Evaluation of Girdle Sprinkler Irrigation System for Coconut in Intermediate and Dry Zone of Sri Lanka

Abstract

Irrigation has become an essential and important practice for coconut cultivation especially in Intermediate and Dry zones of Sri Lanka. Even though several methods have been recommended, none of those methods have been successfully practiced yet. The girdle sprinkler system is a new approach to overcome difficulties occurred in this sector. The objective of this study was to develop a suitable irrigation system for small scale coconut lands and to assess the best model through the study of field uniformity. The water distribution uniformity is the key parameter which was used to evaluate the system. The girdle sprinkler irrigation system was installed in 0.4 hectare (64 palms) block as half acre was installed with 16 mm conduit pipe laterals and other half acre was installed with 20 mm PVC pipe laterals. Several modifications such as leveling of girdle sprinklers, looping of laterals, testing with different pressure levels, shifting sub-main line to the middle of the field, testing with same girdle sprinkler were carried out in order to achieve the maximum distribution uniformity. Flow rates and pressure were measured to calculate the uniformity. A comparison was carried out with drip irrigation system to evaluate the system. The girdle sprinkler system which comprise with 1 kgcnr 2 inlet pressure with sub-mainline in middle modification having 20 mm PVC laterals has showed 94% distribution uniformity and the similar system with 16mm conduit laterals showed 91 % of distribution uniformity which shows an excellent distribution uniformity. Therefore this irrigation system is a viable method for small scale coconut cultivation. This method requires very less amount of technical support to install and maintain the system.

Full text

Evaluation
of
Girdle
Sprinkler
Irrigation
System
for
Coconut
in
Intermediate
and
Dry
Zone
of
Sri
Lanka
'L.R.M.C.
Liyanage,
2Y.
Purusothaman,
'D.P.
Panditharathna,
'N.A. Tennakoon
'^oz'/s
and
Plant
Nutrition
Division,
Coconut
Research Institute, Lunuwila
'•Faculty
of
Agriculture,
University
of
Jaffna,
Jaffna
ABSTRACT
Irrigation has become an essential and important practice for coconut cultivation especially in
Intermediate and Dry zones of Sri Lanka. Even though several methods have been recommended,
none of those methods have been successfully practiced yet. The girdle sprinkler system is a new
approach to overcome difficulties occurred in this sector. The objective of this
study
was to
develop a suitable irrigation system for small scale coconut lands and to assess the best model
through
the
study
of field uniformity. The water distribution uniformity is the key parameter which
was used to evaluate the system.
The
girdle sprinkler irrigation system was installed in 0.4 hectare (64 palms) block as
half
acre
was
installed with 16 mm conduit pipe laterals and other
half
acre was installed with 20 mm PVC pipe
laterals.
Several modifications such as leveling
of
girdle sprinklers, looping of
laterals,
testing with
different pressure levels, shifting sub-main line to the middle of the field, testing with same girdle
sprinkler were carried out in order to achieve the maximum distribution uniformity. Flow rates and
pressure were measured to calculate the uniformity. A comparison was carried out with
drip
irrigation
system
to evaluate the system.
The
girdle sprinkler system which comprise with 1 kgcnr2 inlet pressure with sub-mainline in
middle modification having 20 mm PVC laterals has showed 94% distribution uniformity and the
similar
system with 16mm conduit laterals showed
91
% of distribution uniformity which shows an
excellent
distribution uniformity. Therefore this irrigation system is a viable method for small scale
coconut
cultivation. This method requires very less amount of technical
support
to install and
maintain the system.
Key
words:
Flow
rate,
girdle
sprinkler,
irrigation,
uniformity
INTRODUCTION
Coconut
is one of the major plantation crops in Sri
Lanka,
covering about
395,000
hectare (Central
Bank
of Sri Lanka Annual Report,
2005)
and is
grown in different soil types having varying moisture
regimes (Somasiri et al.,
1994).
The potential extent
for
coconut cultivation is
687,194
ha and spreading
to different areas in coconut triangle and to
down
south of Sri Lanka (Tennakoon,
2005).
Coconut is
the most widespread plantation crop in Sri Lanka
occupying about 25% of national agricultural lands
(Perera,
1990).
From the total extent of coconut
lands 29%o is situated in the Dry zone while 51%
and 20% are distributed in the Intermediate and
Wet
zones respectively (Tennakoon,
2005).
In Sri
Lanka
majority of the coconut lands are situated in
coastal
areas (coastal plane) and river basins
(alluvial
plane). The surface layer of most soils in
coastal
planes and alluvial planes are sandy in
nature. The alluvial soils occurs in the mantled plane
is
also sandy up to
60cm
depth
(Somasiri et al,
1994).
Coconut
palm exhibits continuous concurrent
vegetative and reproductive phases and its

