pressure were measured to calculate the uniformity. A comparison was carried out with drip irrigation system to evaluate the system. The girdle sprinkler system ...
Evaluation of Girdle Sprinkler Irrigation System for Coconut in Intermediate and Dry Zone of Sri Lanka 2
'L.R.M.C. Liyanage, Y. Purusothaman, 'D.P. Panditharathna, 'N.A. Tennakoon '^oz'/s and Plant Nutrition Division, Coconut Research Institute, '•Faculty of Agriculture,
Lunuwila
University of Jaffna, Jaffna
ABSTRACT Irrigation has become an essential and important practice for coconut cultivation especially in Intermediate and Dry zones o f Sri Lanka. Even though several methods have been recommended, none o f those methods have been successfully practiced yet. The girdle sprinkler system is a new approach to overcome difficulties occurred in this sector. The objective o f this study was to develop a suitable irrigation system for small scale coconut lands and to assess the best model through the study o f 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 P V C pipe laterals. Several modifications such as leveling o f girdle sprinklers, looping o f laterals, testing with different pressure levels, shifting sub-main line to the middle o f 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 k g c n r
2
inlet pressure with sub-mainline in
middle modification having 20 mm PVC laterals has showed 9 4 % distribution uniformity and the similar system with 16mm conduit laterals showed 91 % o f 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 o f technical support to install and maintain the system.
Key words: Flow rate, girdle sprinkler, irrigation, uniformity
INTRODUCTION
lands 29%o is situated in the Dry z o n e while 5 1 % and 2 0 % are distributed in the Intermediate and
C o c o n u t is o n e o f the m a j o r plantation crops in Sri
Wet z o n e s r e s p e c t i v e l y ( T e n n a k o o n , 2 0 0 5 ) . In Sri
L a n k a , c o v e r i n g about 3 9 5 , 0 0 0 h e c t a r e (Central
L a n k a m a j o r i t y o f the c o c o n u t lands are situated in
B a n k o f Sri L a n k a A n n u a l R e p o r t , 2 0 0 5 ) and is
coastal areas ( c o a s t a l p l a n e ) and river basins
grown in different soil types having varying moisture
(alluvial p l a n e ) . T h e surface layer o f m o s t soils in
regimes ( S o m a s i r i et al., 1 9 9 4 ) . T h e potential extent
c o a s t a l p l a n e s and alluvial planes are sandy in
for coconut cultivation is 6 8 7 , 1 9 4 ha and spreading
nature. T h e alluvial soils occurs in the mantled plane
to different areas in c o c o n u t triangle and to down
is also sandy up to 6 0 c m depth ( S o m a s i r i et
south o f Sri L a n k a ( T e n n a k o o n , 2 0 0 5 ) . C o c o n u t is
1994).
al,
the most widespread plantation crop in Sri L a n k a occupying about 2 5 % o f national agricultural lands
Coconut palm exhibits continuous
(Perera, 1 9 9 0 ) . F r o m the total extent o f c o c o n u t
v e g e t a t i v e and r e p r o d u c t i v e
concurrent
p h a s e s and
its
SECOND SYMPOSIUM ON PLANTATION CROP RESEARCH
is s u b s t a n t i a l l y i n f l u e n c e d b y
(Tennakoon, 2 0 0 6 ) . Split application o f fertilizer is
environmental variables. S o i l moisture has been
p o s s i b l e with an irrigation s y s t e m which is known
identified as a major factor with significant influence
as furtigation. In order to fulfill the above irrigation
on monthly variation o f c o c o n u t yield, particularly
requirement, several irrigation methods have been
productivity
in areas w h e r e are s u b j e c t e d to long dry period or
practiced by the g r o w e r s . Drip irrigation, sprinkler
where rainfall is low or poorly distributed (Somasiri
irrigation, hose irrigation are s o m e o f improved
et al.; Vidhana A r a c h c h i , 1 9 9 8 a ) . M o i s t u r e stress
methods and drip irrigation is the mostly practiced
is known to retard the growth o f young palms, delay
and easily available improved method in the market
the initiation o f flowering, i n c r e a s e the button nut
for c o c o n u t . H o w e v e r m a n y o f the a b o v e s y s t e m s
shedding and i m m a t u r e nut fall and r e d u c e the
have shown various difficulties when used in the
n u m b e r and s i z e o f the nuts in c o c o n u t p a l m s
field. A diagnostic survey on agronomical practices
( A b e y w a r d e n a , 1 9 7 1 ) . It also directly trigger to all
on coconut revealed that the inefficiency o f present
physiological functions o f the p a l m such as C 0
irrigation s y s t e m s and s u g g e s t e d m o r e efficient
2
intake (Taiz and Z e i g e r , 1 9 9 1 ) .
method to b e identified ( P e i r i s et al., 2 0 0 6 ) .
