Effect of varying Irrigation Frequencies on Growth, Yield and Quality ...

<strong>Effect</strong> <strong>of</strong> irrigation frequencies on pea
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EFFECT OF VARYING IRRIGATION FREQUENCIES ON
GROWTH, YIELD AND QUALITY OF PEA SEED
Irfan Ashraf, M. A. Pervez, M. Amjad* and R. Ahmad**,
ABSTRACT
<strong>Effect</strong> <strong>of</strong> various irrigation frequencies on pea seed yield and seed quality was
investigated under field conditions at the Institute <strong>of</strong> Horticultural Sciences,
University <strong>of</strong> Agriculture, Faisalabad, Pakistan during the years <strong>of</strong> 2005-06 and
2006-07. Two promising pea cultivars i.e. Meteor and Climax were tested in
these investigations. Four irrigation levels i.e. 8 irrigations upto flowering (I 1):
10 irrigations upto pod filling (I 2): 12 irrigations upto seed filling (I 3) and 13
irrigations upto seed maturity (I 4) were applied. Each irrigation (7.5 cm) was
applied at ten days interval. The data on stem length, number <strong>of</strong> leaves per
plant, leaf area , number <strong>of</strong> pods per plant, number <strong>of</strong> seeds per pod, seed
fresh weight per plant, seed dry weight per plant, 1000-seed weight and seed
yield per hectare were recorded. Quality <strong>of</strong> pea seeds was checked by
germination percentage, emergence percentage and electrical conductivity.
The results indicated that cultivar Meteor produced significantly higher seed
yield (2.5 t/ha) in treatment I 3 (12 irrigations upto seed filling) while Climax
gave maximum yield (2.2 t/ha) in I 4 (13 irrigations upto seed maturity). On
overall basis Meteor performed better than Climax for all vegetative and
reproductive traits. For quality parameters cultivar Climax was found better.
KEYWORDS: Pisum sativum, irrigation scheduling; vegetative maturity;
reproductivity; yield; quality; Pakistan.
INTRODUCTION
Pea (Pisum sativum L.) a grain legume belongs to the fabacae family. It is a
native <strong>of</strong> central or Southeast Asia (34) and is widely cultivated in temperate
regions for its fresh green seed. Pea is an excellent human food, either
eaten as vegetable or used in soup preparation. The pea is rich in nutrition
because its grain is affluent in protein (27.8%), tortuous carbohydrates
*Institute <strong>of</strong> Horticultural Sciences, **Department <strong>of</strong> Crop Physiology, University <strong>of</strong>
Agriculture, Faisalabad, Pakistan.
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(42.65%), vitamins, minerals, dietary fibres and antioxidant compounds (31).
Peas rank fourth in the world on production basis (441.53 thousand tons)
among grain legumes after soybean, groundnut and french beans and is
grown on an area <strong>of</strong> 528.71 thousand hectares in the world (4).
In Pakistan, pea is an important crop <strong>of</strong> the Punjab province and enjoys a
great commercial demand for its nutritive value. It is cultivated on 10
thousand hectares with a total production <strong>of</strong> 82 thousand tons in Pakistan
(3).
Shortage <strong>of</strong> water is the most terrible constraint for agricultural development
in arid and semi-arid areas. Under these conditions, demand to use the
available water economically and expeditiously is unquestionable in
Pakistan. Acute shortage <strong>of</strong> irrigation water and drought are adversely
affecting crop production in general and vegetable production in particular.
Fougereux et al. (10) reported that water stress during the flowering period
<strong>of</strong> pea crop did not reduce seed quality but reduced seed yield slightly. They
stated that pea seed yield was closely related to pod number per unit area,
which was also strongly related to water stress. Martin and Jamieson (15)
found that number <strong>of</strong> seeds per pod was unaffected by water stress.
Similarly, moisture stress during seed development can substantially
decrease the amount <strong>of</strong> viable pea seed production (22). Mostly the
research on irrigation management for pea production has dealt with
sensitivity to moisture stressed specific growth stages (21, 25). Pea yields
<strong>of</strong>ten are increased by irrigation during vegetative and reproductive growth,
when soil moisture is otherwise limiting (11). However, few studies have
examined the effects <strong>of</strong> irrigation on spring pea seed yield (26, 34, 36) and
quality (5, 7, 12, 20). The effect <strong>of</strong> irrigation has been reported by Salter
(23, 24) at Wellesbourne, Warwickshire and in USA by Pumphrey and
Schwanke (21). Deficient irrigation reduced seed yield more than excessive
irrigation, whereas excessive irrigation caused the greatest reduction <strong>of</strong> seed
quality.
