there is a need for more studies to identify stages
at which cultivars are more tolerant to water stress and
those ones which are more efficient in their water use.

M. F. El M. Ahmed et al. / Agricultural Science 2 (2011) 262-266
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263263
The aim of this study, therefore, was to investigate the
effect of water stress on seed yield and WUE of irrigated
guar under Shambat conditions.
2. MATERIALS AND METHODS
A field trial was conducted under irrigation for two
consecutive seasons (2005 and 2006), at the experimen-
tal farm of the Faculty of Agriculture, University of
Khartoum, Shambat, Sudan, Located at latitude (15˚40′)
N, Longitude (32˚32′) E, and altitude 380 m above sea
level. Land was prepared by disc ploughing, harrowing,
leveling and ridging.
The experimental material consisted of three indeter-
minate guar lines coded L12, L18, and L33 and four water
regimes namely, WS1 (stressed at 35 DAS), WS2
(stressed at 50 DAS), and WS3 (stressed at 65 DAS) and
the (control treatment WS0) which was never stressed
and irrigated every two weeks. Water stress was imposed
at a particular period, by withholding irrigation for three
weeks and then irrigated as in control (WS0).
The trial was laid out in a split plot design replicated
three times with plot size of 12 m2. Water regime treat-
ments were assigned to main plots, and guar lines were
assigned to the subplots. Sowing was on the third of July
in both seasons, at a spacing of 0.70 m between rows
and 0.40 m between plants within rows.
The crop was kept weed free by hand weeding at 21
and 33 DAS in the two seasons and no pests or diseases
were observed in both seasons.
In both seasons records were taken for the number of
pods per plant, 1000-seed weight, grain yield harvest
index and crop water use efficiency (WUE). The evalua-
tion of water use efficiency (WUE) was based on the
relation between consumptive use (CU), and seed yield
for each water regime treatment in both seasons.
Harvesting was on Nov. 2, 2005 (121 DAS) in the first
season, and Oct. 28, 2006 (119 DAS) in the second sea-
son.
Analysis of variance was based on the general linear
model procedures of the Statistical Analysis System
(SAS). The least significant difference (LSD) at 0.05
level of probability was used to detect means differences
between treatment means
3. RESULTS AND DIS CUSSION
3.1. Number of Pods per Plant
There were no significant differences in the number of
pods per plant under the water regime treatments in both
seasons, (Ta bl e 1 ). However, treatment WS2 (withhold-
ing irrigation at 50 DAS) showed a tendency to reduce
average number of pods per plant compared to the rest of
treatments in both seasons. Several workers reported that
water stress caused more shedding of flowers, immature
pods and smaller seeds, e.g. [2]. However, in this ex-
periment, stressed plants at 65 DAS did not show this
response. Increased amounts of irrigation water or sam-
pling errors are possible reasons for this clear discrep-
ancy. Moreover, [6] reported that pod density was most
affected by water stress, among yield components with
pod reduction averaging more than 50%, mainly due to
the reduced flower production and the greater abortion
of flowers.
Line L12 produced more pods per plant compared with
the other two lines (L18 and L33) which were not signifi-
cantly different. This result may suggest that lines L18
and L33 were more susceptible to water stress than line
L12.
3.2. 1000-Seed Weight (g)
On average, the weight of 1000 seeds was not signifi-
cantly affected by the different water regimes in both
seasons (Ta b l e 2). This result is in line with that of [7]
who found no effect of drought on mean faba bean seed
weight. There was no effect of the treatments on seed
weight as was reported by [8] in their experiment, which
indicates that the seed size was not affected by the stress.
On the other hand, the present result is in disagreement
with the finding of [9] who reported a decrease of about
34% in the mean seed weight of the stressed faba bean
plants, compared to the fully irrigated treatment. Reduc-
Table 1. Average number of pods per plant as affected by water stress and guar lines during the two seasons (2005 and 2006).