Although coconut is presently grown throughout all
Irrigation uniformity is an important technical factor
A g r o - e c o l o g i c a l R e g i o n s o f Sri L a n k a , only few o f
in any irrigation system. Irrigation uniformity refers
these environments are suitable for c o c o n u t in all
to how the water is distributed uniformly in the
aspects. Others s h o w o n e or m o r e adverse effects
irrigated area in a given time or that the depth o f
on its production particularly due to unfavorable soil
water application throughout the entire irrigated
characteristics and w e a t h e r c o n d i t i o n s ( S o m a s i r i
area is about the s a m e ( D o r o t a et al., 2 0 0 5 ) . T h e
et al., 1 9 9 4 ; V i d h a n a A r c h c h i , 1 9 9 8 a ) . T h e crop
degree o f uniformity however, can be highly variable
water requirement for o p t i m u m growth is location
depending upon irrigation system and management.
specific and varies with climate, soil, variety/hybrid and the s y s t e m o f irrigation. In T h a m i l n a d u the general irrigation recommendation is 100 liters/palm/ day with drip irrigation ( A n o n e ; 1 9 9 9 ) and it is 3 2 l i t e r s / p a l m / d a y in w e s t c o a s t in I v o r y C o a s t ( N a m p o o t h i r i and S i n g h , 2 0 0 0 ) . T h e g e n e r a l recommendation in Sri L a n k a is 4 0 - 6 0 liters/palm/
T h e girdle sprinkler irrigation s y s t e m is a n e w c o n c e p t w h i c h t r i e s to s o l v e s o m e p r o b l e m s prevailing in present irrigation systems. T h e primary o b j e c t i v e o f this study is to design and evaluate a girdle sprinkler irrigation system for c o c o n u t small holders in Sri L a n k a .
day depending on the soil type ( V i d h a n a A r c h c h i , 1 9 9 8 b ) . C o c o n u t palm could a b s o r b 2 8 - 4 6 liters
MATERIALS AND METHODS
o f water in a dry day. T h e estimated transpiration rate is 9 0 - 1 0 0 liters per p a l m in a dry day in the
T h e e x p e r i m e n t was c o n d u c t e d at R a t h m a l a g a r a
dry period ( M o h a n d a s et al., 1 9 8 9 ) .
estate, M a d a m p e by the S o i l s and Plant Nutrition Division, C o c o n u t R e s e a r c h Institute o f Sri L a n k a
Irrigation has a greater influence on c o c o n u t yield. An e x p e r i m e n t c o n d u c t e d b y C o c o n u t R e s e a r c h Institute revealed that there is a 4 9 % yield increase c o m p a r e d to none irrigated c o c o n u t land, when c o c o n u t land is irrigated with 4 0 liters/palm/day at six days intervals with 2 5 0 g o f adult palm mixture (APM.) plus 8 3 g o f d o l o m i t e at monthly intervals in the intermediate z o n e ( T e n n a k o o n et al.,
( C R I S L ) . T h e e x p e r i m e n t a l location has shallow sandy c l a y l o a m soils b e l o n g s to Andigama soil series ( R e d Y e l l o w P o d s o l i c ) w h i c h b e l o n g to the land suitability class S based on the land suitability 4
classification introduced by C R I S L . 0 . 4 hectare square shape b l o c k o f e x p e r i m e n t a l plot was selected including 6 4 palms having 8m x 8m spacing. T h e slope o f the s e l e c t e d site is 2 . 5 % .
2005).
