Soil moisture distribution pattern under surface subsurface drip irrigation

Soil moisture distribution patterns under
surface and subsurface drip irrigation
Presented by
ARPNA BAJPAI
L-2016-AE-121-D
Course Instructor
Dr. PPS LUBANA
Professor (Soil and Water Engineering)
Course Name : Credit Seminar
Course Code :- SWE -591
Friday, May 4, 2018 1

Micro irrigation system is introduced for increasing the
productivity by economizing the use of water. In this
system, water is applied to plant root zone through
emitters. Water is applied at frequent intervals in
controlled quantities as per the requirements of plant. It
is the most advanced irrigation method with the highest
application efficiency.
Introduction

Moisture distribution pattern is one of the basic
requirements for efficient design and management of an
irrigation system. The knowledge of moisture
distribution pattern helps in the effectiveness of drip
irrigation (Yaragattikar et al., 2003).
This will ensure precise placement of water
and fertilizer in the active root zone.

In the design of the trickle system, the volume of soil
wetted by a single emitter is important. This must be
known in order to determine the total number of
emitters required to wet a large volume of soil to ensure
that the plant’s water requirement would be met.

The volume of soil wetted from a point source is
primarily a function of the soil texture, soil structure,
application rate and the total volume of water applied.
The volume of water applied per irrigation also affects
the width and depth of the wetted soil volume and
therefore influences the optimal emitter spacing

The extent of soil wetted volume in an irrigation system
determines the sufficient amount of water needed to wet
the root zone. In a study by Goya (2014), soil water stored
in the root zone was determined by the volume of wetted
soil.
The water is delivered
continuously in drops at
the crop root zone and
wets the root zone
vertically by gravity
and laterally by
capillary action.

 The soil moisture distribution and its uniformity
within the soil profile under surface drip were
affected by the distance between drippers rather than
distance between laterals. Lesser the dripper spacing,
more will be the moisture distribution.
 Under SDI, the allocation of the irrigation system
plays an important role in soil moisture trend. The
depth of the lateral below soil surface, emitter spacing
and system pressure are important for delivering the
required amount of water to the plant (Badr et al,
2011).

The total volume of the wetted soil and its shape under a
trickle emitter varies widely with
 soil hydraulic characteristics
 number of emitters
 discharge rate
 frequency of water application.

The wetted-soil volume needs to be determined keeping in
view all the factors that affect its shape and volume, and
thus help ensure that the wetted soil volume matches as
closely as possible with crop rooting pattern.
The volume of soil wetted under point source trickle emitter
is primarily a function of the
 soil texture
 soil structure
 Application rate and
 The total volume of water applied
(Lubana et al., 2002; Ekhmaj et al., 2005).

During infiltration, the soil water content changes both
spatially and temporally and redistribution of water in
the soil is strongly dependent on the
 Irrigation method
 Soil type
 vegetation root distribution and
 Rates of water application.
Therefore, for effective design and use of drip systems,
there is a need to predict soil water dynamics taking
into account all these dependencies
(Merill et al., 1978).

Case Studies 1
Monitoring and modeling the three-dimensional
flow of water under drip irrigation
J. Fernandez-Galvez , L.P. Simmonds
Journal Name :- Agricultural water management
Published year :- 2006
Pages :- 197-208
Volume :- 83Friday, May 4, 2018 11

The objectives of the study
(a) To develop and verify a technique for monitoring the
three dimensional spatial and temporal patterns of soil
water content under a drip irrigation system.
b) to produce detailed data-sets of the spatial patterns of
soil moisture immediately before and after a drip
irrigation event, and approximately 24 h after irrigation,
to provide information about the post irrigation
redistribution of water.

Particle size distribution and bulk density at the experimental site
Vertical profiles of bulk density were made by inserting
steel cores of known volume (196 cm3) into the face of
three soil pits
The second horizon shows a remarkable higher bulk density
due to the presence of a ploughed layer developed by intensive
farming. The compact layer just below the depth of cultivation
was also noticed during the installation of the access tubes.