SECOND
SYMPOSIUM
ON
PLANTATION
CROP
RESEARCH
productivity is substantially influenced by
environmental variables.
Soil
moisture has been
identified
as a major factor with significant influence
on monthly variation of coconut yield, particularly
in areas where are subjected to long dry period or
where rainfall is low or poorly distributed (Somasiri
et al.; Vidhana Arachchi,
1998a).
Moisture stress
is
known to retard the growth
of
young palms, delay
the initiation of flowering, increase the button nut
shedding and immature nut
fall
and reduce the
number and size of the
nuts
in coconut palms
(Abeywardena,
1971).
It also directly trigger to all
physiological
functions of the palm such as C02
intake
(Taiz
and Zeiger,
1991).
Although coconut is presently grown throughout all
Agro-ecological
Regions of Sri Lanka, only few of
these environments are suitable for coconut in all
aspects.
Others show one or more adverse
effects
on its production particularly due to unfavorable soil
characteristics
and weather conditions (Somasiri
et al., 1994; Vidhana Archchi,
1998a).
The crop
water requirement for optimum growth is location
specific
and varies with climate,
soil,
variety/hybrid
and the system of irrigation. In Thamilnadu the
general irrigation recommendation is 100 liters/palm/
day with
drip
irrigation (Anone; 1999) and it is 32
liters/palm/day in west coast in Ivory Coast
(Nampoothiri and Singh,
2000).
The general
recommendation in Sri Lanka is 40 - 60 liters/palm/
day depending on the soil type (Vidhana Archchi,
1998b).
Coconut palm could absorb 28 - 46 liters
of
water in a dry day. The estimated transpiration
rate is 90 - 100 liters per palm in a dry day in the
dry period (Mohandas et al.,
1989).
Irrigation has a greater influence on coconut yield.
An
experiment conducted by Coconut Research
Institute revealed that there is a 49% yield increase
compared to none irrigated coconut land, when
coconut
land is irrigated with 40 liters/palm/day at
six
days intervals with
250g
of
adult
palm mixture
(APM.)
plus
83g
of
dolomite at monthly intervals in
the intermediate zone (Tennakoon et al.,
2005).
Even
with irrigation along shows 37% yield increase
compared to none irrigated coconut land
(Tennakoon,
2006).
Split
application of fertilizer is
possible
with an irrigation system which is known
as furtigation. In order to
fulfill
the above irrigation
requirement, several irrigation methods have been
practiced
by the growers. Drip irrigation, sprinkler
irrigation, hose irrigation are some of improved
methods and
drip
irrigation is the mostly practiced
and easily available improved method in the market
for
coconut. However many of the above systems
have shown various difficulties when used in the
field.
A diagnostic survey on agronomical practices
on coconut revealed that the
inefficiency
of present
irrigation systems and suggested more
efficient
method to be identified (Peiris et al.,
2006).
Irrigation uniformity is an important technical factor
in any irrigation system. Irrigation uniformity refers
to how the water is distributed uniformly in the
irrigated area in a given time or that the
depth
of
water application throughout the entire irrigated
area is about the same (Dorota et al.,
2005).
The
degree
of
uniformity however, can be highly variable
depending
upon
irrigation system and management.
The
girdle sprinkler irrigation system is a new
concept
which tries to solve some problems
prevailing in present irrigation systems. The primary
objective
of this
study
is to design and evaluate a
girdle sprinkler irrigation system for coconut small
holders in Sri Lanka.
MATERIALS
AND
METHODS
The
experiment was conducted at Rathmalagara
estate,
Madampe by the
Soils
and Plant Nutrition
Division,
Coconut Research Institute of Sri Lanka
(CRISL).
The experimental location has shallow
sandy
clay
loam soils belongs to
Andigama
soil
series
(Red
Yellow
Podsolic) which belong to the
land suitability class S4 based on the land suitability
classification
introduced by
CRISL.
0.4 hectare
square shape
block
of experimental plot was
selected
including 64 palms having 8m x 8m
spacing.
The slope of the selected site is 2.5%.
Two
materials were tested for laterals as 20 mm
PVC
pipes and 16 mm conduit pipes. Four laterals
358