In Pakistan, annual peas seed requirement is 588 tons and due to nonavailability
<strong>of</strong> quality seed, the country is spending about Rs.159.00 million
on the import <strong>of</strong> peas seeds annually (2). Seed quality can be increased by
careful management <strong>of</strong> seed crops in the field by wise irrigation scheduling.
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<strong>Effect</strong> <strong>of</strong> irrigation frequencies on pea
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This study was conducted to investigate the effect <strong>of</strong> irrigation frequencies
on growth, yield and quality <strong>of</strong> pea seed. In addition, efforts were also made
to determine the effect <strong>of</strong> irrigation on physiological aspects <strong>of</strong> produced
seed like germination capacity and vigour.
MATERIALS AND METHODS
This study was conducted at the Institute <strong>of</strong> Horticultural Sciences,
University <strong>of</strong> Agriculture, Faisalabad, Pakistan during the year 2005-06 and
2006-07. Layout system for field experiments was RCBD with factorial
arrangements and CRD was used for seed vigour tests in laboratory. Pea
crop (cvs. Climax and Meteor) was sown on 2 nd November, 2005 at a
distance <strong>of</strong> 20 cm on beds made 150 cm apart. Each sub-plot was 1.5 m
wide and 5.71 m long (8.565 m 2 ). Standard dose <strong>of</strong> N @ 80 kg per hectare
alongwith 120 kg P and 100 kg K was applied. Phosphorus, potash and half
dose <strong>of</strong> nitrogen were applied at the time <strong>of</strong> seed bed preparation and
remaining N was applied when flowering started. Immediately after sowing,
water was applied. <strong>Irrigation</strong>s (7.5 cm each) were applied on different crop
growth stages, with ten days intervals as per schedule comprising four
treatments viz. 8 irrigations upto flowering (I 1 ), 10 irrigations upto pod filling
(I 2 ), 12 irrigations upto seed filling (I 3 ) and 13 irrigations upto seed maturity
stage (I 4 ). Crop was looked after properly and harvested on 22 nd May, 2006.
Data on main stem length (cm), number <strong>of</strong> leaves per plant, leaf area (cm 2 ),
number <strong>of</strong> pods per plant, number <strong>of</strong> seeds per pod, seed fresh weight per
plant (g), seed dry weight per plant (g), 1000-seed weight (g) and seed yield
per hectare (tons) were recorded. The seed vigour tests like electrical
conductivity, germination and emergence percentages were also performed.
These tests were also performed after harvest and quality <strong>of</strong> seed was
observed. Weather data were recorded for the year 2005-06 and 2006-07
seasons (Table 1). The year 2006-07 remained cooler because <strong>of</strong> higher
rainfall which resulted in higher humidity and thus overall cooler environment
prevailed during second year <strong>of</strong> the experiment.
Table 1. Mean monthly temperature (°C), relative humidity and total rainfall received
during crop growth.
Temperature (°C) Relative humidity (%) Rainfall (mm)
Months 2005-06 2006-07 2005-06 2006-07 2005-06 2006-07
Nov 20.8 20.9 50.5 47.0 0.0 12.8
Dec 14.6 15.5 52.0 57.4 0.0 46.2
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Jan 13.5 12.5 58.1 67.4 8.2 0.0
Feb 20.3 15.5 52.4 67.1 14.6 55.9
Mar 21.4 19.4 40.7 47.0 37.0 41.3
Apr 29.2 28.9 23.4 35.1 0.0 0.0
May 34.8 32.2 23.9 25.0 24.0 0.0
Source: Crop Physiology Department, Meteorological Station, University <strong>of</strong> Agriculture,
Faisalabad.