Experimental layout.
Access tubes soil moisture determinations
(56 in 1.56m2)
Batavia lettuces
(row spacing
32.5 cm)
Drip line spacing :
65 cm
Dripper spacing :
40 cm

Capacitance sensors were used for soil water content
determination. The ProfileProbe consists of a sealed composite
rod with six sensors located such that measurements are made at
10, 20, 30, 40, 60 and 100 cm depths in normal operation, with the
probe inserted into the soil via an access tube.
(ProfileProbe from Delta-T
Devices Ltd., Cambridge, UK)
Each sensor generates a 100 MHz
electromagnetic field that
penetrates the soil; the dielectric
properties of the soil are
determined from the standing
wave generated.

Soil hydraulic properties used for model
parameterization

5 cm left 5 cm right
Vertical profiles of volumetric water content (before irrigation,
after irrigation and after redistribution). The four locations
illustrated were all at 5 cm radial distance from dripper 2

5 cm down 5 cm up
Before irrigation profiles of water contents had similar
shapes in the four locations, with two peaks of soil
water content at around 40–50 cm depth and 80–100
cm depth
and a local
minimum
around 60 cm
depth.
There was no evidence in any of these tubes of a large
short-range fluctuation in water content with depth,
which can be characteristic of problems arising from
artefacts of air-gaps between the access tube and the
surrounding soil.

Dripper 2, distance 5 cm Dripper 2, distance 5 cm
After Irrigation After redistribution
Vertical profiles of the changes in water content between before
and after irrigation and the changes in water content between
before irrigation and after 24 h of post-irrigation redistribution
The gain in profile water content around dripper 2,
at 5 cm radial distance from the dripper, was
approximately two times larger in two of the
locations
Spatial variation in soil hydraulic properties resulting in the
radial water flow from the dripper being non-uniform.
The apparent gain in water content in the vicinity of an
access tube being dependent on the principal direction of
view of the sensor.
Differences between the tube locations

Maps of the gain in profile water content (in mm)
measured at each access tube location.
before and after irrigation
before irrigation and 24 h
after irrigation
For all the access tubes that were measured before and
after the irrigation event, the gain in profile water content
in mm equivalent water depth that was generated by
applying the irrigation of 9.7 mm. There is a clear general
pattern of the largest gains in profile water content being
observed in the access tubes closest to the drip source, and
apparently rather little water appearing to penetrate more
than 25 cm radially from the drip sources.Friday, May 4, 2018 20

The effect of distance from the nearest drip source on the measured
gain in profile water content during irrigation. The data points are
from individual access tubes, based on the ‘before’ and ‘after’
irrigation.
Data collected suggest that the radial
penetration of water during the irrigation
was limited to about 20 cm

Area-weighted average gains in profile water content (in
mm) across the ‘unit cells’, for the irrigation event when
9.7mm of water was applied
The standard deviation of the water balance
estimates for the ‘unit cells’ associated with
individual drippers is around 2mm. It is likely
that the greatest contribution to this error is that
the estimation of the area-average water storage
is based on a small number of samples within a
very heterogeneous environment.

After wetting Redistribution
Model prediction after irrigation and 24 h
later
During the redistribution period, 24 h after irrigation, there is a
predominant horizontal distribution of water in the top layer
with very little penetration of water below 25 cm.
The lack of horizontal spatial heterogeneity produces a
symmetrical irrigation bulb that extends radially up to
25 cm distance after irrigation has ceased.
The model captures extremely well the penetration of the
wetting front, showing how the compacted layer at 25 cm depth
impedes the water to flow through it and, as a result of that, the
water is spread out further in the horizontal direction

Dripper 2, After wetting Dripper 2, Redistribution
Contour maps of the three-dimensional distribution of
the gain in volumetric soil moisture content during
irrigation. Contour maps are shown for drippers 2, 3, 6
and 7.

Dripper 3,
After wetting
Dripper 3,
Redistribution

Dripper 6,
After wetting
Dripper 6,
Redistribution

Dripper 7,
After wetting
Dripper 7,
Redistribution
The radial distance of the irrigation bulb after
irrigation is around 10 cm with the wetting reaching 20
cm depth according to the soil moisture measurements.
The spatial pattern in water distribution is quite
different between drippers as would be expected due to
soil heterogeneity, having sites with higher changes in
water content in a smaller volume of soil and sites
where the irrigation bulb is more spread out.
In some cases the irrigation bulb appears off-centre is
due to a displacement of the dripper at the soil surface
with respect to the array.