A
NOVEL
METHOD
FOR
COCONUT
IRRIGATION
were installed as two laterals for each material.
Each
lateral was installed in the middle of two
coconut
rows. Sixteen delivery tubes (sub laterals)
were connected at either side and along the lateral
to deliver water to coconut palms. Girdle sprinklers
were connected to each delivery line and all the
system
was buried
under
one foot except girdle
sprinklers. Girdle sprinklers were made using 4mm
low
density poly ethylene
(LDPE)
tubes. First the
tube was circulated and tightened around the palm
and then; eight orifices having 1mm diameter were
drilled with 20 - 30° angle from the
trunk
keeping
equal distance between
orifices.
All laterals were
connected
to 1 inch sub main line and it was
connected
to 2 inches main line. A screen filter
made by using 0.5 mm stainless steel wire mesh
was also installed at the main line (Fig. 1 and 2).
Finally
the system was operated and initial
measurements were taken as flow rate and
pressure at each girdle sprinkler by using a water
meter and a pressure gauge. The system was
x -fr- 1 + 2 H
}-3-$-4+5-*-6-$-7-$-
1 II -' II . II II II.
~^ll
II
1
H
Y
+ i
y + \
i ii :
n
1 1 r
I
+ + + +
j + + + +
:
ll ii II ii,
1
1 1
1"1
i
HI
1 1 r
:+
+ + +
Conduit
laterals
Sub
laterals
Filter
Main
line
PVC
laterals
D
Coconut
palm
~Sub
main
in the
middle
+
+ + +
4=
+
+
+
+ + +
=f=
Fig.
1.
Field
layout of the
initial
girdle
sprinkler
irrigation
system
4
mm
LDPE
tube
Coconut
palm
Girdle sprinkler
Fig.
2. Schematic diagram of a
girdle
sprinkler at the
coconut
palm
359

SECOND
SYMPOSIUM
ON
PLANTATION
CROP RESEARCH
operated
under
two different pressure levels and
series
of modifications have been carried out as
leveling
of girdle sprinklers to one contour level,
looping of same laterals together, shifting the sub
main line to the middle of the field and measuring
all
points with one unique girdle in order to minimize
errors due to manufacturing defects of girdle
sprinklers. Flow rate and pressure were measured
after
each modification. Finally the system was
compared with existing
drip
irrigation system and
uniformity was calculated using distribution
uniformity (DU) equation developed by Peacock
at el,
(1998).
[DU = (average low quarter flow
rate / overall average flow rate) x
100%)]
RESULTS
AND DISCUSSION
Pressure
changes
analysis
Initial
pressure at each girdle sprinkler point is
shown in Fig. 3. Pressure reduction is higher in
conduit laterals
than
PVC laterals as from 1.6 kg
cnr2
to 0.95 kg cm2 and from 1.65 kg cm'2 to 1.35
kg cnr2 respectively. The operating pressure of the
system
is 1.75 kg cnr2
The
initial pressure is highly variable before
modifications
along the lateral in both conduit and
PVC
laterals. However in a particular point of a
lateral,
two girdle sprinklers those were connected
to that particular point through sub laterals show
almost
equal pressure values.
gjLateral
'X' A
^Lateral
'Y' A
Lateral
'X' B
iJLateral'Y' B
Pressure
variation under
each
modification
Pressure variation after leveling of girdle sprinklers
and looping of similar laterals are shown in Fig. 4.
Girdles
sprinklers at the beginning of each lateral
show the highest pressure values in each lateral
and decrease along the lateral towards the end.
This
is basically due to the friction loss inside the
tubing system. Initially the rate of the pressure loss
is
high and then the rate also decreases towards
the end of the lateral.
Since
there is a high pressure
at the beginning of the lateral the velocity of water
is
also high. When the velocity is high it increases
the friction loss. Therefore the rate of reduction of
pressure is also high at the beginning of the lateral.
Similarly
towards the end of the lateral the velocity
of
water is low due to low pressure. Therefore it
reduces the friction loss too and the rate of
reduction of pressure is also
less.
The
highest pressure for girdle sprinklers with
conduit laterals is 1.75 kgcm2and the lowest is 0.95
kgcnr2.
Leveling of girdle sprinklers eliminates the
variation
of
pressure due to the slope in the field. It
conserves
the pressure in the system. Pressure
reduction was further reduced by looping of ends
of
similar laterals together. The highest pressure
observed
at girdle sprinklers at PVC laterals was
1.75
kgcnr2 and the lowest pressures is
1.35
kgcnr2.
2 3 4 5 6
Pal m n u m ber
3 4 5 6 7
Palm
numbe
r
Fig.
3. The
pressure
variation at girdle
sprinklers
in 16 mm conduit (A and B) and
20mm
PVC
(C
and D) laterals.
360