RESULTS AND DISCUSSION
Main stem length (cm)
The data (Table 2) revealed that on the basis <strong>of</strong> two years average, both the
cultivars performed significantly better in I 3 treatment (12 irrigations upto
seed filling). Meteor had more main stem length (58.0 cm) than Climax (55.0
cm) in this treatment. Treatment I 4 (13 irrigations upto maturity) stood second
in case <strong>of</strong> both cultivars (Climax 54.9 cm and Meteor 54.5 cm), while I 1 (8
irrigations upto flowering) produced the shortest stem length (Table 2). The
data further showed that both cultivars produced higher stem length during
second year <strong>of</strong> study i.e. 2006-07 (Meteor 58.0 cm and Climax 57.2cm) due
to higher rainfall. Availability <strong>of</strong> moisture to plants during the year 2006-07
enhanced the plant health and vigour which resulted in more stem length.
Similar findings have been reported by Hsio et al. (13) who observed that
water stress was a limiting factor for proper plant growth. These results
partially contradict the findings <strong>of</strong> Salter (23) who noted positive response <strong>of</strong>
irrigation till flowering in peas.
Number <strong>of</strong> leaves per plant
Significantly maximum number <strong>of</strong> leaves per plant was recorded in treatment
I 3 (irrigation upto seed filling stage) in case <strong>of</strong> both cultivars (Table 2). In this
treatment Meteor had more number <strong>of</strong> leaves (67.1) than Climax (61.5)
followed by treatment I 4 (irrigation upto seed maturity stage) (65.5 in Meteor
and 60.8 Climax). As far as years effect is concerned both cultivars gave
more number <strong>of</strong> leaves in the year 2005-06 (64.0) and stood at par. The
results further revealed that irrigation upto flowering did not prove its worth.
Vegetative growth was more sensitive to water stress than reproductive
growth in peas. Peas are an indeterminate plant and flowering, pod filling
and vegetative growth can occur simultaneously. There is competition for
assimilate between these processes and the response <strong>of</strong> yield components
will vary according to the relative strengths <strong>of</strong> the sources and sinks for
assimilates. Salter (24) and Maurer et al (17) found excessive vegetative
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<strong>Effect</strong> <strong>of</strong> irrigation frequencies on pea
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growth where water stress was avoided. The present results are also in line
with those <strong>of</strong> Hsio et al. (13) who reported that water stress during growing
stage reduced the growth <strong>of</strong> pea plants.
Leaf area (cm 2 )
Results <strong>of</strong> leaf area (cm 2 ) were found similar to those <strong>of</strong> number <strong>of</strong> leaves
per plant. Maximum leaf area was observed in treatment I 3 in case <strong>of</strong> both
cultivars. Meteor cultivar had comparatively more leaf area (246.0 cm 2 ) than
Climax (241.0 cm 2 ) (Table 2). These results are similar to those <strong>of</strong> Hsio et al
(13) who reported that water stress reduces growth via affection cell
expansion. In experiments with two pea cultivars, Salter (23, 24) also
observed a response to irrigation at flowering but not to application <strong>of</strong> water
in dry conditions during the vegetative growth stage.
Number <strong>of</strong> pods per plant
In this trait also both cultivars produced more number <strong>of</strong> pods per plant
(Meteor 25 and Climax 22.3) in I 3 i.e. irrigations upto seed filling stage
followed by I 4 i.e . irrigations upto seed maturity in case <strong>of</strong> Meteor (23.5) and
I 2 in case <strong>of</strong> Climax (21.5) (Table 3). For years effect, Climax gave more
number <strong>of</strong> pods per plant during the year 2005-06 (22.1) than the year 2006-
07 (19.8). However, Meteor produced similar number <strong>of</strong> pods during both
years (22.7) which was higher than Climax.
<strong>Irrigation</strong> upto flowering (I 1 ) produced the lowest number <strong>of</strong> pods (17.2)
during the year 2006-07. <strong>Irrigation</strong> at any growth stage increased the yield <strong>of</strong>
Meteor. The highest yields for this cultivar were achieved where irrigation
was applied throughout the season but these results did not differ
significantly from other irrigation treatments where less water was applied.
There was also a more effect <strong>of</strong> irrigation on Meteor cultivar than Climax. .