Conclusions
In each case, there is substantial redistribution of water
during the 24 h after irrigation, such that the gain in
water content of the soil just below the dripper
immediately after irrigation ceased (typically 25–30% by
volume) falls to about 12–15% by volume increase in
water content compared with the water content just prior
to irrigation.

Model predictions capture the impact of the compact
soil layer reducing the penetration of the wetting front
down to 25 cm depth. The simulated irrigation bulb is
symmetric with a homogeneous spread out of the water
supplied showing a larger radial influence extending up
to 25 cm after irrigation and more than 30 cm 24 h
later.

Modeling for predicting soil wetting radius
under point source surface trickle
irrigation
R. Subbaiah*, H.H. Mashru
Agric Eng Int: CIGR Journal
Vol. 15, No.3 Year 2013
Case Studies 2

Objective of the study
To develop a simple heuristic model that
can help to determine the wetting radius
from surface point drip irrigation using
infiltration properties of the soil.

The accuracy of the model is validated by
a) Observing the parameters of the model on
the field and
b) By equating the volume of water supplied
and volume calculated from the geometry of
the bulb defined from above models

Materials and method
Place of the study College of Agricultural
Engineering and Technology
Gujarat, India
Type of soil Clay loam soil
Emitters discharge
rates
0.002, 0.004 and 0.008 m3 h-1.
The experimental site was slip ploughed to 1.5 m to
thoroughly mix the profile and eliminate any
compacted layers, then chiselled to 0.3 m, disked, and
harrowed.Friday, May 4, 2018 33

Radius of wetted bulb (Rw) at depth (d)
The radius of wetted bulb at any depth, d, and time, t,
is expressed heuristically as
where , rw0 is the radius of circular area of entry of water into the
soil (cm) at the surface when time t
The depth of wetting front at any time, ti, is expressed as

Model validation
 Coefficient of determination
 Efficiency coefficient
Nash and Sutcliffe, 1970 Liang et al., 1994Friday, May 4, 2018 35
In order to validate the proposed model, the computed
wetted radius at different depths was compared with
the observed radius of spread from the experimental
set up. The relative agreement of each computed wetted
radius with the experimental data was evaluated using

Result and discussions
Infiltration characteristics of the soil
d = 0.5t0.45
cumulative depth of infiltration The infiltration rate
I = 0.225t-0.55
The depth of infiltration obtained from the double ring
infiltrometer was fitted using Kostiakov equation. The
data obtained were plotted on a double log paper to
obtain the slope and intercept.

Physico chemical characteristics of study soils

for 0.002 m3/hr for 0.004 m3/hr
Observed versus calculated radius of water pool on the
ground surface
Wettedradiusrw/cm
Wettedradiusrw/cm
Wettedradiusrw/cm
The observed rw as a function of time for three emitter flow rates.
It was observed during experiment, that the radial area of ponded
water develops in the vicinity of the drip emitters. The water
infiltrates from this saturated entry area into the soil.
The wetted width was affected by discharge rate of emitter as well
as duration of water application. This may be due to the
increasing discharge rate, which increased the volume of water
supplied in a given duration that created higher volume of wetted
soil zone. Increased duration of application also increased the
wetted volume.
for 0.008 m3/hr
It is observed that the values of saturated entry radius
increase rapidly with time initially but then increase at
a decreasing rate to limit the radius to a constant value,
15.5
cm 21.82
cm
32.5
cm

for 0.002 m3/hr
for 0.008 m3/hr
for 0.004 m3/hr
Observed vs calculated radius of water pool on the ground
surface
The rate of trickle discharge and the hydraulic properties of the
soil had a remarkable effect on the shape of wetted soil zone.
Increasing the rate of discharge and decreasing the saturated
conductivity resulted in an increase in the horizontal component
of wetted area.
Condition when emitter flow rate is less than infiltration capacity
of the soil, the depth attained by the wetting front is mainly
controlled by the irrigation time rather than the application rate.
But when the emitter discharge increases beyond the infiltration
capacity of the soil the horizontal component is increased and a
narrower bulb may be seen.