A
NOVEL
METHOD FOR COCONUT
IRRIGATION
*
AX
initial
•
B 'X1
initial
A
AX levelled
•
BX levelled
*
AX looped
*
B 'X1 looped
O Avreage
Log.
(Avreage)
2 3 4 5 6 7 8
Palmnimber
2
1.8
1.6
I
1.4
I1
«
1.2
8
'
0.8
0.6
2 3 4 5 6 7
Palm
number
•
CXintiil
A
D'X
initial
"
CXlevelfed
*
D'X levelled
©
CX looped
H
D'X looped
Log.
(Average)
Fig.
4. Pressure
changes
along the conduit laterals (A'X\ B'X') and PVC laterals (CX', D'X')
under
higher
pressure
According
to the observed results 20 mm PVC
laterals
show better results than conduits.
Since
PVC
has higher diameter than conduits it has less friction
loss
arid due to that the pressure reduction is also
less.
Further, for conduits number of fittings and
connecters
used are higher than PVC. This also
affects
to reduce the pressure in conduits. However
20
mm PVC laterals are better than conduit lateral
for
this type of irrigation system.
Pressure change under lower operating
pressure
When
the girdle sprinkler system is operated
under
higher
pressure it creates mist and water get lost
by
wind. On the other hand if the water application
rate creates a surface runoff, flow rate should be
reduced. Therefore, the system was operated
under
lower
pressure as 1 kgem'2 and the results are
shown in Fig. 5.
Pressure reduction was reduced as from 1 kg cm"
2
to 0.7 kg enr2 at girdle sprinklers in conduit laterals
and from 1 kg cm2 to 0.8 kg cm'2 at girdle sprinklers
in
PVC laterals. The percentages of pressure
changes
in conduit laterals and PVC laterals are
30%
and 20% respectively. This result indicates
that the operation of girdle sprinklers
under
lower
pressure increases the accuracy of water
application.
~0- Lateral A
-*"~
Lateral B
Jk-
Lateral C
~~0—
Lateral D
Palm
number
Fig.
5.
Pressure change along
the
laterals
under
lower pressure
A, B -
Conduit
laterals
C, D - PVC
laterals
361

SECOND
SYMPOSIUM
ON
PLANTATION
CROP
RESEARCH
Pressure
change
analysis
with sub mainline
in
the middle of the system
When
the sub mainline is shifted to the middle of
the irrigated field the length
of
all
laterals are reduced
by
half
of the initial length. The system was
operated under 0.99 kgcnr2 mainline pressure.
Results
are shown in Fig. 6.
from
0.99 kg cnr2 to 0.89 kg cnr2 which show just
10.1%
reduction. Girdle sprinkles at PVC laterals
shows pressure reduction from 0.95 kg cnr2 to 0.90
kg cnr2 which
is
just 5% reduction.
Still
PVC laterals
give
better results than conduits laterals.
•
Lateral
A
x
Lateral
AA
•
Lateral
BB
Log.
(Average)
1 2 3
Palm
number
0
12 3
Palm
number
°
Lateral
C
*
Lateral
D
*
Lateral
CC
*
Lateral
DD
Log.
(Average)
Fig.
6. Pressure change along the 16mm conduit laterals and 20 mm PVC laterals
under
lower
pressure
Lateral
A
Lateral
B
1 2 3 4 5 6 7
Palm
number
12
3 4 5 6 7
Palm
number
Fig.7.
Flow rate variation along the 16mm conduit laterals (a) and
20mm
PVC laterals (b) at the
initial
modification
The
pressure reduction was further reduced
towards the end in both lateral types. This system
increases
the uniformity of water application.
Further the maintenance of the system would be
much easier with laterals with short length. Pressure
changes
in girdle sprinklers at conduit laterals is
Flow
rate
changes
analysis
Flow
rate is the most important parameter for any
type of micro irrigation system. It determines the
application uniformity of system and the total time
required for one irrigation
cycle
too. The flow rate
362