Even with irrigation along shows 3 7 % yield increase
Two materials were tested for laterals as 2 0 m m
compared
P V C pipes and 16 m m conduit pipes. F o u r laterals
358
to
none
irrigated
coconut
land
A NOVEL METHOD FOR COCONUT IRRIGATION
were installed as two laterals for e a c h material.
drilled with 2 0 - 3 0 ° angle from the trunk k e e p i n g
E a c h lateral w a s installed in the middle o f two
equal distance b e t w e e n orifices. All laterals were
coconut rows. S i x t e e n d e l i v e r y tubes (sub laterals)
c o n n e c t e d to 1 i n c h s u b m a i n line and it w a s
w e r e c o n n e c t e d at either side and along the lateral
c o n n e c t e d to 2 i n c h e s main line. A screen filter
to deliver water to c o c o n u t palms. Girdle sprinklers
made by using 0.5 m m stainless steel wire m e s h
were c o n n e c t e d to e a c h d e l i v e r y line and all the
was also installed at the m a i n line ( F i g . 1 and 2 ) .
system was buried under o n e foot e x c e p t girdle sprinklers. Girdle sprinklers were m a d e using 4 m m
F i n a l l y the s y s t e m w a s o p e r a t e d and initial
low density p o l y e t h y l e n e ( L D P E ) tubes. First the
m e a s u r e m e n t s w e r e t a k e n as f l o w r a t e
tube was circulated and tightened around the palm
pressure at e a c h girdle sprinkler by using a water
and then; eight o r i f i c e s h a v i n g 1 m m diameter were
m e t e r and a p r e s s u r e g a u g e . T h e s y s t e m w a s
x
-fr-
1
+
2 H} 1
3 - $ - 4 + 5 - * - 6 - $ - 7 - $ -
II
1
Conduit
Y y
laterals Sub laterals
Filter
~^ll 1
II
1
-'
II .
Hn +
i
I+
+ \ j+
11i " 1 ii
:
i
:
HIll
+
+
+
4=
II
II
II.
1
1
r
+ +
+ +
+ +
ii 1
: +~Sub Main line
and
+ main
in the
II 1
ii,
r
+ middle +
+
+
PVC laterals
+
D Coconut palm
+
+
=f=
+ +
F i g . 1. Field layout of the initial girdle sprinkler irrigation system
Coconut palm 4 mm LDPE tube
Girdle sprinkler
F i g . 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
Pressure variation under each modification
series o f m o d i f i c a t i o n s h a v e b e e n carried out as leveling o f girdle sprinklers to o n e contour level,
Pressure variation after leveling o f girdle sprinklers
looping o f s a m e laterals together, shifting the sub
and looping o f similar laterals are shown in Fig. 4 .
main line to the middle o f the field and measuring
Girdles sprinklers at the b e g i n n i n g o f e a c h lateral
all points with one unique girdle in order to minimize
show the highest pressure values in each lateral
e r r o r s due to m a n u f a c t u r i n g d e f e c t s o f g i r d l e
and d e c r e a s e a l o n g the lateral towards the end.
sprinklers. F l o w rate and pressure w e r e measured
T h i s is b a s i c a l l y due to the friction loss inside the
after e a c h m o d i f i c a t i o n . F i n a l l y the s y s t e m w a s
tubing system. Initially the rate o f the pressure loss
c o m p a r e d with e x i s t i n g drip irrigation s y s t e m and
is high and then the rate also d e c r e a s e s towards
uniformity was calculated using
distribution
the end o f the lateral. S i n c e there is a high pressure
uniformity ( D U ) equation developed b y P e a c o c k
at the b e g i n n i n g o f the lateral the v e l o c i t y o f water
at el,
is also high. W h e n the v e l o c i t y is high it increases
( 1 9 9 8 ) . [ D U = ( a v e r a g e low quarter flow
the friction loss. T h e r e f o r e the rate o f reduction o f
rate / overall average flow rate) x 1 0 0 % ) ]
pressure is also high at the b e g i n n i n g o f the lateral.