As in the previous year, Meteor was also more responsive to irrigation at
vegetative stage than Climax and overall. In this experiment, water stress
might have a stronger effect on reducing the number <strong>of</strong> pods/unit area than
on leaf area development. The low yields were associated with low number
<strong>of</strong> pods, nodes/stem and pods/node and a slower increase in pod weight
(19). Whether these changes would affect the balance between sources and
sinks, is uncertain. The resulting source-sink relationships during the filling
phase would then have been quite different for early and late drought plots
experienced. Consequently, there may have surplus photosynthates to fill
the peas in treatments with low pea numbers perunit area despite less
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favourable conditions for growth. Moisture stress during seed development
can substantially decrease the amount <strong>of</strong> viable pea seed production (22).
Martin and Jamieson (15) reported that water stress during the last half <strong>of</strong>
growing season (pollination, pod and seed formation periods) was a major
factor in reducing seed yield in temperate dry areas. Water stress during
seed filling decreased seed yield and seed quality while, stress during seed
filling reduced seed size (7), seed per unit area and yield can be reduced by
short periods <strong>of</strong> stress during flowering and pod set (32).
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Number <strong>of</strong> seeds per pod
On the basis <strong>of</strong> two years mean, cultivar Meteor produced more number <strong>of</strong>
seeds (6.1) in I 3 (12 irrigations upto pod filling stage) while Climax gave more
seeds (5.6) in I 4 (13 irrigations upto seed maturity stage) (Table 3). As far as
year effect is concerned, both cultivars gave higher number <strong>of</strong> seeds during
the year 2006-07 where Meteor surpassed (6.5 seeds/pod) the Climax (6.0).
During the year 2005-06 both these cultivars gave less number <strong>of</strong> seeds per
pod i.e. Climax 4.3 and Meteor 4.6.
Pea seed yield was closely related to pod number per unit area and water
stress. The number <strong>of</strong> seeds per pod was unaffected by water stress (15).
Water stress initiated during vegetative or early reproductive growth <strong>of</strong>
soybean usually reduced yield by reducing number <strong>of</strong> seeds per unit area
(6), while stress during seed filling reduced seed size (7), seeds per unit
area and yield can be reduced by short periods <strong>of</strong> stress during flowering
and pod set (32). The major portion <strong>of</strong> this yield reduction was related to
fewer seeds being produced (8, 12).
1000-seed weight (g)
In this trait, both cultivars performed significantly better in treatment I 4
(irrigations upto seed maturity) (Meteor 251.5 and Climax 250.2 g) followed
by I 3 (irrigations upto seed filling stage) (Meteor 242.5 and Climax 241.9 g)
(Table 3). Increased water use efficiency with increasing water stress has
also been observed in lentils by Mckenzie and Hill (18) reflecting the lower
soil evaporation component <strong>of</strong> water use without irrigation. Water use
efficiencies in this study are similar to those reported by Zain et al (37).
Vieira et al. (33) reported yield reduction <strong>of</strong> 35-41 percent when drought
stress was imposed during seed filling in green house experiment but found
no effect on germination. Drought stress resulted in significantly inferior
quality seeds as compared to well watered control plants. <strong>Irrigation</strong> during
full reproductive period was required for maximum seed yield and
germination <strong>of</strong> harvested seed (12).
Seed fresh weight per plant (g)
Maximum seed fresh weight was noted in case <strong>of</strong> Meteor in treatment I 1
(88.4 g) which was statistically similar to I 4 (88.2 g) (Table 4). However,
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Climax performed better in I 4 (89.0 g). For years effect, both cultivars on the
basis <strong>of</strong> two years mean, gave more seed fresh weight during the year
2006-07 as compared to 2005-06.
Seed dry weight per plant (g)
The data (Table 4) further showed that Meteor stood first for this trait in
treatment I 4 (66.0 g) while Climax (65.1 g) ranked second. It was followed by
treatment I 3 (Meteor 64.5 and Climax 63.5 g). Treatment I 4 differed
significantly from other irrigation treatments in case <strong>of</strong> Climax but not in case
<strong>of</strong> Meteor which yielded similar to I 1 and I 2 . The results also showed that
both cultivars produced more dry weight during the year 2006-07. These
results are in line with Vieira et al., (33) who reported a yield reducation <strong>of</strong>
35-41 percent when drought stress was imposed during seed filling. When
drought stress was imposed, significantly inferior quality seeds were
produced as compared to well watered control plants.