A
NOVEL
METHOD
FOR
COCONUT
IRRIGATION
should be related with the soil characteristics in
order to minimize water losses
through
surface and
subsurface runoff and evaporation. Initial flow rates
at each girdle sprinklers in the whole system shows
very high.'variation as shown in Fig. 7.
Girdle
sprinklers with 16mm conduit laterals show
68.23
liters/hour average flow rate varying between
79.69
liters/hour and 51.80 liters/hour when
operated'under 1.65 kg/cm2 mainline pressure.
Similarly
girdle sprinklers at 20mm PVC laterals
show 76-81 liters/hour averaged flow rate. It also
varied between
101.41
liters/hour and 39 liters/hour
this variation is basically due to the pressure losses
along the laterals,
undulating
pattern
of
the land prior
Girdle
sprinkler system operated
under
1.6 kg
cm2mainline
pressure causes mist formation and
it
creates fairly higher variation of flow rates
between girdle sprinklers. It also makes surface
runoff
and subsurface runoff when the flow rate is
higher
than
that of infiltration rate. Therefore, the
maximum application flow rate
depends
on the
infiltration
rate of the
soil.
In
order to prevent above losses the system was
operated
under
lower pressure as 1 kg cnr2 and
results are shown in Fig. 9.
fcateraPA
2
3 4 5
Palm
number
tater-al-C
2
3 4 5
Palm
number
Fig.8.
Flow
rate variation
along
the 16mm conduit laterals (A, B) and
20mm
PVC laterals (C,
D)
after
leveling
of
girdle
sprinklers
to leveling
of
girdle sprinklers. Further the variation
of
diameters in
orifices
of girdle sprinklers also
increases
the flow rate variation.
Leveling
of girdle sprinklers and looping
of
similar
laterals together show a significant reduction of flow
rate variation. It increases the application uniformity
further.
Flowlrate
changes after leveling
of
girdle sprinklers
and looping of laterals are shown in Fig. 8. Mean
flowirate
at each lateral system was increased due
to the conservation of pressure inside the system.
Leveling
of girdle sprinklers for a particular height
solves
the slope
effect
to the system.
Flow
rate variation
under
lower
pressure
Flow
rate variation was reduced up to 33% in girdle
sprinklers at 16 mm conduit laterals and up to 21%
in girdle sprinklers at 20 mm PVC laterals. Girdle
sprinklers with PVC laterals show better uniformity
than
conduit laterals. However the present flow
variation within a particular lateral is due to the
pressure reduction and due to the variation
of
orifice
diameters in girdle sprinklers. Therefore a. proper
mechanism
should be developed to
prepare
girdle
sprinkler
orifices
with
exact
dimensions.
363

SECOND
SYMPOSIUM
ON
PLANTATION
CROP RESEARCH
Lateral
A
Lateral
B
1 2 3 4 5 6 7 8
Palm number
80
|70
•S
.2*60
rt
ta40
30
Lateral-G-
Lateral
D
2
3 4 5 6 7
Palm
number
Fig.9.
Flow rate change along the 16mm conduit laterals (A, B) and the
20mm
PVC laterals (C,
D)
under
lower
pressure
Flow
rate variation with the sub main in the
middle
of the system
Once
the sub mainline is shifted to the middle of
the system the whole uniformity of the water
application is increased with mean flow rates for
PVC
system and conduit system showing
66.86
liters/hour and
68.95
liters/hour respectively. Results
are shown in Fig. 10. Maximum flow rate difference
for
girdle sprinklers with conduit laterals is 13.46
liters/hour and it is 9.42 liters/hour for girdle
sprinklers with PVC laterals.
However even after a series of modifications still
the system shows some variation in the application
of
water. This is basically due to the errors in girdle
sprinklers made in the laboratory
scale.
Results from
the unique girdle sprinkler shows the best result as
shown in Tables 1 and 2. Manufacturing defects
were over come by this modification. The maximum
flow
rate difference for conduits is 5.98 liters/hour
while the mean flow rate is 96.14 liters/hour. The
highest accuracy was achieved with this
modification
since all orifices have exact 1mm
diameter. On the other hand girdle sprinklers with
PVC
laterals show 5.26 liters/hour flow rate
variation from 100 liters/hour to
94.74
liters/hour.
The
mean flow rate is
96.87
liters/hour.
'Lateral
"A"
'Lateral"AA"
'
Lateral
"B"
'
Lateral
"BB"
2 3
palm
numbe
r
Lateral
"C" -o- Lateral"D"
Lateral
"CC" Lateral "DD"
Fig.
10.
Flow rate
changes
along the 16mm conduit laterals (A,B,AA,BB) and
20mm
PVC laterals
(CD.CC.DD)
when
the sub
main
line in the
middle
364