RESULTS AND DISCUSSION
Similarly towards the end o f the lateral the velocity o f water is low due to low pressure. T h e r e f o r e it r e d u c e s the friction loss too and the rate o f
Pressure changes analysis
reduction o f pressure is also less. Initial pressure at e a c h girdle sprinkler point is shown in Fig. 3 . Pressure reduction is higher in
T h e h i g h e s t p r e s s u r e for girdle sprinklers with 2
conduit laterals than P V C laterals as from 1.6 k g
conduit laterals is 1.75 k g c m a n d the lowest is 0 . 9 5 2
2
2
2
c n r to 0 . 9 5 kg c m and from 1.65 kg c m ' to 1.35 2
k g c n r respectively. T h e operating pressure o f the system is 1.75 kg c n r
k g c n r . L e v e l i n g o f girdle sprinklers eliminates the variation o f pressure due to the s l o p e in the field. It c o n s e r v e s the p r e s s u r e in the s y s t e m . P r e s s u r e
2
reduction was further reduced by looping o f ends T h e initial p r e s s u r e is h i g h l y v a r i a b l e b e f o r e
o f similar laterals together. T h e highest pressure
modifications along the lateral in both conduit and
observed at girdle sprinklers at P V C laterals was
P V C laterals. H o w e v e r in a particular point o f a
1.75
kgcnr
2
and
the
lowest
pressures
is
2
lateral, two girdle sprinklers those w e r e c o n n e c t e d
1.35 k g c n r .
to that particular point through sub laterals show almost equal pressure v a l u e s .
gjLateral 'X' A ^Lateral 'Y'A Lateral ' X ' B iJLateral'Y' B
2
3 Pal
4 m
5 n u m
6 ber
3
4
5
6
7
P a m l n u m b e 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
2 *
A X initial
•
B ' X initial
1.8
A
A X levelled
1.6
1
•
B X
levelled
*
A X looped
I I
1.4 1
*
B ' X looped
«
O
Avreage
8 '
1
Log.
•
CXintiil
A
D ' X initial
"
CXlevelfed
*
D ' X levelled
©
C X looped
H
D ' X looped
1.2 Log. ( A v e r a g e )
0.8
(Avreage)
0.6 2
3 4 5 6 Palmnimber
7
2
8
F i g . 4. Pressure changes along the conduit laterals (A'X\ under higher pressure
3 4 5 6 Palm number
7
B'X') and PVC laterals (CX',
D'X')
A c c o r d i n g to the o b s e r v e d results 2 0 m m P V C
rate c r e a t e s a surface runoff, flow rate should b e
laterals show better results than conduits. S i n c e P V C
reduced. T h e r e f o r e , the system was operated under
has higher diameter than conduits it has less friction
l o w e r p r e s s u r e as 1 k g e m '
loss arid due to that the pressure reduction is also
shown in Fig. 5.
2
and the results are
less. Further, for conduits n u m b e r o f fittings and c o n n e c t e r s used are h i g h e r than P V C . T h i s also
Pressure reduction w a s reduced as from 1 k g cm" 2
affects to reduce the pressure in conduits. H o w e v e r
2
to 0.7 kg e n r at girdle sprinklers in conduit laterals 2
2 0 m m P V C laterals are better than conduit lateral
2
and from 1 kg c m to 0 . 8 kg c m ' at girdle sprinklers in P V C l a t e r a l s . T h e p e r c e n t a g e s o f p r e s s u r e
for this type o f irrigation s y s t e m .
c h a n g e s in conduit laterals and P V C laterals are Pressure
change
under
lower
operating
3 0 % and 2 0 % respectively. T h i s result indicates that the operation o f girdle sprinklers under l o w e r
pressure
pressure W h e n the girdle sprinkler s y s t e m is operated under
i n c r e a s e s the
accuracy of
water
application.
higher pressure it c r e a t e s m i s t and water get lost by wind. O n the other hand i f the water application
~0-
Lateral A
- * " ~ Lateral B -
J k Lateral C ~~
0 —
Lateral D
Palm number F i g . 5. Pressure laterals
change
along
the laterals
under lower pressure
A, B - Conduit laterals C, D - PVC
361
SECOND SYMPOSIUM ON PLANTATION CROP RESEARCH
Pressure change analysis with sub mainline in the middle of the system
2
from 0 . 9 9 kg c n r to 0 . 8 9 kg c n r
2
w h i c h show j u s t
1 0 . 1 % reduction. G i r d l e sprinkles at P V C laterals 2
shows pressure reduction from 0 . 9 5 kg c n r to 0 . 9 0 W h e n the sub m a i n l i n e is shifted to the middle o f
kg c n r which is j u s t 5 % reduction. Still P V C laterals
the irrigated field the length o f all laterals are reduced
give better results than conduits laterals.