Season (2005) Season (2006)
Lines Lines
Treatment
L12 L
18 L 33 Mean LSD (0.05) L12 L 18 L 33 Mean LSD (0.05)
WS0 147.9 108.9 130.7 129.1A 142.2 82.6 74.1 99.7A
WS1 197.2 83.8 161.9 147.6A 130.6 100.2 53.7 94.9A
WS2 114.6 100.6 156.6 123.9A 76.9 74.2 109.3 86.8A
WS3 173.2 118.3 120.8 137.4A
n.s
107.2 92.9 63.7 87.9A
n.s
Mean 158.2a 102.8b 142.4ab 114.3a 87.5a 74.2a
LSD (0.05) 44.94 n.s
Means with the same letter(s) in a column or a row are not significantly different at LSD = 0.05; WS0 = control treatment (irrigated every two weeks), WS1 =
stressed at 35 days after sowing, WS2 = stressed at 50 DAS and WS3 = stressed at 65 DAS.

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Table 2. Average 1000-seed weight (g) as affected by water stress and guar lines during the two seasons (2005 and 2006).
Season (2005) Season (2006)
Lines Lines
Treatment
L12 L
18 L 33 Mean LSD (0.05)L12 L 18 L 33 Mean LSD (0.05)
WS0 30.0 30.6 31.3 30.6A 32.0 33.0 33.8 32.9A
WS1 31.3 31.6 35.6 32.8A 32.2 31.4 31.7 31.8A
WS2 30.3 30.6 34.0 31.6A 29.7 31.0 34.6 31.7A
WS3 29.0 31.3 31.2 30.5A
n.s
31.6 31.6 33.2 32.1A
n.s
Mean 30.1b 31.0b 33.0a 31.4b 31.7b 33.3a
LSD (0.05) 1.95 1.30
Means with the same letter(s) in a column or a row are not significantly different at LSD = 0.05; Legends are as in Table.
Table 3. Average seed yield (t·ha–1) as affected by water stress and guar lines during the two seasons (2005 and 2006).
Season (2005) Season (2006)
Lines Lines
Treatment
L12 L
18 L 33 Mean LSD (0.0)L12 L 18 L 33 Mean LSD (0.05)
WS0 2.6 1.8 1.6 2.0A 2.1 1.3 1.2 1.5A
WS1 2.8 0.8 1.2 1.6A 1.5 1.4 1.0 1.3A
WS2 2.0 1.5 2.8 2.1A 1.3 1.2 1.6 1.4A
WS3 2.2 1.2 1.8 1.7A
n.s
2.2 1.5 1.1 1.6A
n.s
Mean 2.4a 1.4b 1.8ab 1.8a 1.3a 1.2a
LSD (0.05) 0.67 n.s
Means with the same letter(s) in a column or a row are not significantly different at LSD = 0.05; Legends are as in Table 1.
tion in seed size was found by earlier workers e.g. [10-
12]. Although seed weight is a known component of
yield, which reflects relationship between source and
sink of photosynthate during pod filling stage, and it is
where compensation for earlier losses of pods may occur,
thus enhancing the final yield [13].The results of the
present study are negating this fact, probably because the
magnitude of the stress (between the control and the
stressed treatments) was not so acute to disrupt or slow
down the assimilate supply (translocation process) to the
pods of the stressed plants.
The three guar lines were significantly different in
1000 seed weight in both seasons. However, higher av-
erage weights (33.0 and 33.3 g) were recorded for line
L33 than the other two lines (L12 and L18).This may be
attributed to fewer pods per plant. This explanation is
supported by the finding of [14] that attributed greater
kernel weight to fewer kernels set due to water stress at
flowering and better grain filling in the presence of
fewer kernels per ear.
3.3. Seed Yield
Seed yield was not significantly affected by different
water regimes in both seasons (Table 3). This was due to
the fact that the most important components of the yield
(number of pods per plant and 1000-seed weight), in this
study, were not significantly affected by the water stress
imposed at 35 DAS and above. Nevertheless, treatment
WS1 (withholding irrigation at 35 DAS) gave the lowest
seed yield (1.6 and 1.3 t·ha–1) in the first and second
seasons, respectively. This was probably due to negative
effect of water shortage on the vegetative growth espe-
cially plant height and number of main branches per
plant (data not shown) which had resulted in low number
of pods per plant. Similar findings on sesame were re-
ported by [15] as they reported that yield per plant was
significantly and positively correlated with stem height
and number of branches.