A
NOVEL
METHOD
FOR
COCONUT
IRRIGATION
Table
1. Flow rate variation along the 16 mm conduit laterals
with
a unique girdle sprinkler
Palm Lateral A Lateral B Lateral
AA
Lateral BB
Number
(lit/hr) (lit/hr)
(lit/hr)
(lit/hr)
!•
1
99.08 98.18 99.08 98.18
;
2
96.43
94.74
97.30 97.30
;
3
95.58
93.10
94.74
96.43
1 4
94.74
93.10
96.43
93.91
Table 2. \Flow rate variation along the
20 mm PVC laterals
with
a uni que girdle sprinkler
\
Palm Lateral C Lateral D Lateral CC Lateral DD
I
number
(lit/hr) (lit/hr)
__
(lit/hr) (lit/hr)
\
1
97.30
98.18
96.4.3
100.00
:
2
97.30
96.43 96.43 96.43
;
3
97.30 97.30
94.74
96.43
•
4
97.30
95.58
96.43 96.43
Water
distribution uniformity
The
Table 3 shows that the percentage of
uniformity values
of
different
modifications
of
girdle
sprinkler irrigation system with different diameters
of
lateral and
drip
irrigation system. According to
the water distribution uniformity rating
(Peacock
and Handley.,
1998),
the girdle sprinkler irrigation
system
with
16
mm conduit laterals, the sub-mainline
in middle modification is an excellent system for
irrigation of
coconut.
The uniformity value for this
system
is 91%. Similarly after leveling of girdle
sprinklers, after looping laterals, operated with low
pressure water
pump
and sub-mainline in middle
modifications
of
20mm
PVC laterals girdle sprinkler
irrigation systems are excellent systems (Those
values are 91 %,
91
%, 90% and 94% respectively).
The
girdle sprinkler irrigation system with 20 mm
PVC
laterals gives much uniformity of water
distribution to the irrigated area than 16mm conduit
laterals girdle sprinkler irrigation system. Because
of
the pressure losses is less in the 20mm PVC
laterals girdle sprinkler irrigation system.
Table
3. The uniformity
values
(%) relevant to
each
modifications of girdle sprinkler irrigation
system
and comparison
with
drip irrigation
system
Type
of
Before
After After
With
1"
Sub-main
With
Drip
lateral
leveling leveling
looping
pump
in middle
same
irrigation
girdle
system
,16mm
Conduit
83
86
88
89
91
97 87
J20mm
JPVC
75
91 91
-
90
94
98
365

SECOND
SYMPOSIUM
ON
PLANTATION
CROP RESEARCH
CONCLUSION
The
results obtained
on
PVC laterals
and
conduit
laterals show that PVC laterals, which
has 20 mm
diameter
are
better
than
conduit laterals which
has
16
mm
diameter
for
girdle sprinkler irrigation
The
girdle sprinkler system, which comprise
one
kg cnr2 inlet pressure with sub-mainline
in
middle
of
the field, having
20 mm
PVC laterals
has 94 %
of
distribution uniformity.
The
same system- with
16
mm
conduit laterals
had
91%
of
distribution
uniformity. Therefore, this irrigation system
is a
viable
method
for
small scale coconut cultivation.
The
distribution uniformity
of
the girdle sprinkler
irrigation system
can be
further increased
by
producing girdle sprinklers with
standard
levels.
This
system conserves water
as
well
as
labour
compared
to
hose irrigation.
It
also has less clogging
incidence
compared
to
drip
irrigation
so
that even
harvested rain water
or
water with silt
parts
can
be
used
to
irrigate with just
a
screen filter.
The
total cost
for
one acre girdle sprinkler irrigation
system with
PVC
laterals
is Rs:
32,800.00
compaired
to
Rs:
31,000.00
with conduit laterals
(excluding
the
water pump).
ACKNOWLEDGEMENTS
Authors wish
to
thank
all the
staff
of the
Soils
and
Plan Nutrition Division
of the
Coconut Research
Institute
for
their invaluable
support
in
conducting
this research successfully.
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A
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