2
b y h a l f o f the i n i t i a l l e n g t h . T h e s y s t e m w a s 2
o p e r a t e d under 0 . 9 9 k g c n r m a i n l i n e p r e s s u r e . Results are shown in F i g . 6.
•
Lateral A
x
•
°
Lateral C
*
Lateral D
Lateral A A
*
Lateral C C
Lateral B B
*
Lateral DD Log.
Log.
(Average)
(Average)
0
1 2 3 Palm number
1 2 3 Palm number
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
1 2
Palm number
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 T h e pressure reduction was further
reduced
Flow rate changes analysis
towards the end in both lateral types. T h i s system i n c r e a s e s the u n i f o r m i t y o f w a t e r a p p l i c a t i o n .
F l o w rate is the m o s t important parameter for any
Further the m a i n t e n a n c e o f the s y s t e m would b e
type o f m i c r o irrigation s y s t e m . It determines the
much easier with laterals with short length. Pressure
application uniformity o f s y s t e m and the total time
c h a n g e s in girdle sprinklers at conduit laterals is
required for o n e irrigation c y c l e too. T h e flow rate
362
A NOVEL METHOD FOR COCONUT IRRIGATION
should b e related with the soil c h a r a c t e r i s t i c s in
G i r d l e s p r i n k l e r s y s t e m o p e r a t e d under 1.6 kg
order to m i n i m i z e water l o s s e s through surface and
c m m a i n l i n e pressure c a u s e s mist formation and
subsurface runoff and evaporation. Initial flow rates
it c r e a t e s f a i r l y h i g h e r v a r i a t i o n o f f l o w r a t e s
at each girdle sprinklers in the w h o l e s y s t e m shows
b e t w e e n girdle sprinklers. It also m a k e s surface
very high.'variation as s h o w n in F i g . 7.
r u n o f f and s u b s u r f a c e r u n o f f when the flow rate is
Girdle sprinklers with 1 6 m m conduit laterals s h o w
m a x i m u m a p p l i c a t i o n flow rate depends on the
6 8 . 2 3 liters/hour a v e r a g e flow rate varying between
infiltration rate o f the soil.
2
higher than that o f infiltration rate. T h e r e f o r e , the
7 9 . 6 9 liters/hour and 5 1 . 8 0 liters/hour operated'under
1.65 k g / c m
2
when
mainline pressure.
In order to prevent a b o v e l o s s e s the s y s t e m was
S i m i l a r l y girdle sprinklers at 2 0 m m P V C laterals
operated under l o w e r pressure as 1 kg c n r
show 7 6 - 8 1 liters/hour a v e r a g e d flow rate. It also
results are s h o w n in F i g . 9 .
2
and
varied between 1 0 1 . 4 1 liters/hour and 3 9 liters/hour this variation is b a s i c a l l y due to the pressure losses along the laterals, undulating pattern o f the land prior
tater-al-C
fcateraPA
2
Fig.8.
3 4 5 Palm number
2
3 4 5 P a l m number
Flow rate variation along the 16mm conduit laterals (A, B) and 20mm PVC laterals (C, D) after leveling of girdle sprinklers
to leveling o f girdle sprinklers. Further the variation
Flow rate variation under lower pressure
o f diameters in o r i f i c e s o f girdle sprinklers also increases the flow rate variation.
F l o w rate variation w a s reduced up to 3 3 % in girdle sprinklers at 16 m m conduit laterals and up to 2 1 %
Leveling o f girdle sprinklers and looping o f similar
in girdle sprinklers at 2 0 m m P V C laterals. G i r d l e
laterals together show a significant reduction o f flow
sprinklers with P V C laterals show better uniformity
rate variation. It increases the application uniformity
than conduit laterals. H o w e v e r the present flow
further.
variation within a particular lateral is due to the pressure reduction and due to the variation o f orifice
Flowlrate c h a n g e s after leveling o f girdle sprinklers and looping o f laterals are s h o w n in F i g . 8. M e a n flowirate at e a c h lateral s y s t e m w a s increased due
diameters in girdle sprinklers. T h e r e f o r e a. proper m e c h a n i s m should b e developed to prepare girdle sprinkler orifices with e x a c t d i m e n s i o n s .
to the c o n s e r v a t i o n o f pressure inside the system. L e v e l i n g o f girdle sprinklers for a particular height s o l v e s the slope effect to the s y s t e m .
