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of soil. The exact wetted volume of the soil needs to be determined for providing the
adequate amount of water required by the crop [2, 6].
Therefore, one of the basic needs for an accurate design of drip irrigation system is
precise information about the water movement and distribution patterns in soil. Keep-
ing this in view, the present investigation was carried out to study the movement of
soil moisture under different drip discharges at different system operating pressures.
10.2 MATERIAL AND METHODS
The experiment was conducted at the research farm of Water Technology Centre, In-
dian Agricultural Research Institute (IARI), New Delhi, India (Latitude 28
°
37′30″-
28
30′0″ N, Longitude 77°88′45″-77°81′24″ E and amsl 228.61 m) during 2010-
2011. The soil samples were collected at 0.0-15.0, 15.0-30.0, 30.0-45.0, 45.0-60.0
cm soil depths below the soil surface. The soil at the experimental area was deep loam
soil comprising of 36.9% sand, 41.00% silt and 22.10% clay. The average bulk den-
sity, average field capacity and average saturated hydraulic conductivity of soil were
1.60 g cm
-3
, 0.21 and 1.19 cm h
-1
, respectively. The average bulk density and saturated
hydraulic conductivity were 1.53 g cm
-3
and 1.67 cm h
-1
,
respectively
.
The physical
and chemical properties of the soil samples were also determined and are presented
in Table 1.
°
TABLE 1
Soil characteristics at the experimental site.
Soil depth
Soil comparison
FC,
PWP
BD
Ks
Soil Texture
Sand
Silt
Clay
cm
%
%
%
—
%
%
g cm
-3
cm h
-1
0-15
38.72
40
21.28
Loam
19.8
6.78
1.57
1.65
15-30
36.72
42
21.28
Loam
20.3
7.53
1.65
1.74
30-45
34.72
42
23.28
Loam
22.5
7.60
1.63
1.58
45-60
37.44
40
22.56
Loam
22.8
8.10
1.58
1.74
A fi eld plot of 21 m × 50 m was selected for the experiment. The drip irrigation
system was installed with the main station, which includes one hydro cyclone fi lter
(fl ow rate 27 m
3
.h
-1
, 75 mm size), one sand media fi lter (fl ow rate 25 m
3
.h
-1
, 50 mm
size, silica sand 0.7 mm) with back flush mechanism. Main lines (PVC pipes of 60 mm
diameter) were connected to submains (PVC pipes of 40 mm diameter) for each seven
rows plot through a valve tree, ball valve connector and pressure release valve. Flush
manifolds were connected at the lower end of each block.
Experiment was designed to determine the soil moisture movement with different
dripper discharges under different system operating pressures. The thin-walled drip
line (Azud line, 16 mm diameter with 30 cm dripper spacing and dripper discharge of
1.4 l h
-1
) with 16 mm nominal diameter was used for the experiment. The system was
operated at three operating pressures (0.5 kg cm
-2
, 1.0 kg cm
-2
and 1.5 kg cm
-2
). The
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