The insignificant difference in seed yield between L12
and L33 was due to the fact that yield in the former line
was a function of number of pods per plant, whereas in
the latter was a function of seed weight. This trend was
observed in the second season, but line L12 gave higher
seed yield than the other two lines.
Seed yield was greater in the first season than in the
second season, due to high number of pods per plant, as
a result of high number of branches per plant. Relating
this observation to weather conditions (Ta bl e 4) during
the growing period, it could be concluded that high seed
yield was associated with a combination of high water
supply (rainfall) and low evaporative demand especially
during the early growth stages.
3.4. Water Use Efficiency (WUE)
The data presented in Table 5 seem to indicate that
stopping irrigation during any one phase of the life cycle
of guar plant does not have any significant change on
seed yield and eventually on the crop water use effi-
ciency (WUE). This result is in accordance with obser-
vation of [7] who found that faba bean water use effi-
ciency was similar among different irrigation treatments
since the seed and straw yield linearly depended on total
water received. The data also indicated that line L12 is
ore efficient in its water use than the other two lines m

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Table 4. Average harvest index (H.I) of guar as affected by water stress during the two seasons (2005 and 2006).
Season (2005) Season (2006)
Lines Lines
Treatment
L12 L
18 L 33 Mean LSD (0.05)L12 L 18 L 33 Mean LSD (0.05)
WS0 39.9 30.2 28.1 32.7A 47.1 41.9 38.0 42.3A
WS1 34.2 18.0 23.2 25.1A 42.4 42.9 37.2 40.8A
WS2 32.4 33.2 40.1 35.2A 36.4 35.8 31.0 34.4A
WS3 40.1 22.9 25.9 29.6A
n.s
40.4 40.9 34.7 38.7A
n.s
Mean 36.7a 26.1b 29.3b 43.2a 40.4ab 35.3b
LSD (0.05) 5.47 6.07
Means with the same letter(s) in a column or in a row are not significantly different at LSD = 0.05; Legends are as in Table 1.
Table 5. Mean water use efficiency (WUE) kg·m–3 as affected by water stress and guar lines during the two seasons (2005 and 2006).
Season (2005) Season (2006)
Lines Lines
Treatment
L12 L
18 L 33 Mean LSD(0.05 L12 L 18 L 33 Mean LSD (0.05)
WS0 0.5 0.3 0.3 0.4A 0.4 0.2 0.2 0.3A
WS1 0.6 0.1 0.2 0.3A 0.3 0.3 0.2 0.2A
WS2 0.4 0.3 0.6 0.4A 0.2 0.2 0.3 0.3A
WS3 0.4 0.2 0.4 0.3A
n.s 0.5 0.3 0.2 0.3A n.s
Mean 0.5a 0.3b 0.4ab 0.3a 0.3a 0.2a
LSD (0.05) 0.14 n.s
Means with the same letter(s) in a column or a row are not significantly different at LSD = 0.05; Legends are as in Table 1.
(L18 and L33).
3.5. Harvest Index (HI)
HI (seed yield as a ratio of the total weight of seeds
plus straw) was significantly reduced under treatments
WS1 and WS2 as a result of low seed yield (Table 3).
This result confirms the finding reported by [16], in an
experiment at Shambat, attributed the reduction in (HI)
of faba beans under water stress during vegetative stage
to low seed yield, and attributed the reduction at pod set
stage to the effect of drought on the assimilate supply.
Moreover, the reduced (HI) under treatment WS2 in the
present investigation is in accordance with the findings
of [17] who attributed the reduction in (HI) in common
bean to the effect of water stress imposed during repro-
ductive stage.
There was genotypic difference among the three lines
regarding the harvest index. On average, line L12 gave
high harvest indices of 36.7 and 43.2, in the first and
second seasons, respectively. This finding indicates that
line L12 was high yielding under the conditions of the
present investigation. However, the two other lines (L18
and L33) were not significantly different and can be
graded as low seed yielding.
It can be concluded that irrigation treatments did not
significantly affect the measured attributes of growth
and seed yield. However, the three guar lines showed
significant variation, with line (L12) being more superior
to the other two.
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