Accepted Papers - 3.pdf - UNESCO

March to July, 2004 in the field size of 21 m x 14 m.
The sub main was laid along the width and the
laterals were laid along the length of the
experimental field. Pressure gauge, gate valve and
the filter unit were installed outside the pump house.
Submain of size 63 mm was connected to the filter
outlet with the help of bends, socket, and elbow.
The laterals were laid along the length of the field.
Micro sprinklers and drippers were connected on
laterals at specify spacing.
Monoblock pump (capacity 7.5 hp), pressure
gauge (range 0.0– 6.0 kg/sq cm) and gate valve (65
mm diameter) were used to control water supply
during the experiments. Water from the tube well
was collected in a tank constructed on the ground
surface. The water supply was bifurcated through
two pipes, one to the point source of application
and another was used as an outlet. A pressure
regulator was provided on this pipe to control the
water supply. Experimental details are presented in
the (Table 1).
Measurement of discharge
Micro sprinklers and drip assemblies were
subjected to five different pressures (0.50, 0.75, 1.00,
1.25 and 1.50 kg/cm 2 ) using 16 mm diameter lateral.
The water supplied for the experiment was a closed
loop. A 63 mm diameter PVC pipe was placed over
stake assembly and drippers to confine the discharge
into the plastic container directly. Irrigation water
was supplied from a well, filtered through an inline,
100 mesh screen. Test times varied with pressure,
drippers, micro sprinkler and laterals length used.
The water collected in the containers was measured
with the help of measuring cylinder. The specified
pressure was maintained during the tests within ±
5% of the base value as specified in ASAE standard.
Design parameters
The manifold and its laterals were designed
and operated as double unified system. The micro
sprinkler and drip irrigation system, which were
controlled by a single valve and inline filter. The
details of various design parameters were worked
out as follows:
Area : 12 m x 14 m = 168 m 2 ,
Water source : Tube well fed water tank,
Crop : Bitter Gourd, Climate: Semi-humid,
Wind : 2.5 kmph (acceptable limit),
349
Rainfall : 278.7 mm (during crop growing period),
Soil type : Sandy clay loam,
Infiltration rate : Average 12 mm/hr, ET crop : 10.23
mm, Ground water contribution: Nil
Effective root zoon depth (D): 0.4 m, Field capacity
of soil (FC) : 32 % (by weight)
Permanent wilting point (PWP) : 18% (by weight),
Critical point for system (CP): 0.85 (allowable
moisture depletion 15%), Available moisture
content: 27% (by weight)
Area for micro sprinkler design: 6 m x 14 m = 84
m 2 , Distribution efficiency (ç d ): 50%
Application efficiency ( ç a ): 85%, Lateral
spacing ( S r ): 1.5 m, Emitter spacing (S p ): 0.5 m
Bulk density (W): 1.38 g/cm 3 , Fraction of wetted
area ( W p ) : 0.4
Length of lateral (L 1 ): 14 m, Width of the field (W):
6 m, Spacing between two
laterals (S l ) : 1.5 m, Micro sprinkler spacing (S m ):
2.0 m
Design of drop and Micro Sprinkler
From the above mentioned parameter and field
data, the various parameters of micro sprinkler and
drip irrigation design were worked out separately.
Net depth (d ) of water to be applied in one
net
irrigation
FC − PWP
dnet = × W × ( 1 − CP)
× D × 1000
100
= 11.59 mm
Gross depth (d ) of water to be applied
gross
dnet
d gross = = 13.63 mm
Ea
Irrigation interval
dgross
=
ET
= 1 day
crop
ETcrop crop
= peak ET + losses = 10.2 + 2.2
= 12.4 mm
System capacity
It was assumed that 168 m 2 area will be
irrigated in two hrs in one day and fraction of the
total area wetted = 0.5
The main line was designed using Williams and