363
SECOND SYMPOSIUM ON PLANTATION CROP RESEARCH
Lateral A Lateral B
80
Lateral-GLateral D
|70 •S .2*60
rt ta40 30 1
2
3
4
5
6
7
2
8
3
4
5
6
7
Palm number
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
o f water. T h i s is b a s i c a l l y due to the errors in girdle sprinklers made in the laboratory scale. Results from
middle of the system
the unique girdle sprinkler s h o w s the best result as O n c e the sub m a i n l i n e is shifted to the middle o f
shown in T a b l e s 1 and 2 . M a n u f a c t u r i n g defects
the s y s t e m the w h o l e u n i f o r m i t y o f the w a t e r
were over c o m e by this modification. T h e m a x i m u m
application is i n c r e a s e d with m e a n flow rates for
flow rate difference for conduits is 5 . 9 8 liters/hour
P V C system and conduit s y s t e m s h o w i n g 6 6 . 8 6
while the m e a n flow rate is 9 6 . 1 4 liters/hour. T h e
liters/hour and 6 8 . 9 5 liters/hour respectively. Results
highest
are shown in Fig. 10. M a x i m u m flow rate difference
m o d i f i c a t i o n s i n c e all o r i f i c e s h a v e e x a c t 1 m m
for girdle sprinklers with conduit laterals is 1 3 . 4 6
diameter. On the other hand girdle sprinklers with
l i t e r s / h o u r and it is 9 . 4 2 l i t e r s / h o u r for g i r d l e
P V C l a t e r a l s s h o w 5 . 2 6 l i t e r s / h o u r f l o w rate
sprinklers with P V C laterals.
variation from 1 0 0 liters/hour to 9 4 . 7 4 liters/hour.
accuracy
was
achieved
with
this
T h e m e a n flow rate is 9 6 . 8 7 liters/hour. H o w e v e r even after a series o f modifications still the system s h o w s s o m e variation in the application
2
3
palm numbe r ' L a t e r a l "A"
' Lateral " B "
'Lateral"AA"
' Lateral " B B "
Lateral "C" - o - L a t e r a l " 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 A A
Lateral B B
Number
(lit/hr)
(lit/hr)
(lit/hr)
(lit/hr)
!• 1 ; ;
1
2
3
4
99.08
98.18
99.08
98.18
96.43
94.74
97.30
97.30
95.58
93.10
94.74
96.43
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
I number
Lateral D
(lit/hr)
Lateral C C
Lateral D D
(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
irrigation s y s t e m s are e x c e l l e n t s y s t e m s ( T h o s e values are 91 % , 91 % , 9 0 % and 9 4 % r e s p e c t i v e l y ) .
The Table 3
s h o w s that the p e r c e n t a g e o f
uniformity values o f different modifications o f girdle
T h e girdle sprinkler irrigation s y s t e m with 2 0 m m
sprinkler irrigation s y s t e m with different diameters
P V C laterals gives much uniformity o f water
o f lateral and drip irrigation s y s t e m . A c c o r d i n g to
distribution to the irrigated area than 1 6 m m conduit
the water distribution uniformity rating ( P e a c o c k
laterals girdle sprinkler irrigation s y s t e m . B e c a u s e
and Handley., 1 9 9 8 ) , the girdle sprinkler irrigation
o f the pressure l o s s e s is less in the 2 0 m m P V C
system with 16 m m conduit laterals, the sub-mainline
laterals girdle sprinkler irrigation system.