Seed yield per hectare (Tons)
On average basis seed, yield was maximum in case <strong>of</strong> Meteor (2.5 t) in
treatment I 3 while Climax performed better (2.2 t) in treatment I 4 . As far as
year effect is concerned, both cultivars produced more seed yield during the
year 2006-07 where Meteor excelled (2.3 t) the cultivar Climax (2.1 t). In
case <strong>of</strong> interaction, Meteor produced more seed yield (2.8 t) during 2006-07
in treatment I 3.
<strong>Irrigation</strong> at flowering and again at pod filling represented the traditional
irrigation recommendation for dry peas grown on heavier soils (28). The low
yields were associated with low number <strong>of</strong> pods, nodes per stem and pods
per node and a slower increase in pod weight (19). In these experiments,
irrigation at any growth stage increased yield but the highest yield for both
cultivars were achieved where water stress was completely eliminated by
irrigating upto seed filling stage where yield was significantly higher than
those achieved by other irrigation treatments.
Electrical conductivity (µ/g)
On the basis <strong>of</strong> two years average, maximum electrical conductivity was
found in both cultivars in I 3 (Meteor 23.4 and Climax 22.9 us/g) followed by
treatment I 2 (Meteor 22.6 and Climax 22.3 us/g) (Table 5). As far as years
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effect is concerned, both cultivars gave more electrical conductivity during
the year 2006-07 (Meteor 24.2 and Climax 23.9 us/g).
Seed yield and viability can be reduced by environmental stress. Little
information is available concerning the effect <strong>of</strong> environmental stress on
seed quality (30). Unfavourable environmental conditions during seed
development and maturation reduced viability and vigour. Environmental
stress during seed production can affect subsequently seed quality. Stress
occurring after physiological maturity, but before harvest can cause
reduction in soybean seed germination and vigour (30, 32, 33). Soybean
seeds that experienced hot and dry weather during maturation exhibited
reduced laboratory germination and field emergence. Severe drought that
occurred throughout seed filling reduced yield and seed number at a faster
rate than seed mass, germination or vigour and maintained the development
<strong>of</strong> some viable and vigorous seed. Nichols et al. (20) working with potted
pea plants observed no effect <strong>of</strong> drought stress on seed conductivity or
germination. Matthews and Bradnock (16) proposed the use <strong>of</strong> this test for
pea seeds and the procedure has been standardized by the Processors and
Growers Research Organization (P.G.R.O., 1981).
Seed germination (%)
Germination test showed that treatment I 4 excelled in seed germination in
case <strong>of</strong> both cultivars (Climax 96.1 and Meteor 94.5%) followed by I 2 (Climax
93.3 and Meteor 91.1%) (Table 5). For the years effect. seed germination
was better during the year 2005-06 (Climax 94.0 and Meteor 92.5%) as
compared to the year 2006-07 (Climax 93.2 and Meteor 90.2%).
Simiciklas et al. (26) mentioned that drought stress can lower seed quality
and germination <strong>of</strong> seeds <strong>of</strong> soybean if applied during various stages <strong>of</strong>
flowering and seed development. Stress occurring after physiological
maturity but before harvest can cause reduction in soybean seed
germination and vigour (8, 30, 32, 33). Heatherley (12) observed that
drought stress resulted in reduced germination <strong>of</strong> harvested soybean. The
results <strong>of</strong> germination were seedlings which may be normal or abnormal.
The percentage <strong>of</strong> normal, healthy and vigorous seedlings produced under
optimal conditions in the laboratory.
Emergence percentage
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Maximum emergence <strong>of</strong> seedlings was found in treatment I 3 (Climax 97.5%
and Meteor 93.0%) (Table 5). A field emergence percentage test gives
information about seed vigour and gives more accurate data to predict the
storability <strong>of</strong> seed lot tested. If the field conditions are optimal, the results
<strong>of</strong>
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emergence test usually correlate well with field emergence (1, 9, 29), but
under suboptimal field conditions, the laboratory germination results <strong>of</strong>tenly
in overestimating the actual field emergence <strong>of</strong> seed lots (14, 29, 36). There
can be considerable differences between the laboratory germination <strong>of</strong> a
seed lot and its emergence in the field.
CONCLUSION
From the results <strong>of</strong> two years investigations, it is concluded that cultivar
Meteor when irrigated upto seed filling (I 3 ) performed better than Climax
under Faisalabad conditions during both the years.
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