in middle m o d i f i c a t i o n is an e x c e l l e n t s y s t e m for irrigation o f c o c o n u t . T h e uniformity value for this system is 9 1 % . S i m i l a r l y after l e v e l i n g o f girdle sprinklers, after looping laterals, operated with low pressure water p u m p and s u b - m a i n l i n e in middle modifications o f 2 0 m m P V C laterals girdle sprinkler
Table 3 . The uniformity values (%) relevant to each modifications system and comparison with drip irrigation system Type of lateral
Before leveling
of girdle sprinkler
After leveling
After looping
With 1" pump
83
86
88
89
91
97
75
91
91
90
94
98
Sub-main in middle
With same girdle
irrigation
Drip irrigation system
,16mm Conduit
87
J20mm JPVC
-
365
SECOND SYMPOSIUM ON PLANTATION CROP RESEARCH
CONCLUSION
Anonymous ( 1 9 9 9 ) . Crop Production
Guide,
Coconut, Directorate o f Agriculture, Chennai. T h e results obtained on P V C laterals and conduit laterals show that P V C laterals, which has 2 0 m m diameter are better than conduit laterals w h i c h has 16 m m diameter for girdle sprinkler irrigation T h e girdle sprinkler s y s t e m , w h i c h c o m p r i s e o n e 2
Dorota,
Z . H. and T h o m a s H. Y. ( 2 0 0 5 ) . F i e l d
evaluation o f c o n t a i n e r nursery
irrigation
s y s t e m s : U n i f o r m i t y o f water application in sprinkler systems. University o f Florida, Gainesville, http://edis.ifas.ufl.edu
kg c n r inlet pressure with s u b - m a i n l i n e in middle
M o h a n d a s , S., Panchanathan, R . M . , Kulandaivelu,
o f the field, having 2 0 m m P V C laterals has 9 4 %
R . and K a n d a s w a m y , P. ( 1 9 8 9 ) . A s s e s s m e n t
o f distribution uniformity. T h e s a m e system- with
o f crop water requirement
16 m m conduit laterals had 9 1 % o f distribution
Indian Coconut Journal Series 2 0 : pp.
uniformity. T h e r e f o r e , this irrigation s y s t e m is a
10-11.
viable method for small s c a l e c o c o n u t cultivation.
for c o c o n u t .
N a m p o o t h i r i , K . U . K . and S i n g h , H . P . ( 2 0 0 0 ) Coconut cultivation technology. Coconut
T h e distribution uniformity o f the girdle sprinkler
D e v e l o p m e n t B o a r d , K o c h i , India.
i r r i g a t i o n s y s t e m c a n b e further i n c r e a s e d b y producing girdle sprinklers with standard levels.
P e a c o c k , B . and Handley, D . ( 1 9 9 8 ) . Drip irrigation must apply water uniformly to b e efficient
T h i s s y s t e m c o n s e r v e s w a t e r as well as labour
http://cetulare.ucdavis.edu/pubgrape/
compared to hose irrigation. It also has less clogging
ig295.htm
i n c i d e n c e c o m p a r e d to drip irrigation so that even
Peiris, T.S.G., Henry Nimal Appuhamy, P.A.,
harvested rain water or water with silt parts can
Nainanayaka, N.P.A.D., Bandaranayake,
be used to irrigate with j u s t a screen filter.
C.K.
and Neil Fernando, M . T . ( 2 0 0 6 ) .
T e c h n o l o g y on A g r o n o m i c Practices ( M u l c h , T h e total cost for one acre girdle sprinkler irrigation
G l i r i c i d i a , Husk pit, I r r i g a t i o n ) . Coconut
s y s t e m w i t h P V C l a t e r a l s is R s : 3 2 , 8 0 0 . 0 0 compaired to R s : 3 1 , 0 0 0 . 0 0 with conduit laterals
Research, Development and Dissemination of Technologies - Growers
( e x c l u d i n g the water p u m p ) .
Perception,
pp. 2 2 - 2 3 . //;: A Diagnostic
Survey Report - 2 0 0 6 . Coconut Research
ACKNOWLEDGEMENTS
Institute, L u n u w i l a 6 1 1 5 0 , Sri Lanka. S o l o m a n , K . H . ( 1 9 9 0 ) . Sprinkler irrigation. Oxford
Authors wish to thank all the s t a f f o f the S o i l s and
& I B H publishing c o m p a n y N e w D e l h i ,
Plan Nutrition D i v i s i o n o f the C o c o n u t R e s e a r c h
Somasiri, L . L . W . , Nadarajah, N., Amarasiri, L . , and
Institute for their invaluable support in conducting
Hammer, R . D . ( 1 9 9 4 ) . Land suitability
this research successfully.
a s s e s s m e n t o f c o c o n u t survey area in the
c o c o n u t triangle. Occasional
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367