Volume of water contained in the bulb
The computed cumulative volume with time can also
be approximated well with a polynomial equation of
order four with satisfactory values of goodness of fit
for all emitter discharges
Computed cumulative volume of water stored in the wetted
bulb for different discharges

Conclusion
The depth of wetting front was found to be invariant
with emitter flow rate provided the emitter discharge is
less than the infiltration capacity of the soil bounded
with an impervious layer at the bottom
High value of goodness of fit and efficiency
strengthened the confidence in the validity of the model
proposed to predict geometry of wetted soil zone as a
function of emitter discharge.

The wetted bulb geometry predicted by the equations
above can be considered as satisfactory as the volume of
water contained in the wetted bulb is equal to the volume
of water supplied.
The output of the developed model can be used to
determine the geometry of wetted bulb from surface
point source irrigation for a particular discharge
operating for a specific duration.

Soil Moisture Profile Analysis Using
Tensiometer under Different Discharge Rates of
Drip Emitter
Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 908-917
Shashi Shekhar, Manish Kumar, Anuradha
Kumari and S.K. Jain
https://doi.org/10.20546/ijcmas.2017.611.106
Case Studies 3

To evaluate the effects of discharge
rate on moisture profile in the soil
which is measured by the use of
tensiometer.
Objective

Materials and Methods
Location Experimental farm of Pumps and Wells
laboratory shed of College of
Agricultural Engineering Samastipur
Bihar.
Climate sub- humid- west monsoon
annual rainfall 1270 mm
average minimum and
maximum
temperatures
30– 40˚C and 43 - 44 ˚C
Materials used in the
experiment
Metallic cylindrical tank
Tensiometer

Methodology adopted for the experiment
Determination of soil texture :- Sandy clay loam soil
Determination of bulk density
Installation of tensiometer
Calibration of tensiometer
sand, silt and clay are
52%, 18% and 30 %

Installation of set up for the experiment
Cylinder tank :- soil filled Height (90 cm)
Tensiometer were installed at the radial
distances of 15 cm, 30 cm, 45 cm, 60 cm, and
90 cm.
Discharge rates of 2 lph, 4.4 lph and 6 lph
were used for the experiment. Readings were
noted down at regular interval of 15 min for 6
lph discharge rate and 30 min for 4.4 lph and 2
lph discharge rates.

Plotting of contour maps
Contour maps were plotted from the data
recorded during the experiment for
different discharge rates of 2 lph, 4.4 lph
and 6 lph using the Surfer – 7 software

Results and Discussion
The bulk density of soil sample taken for discharge 2
lph, 4.4 lph, and 6 lph was obtained 1.46, 1.47 and 1.41
g/cm3 respectively.
Bulk density

Soil moisture content corresponding to
soil moisture tension

Calibration of the tensiometer
Soil moisture tension (centibar)
Soilmoisturecontent(%)
27.4%
23.5%

Soil moisture profile at 2 lph emitter discharge
Study of soil moisture profile
Radial distance
Depth
In case of iso-moisture lines (contour lines) having moisture
content 17%, the radial distance is 36.5 cm and for iso-moisture
lines having moisture content 18%, the radial distance is 30 cm.
This clearly shows that as the distance from the centre increases
vertically there is a decrease in moisture content i.e. with increase
in distance from the centre there is a decrease in moisture content.
It can be said that changes in moisture content is steeper radially
than vertically. Thus, it is evident that vertical movement of water is
predominant as compared to lateral movement.

Soil moisture profile for 4.4 lph discharge rate
Radial distance
Depth

Radial distance
Depth
Soil moisture profile for 6 lph discharge rate
It clearly indicates that greater is the distance
from the centre lesser is the moisture content.

Comparison of soil moisture profile at different
discharge rates of emitter
This clearly shows that for the same moisture
content, the radial distance of iso-moisture
lines from the centre is greatest for 6 lph
followed by 4.4 lph and last is 2 lph discharge.
Thus, it can be said that more is the
discharge rate more is the lateral
movement of water.

This clearly shows that for the same moisture
content, the vertical distance of iso-moisture
lines from the centre is greatest for 2 lph
followed by 4.4 lph and last is 6 lph discharge.
Thus, it can be said that lower is the
discharge rate greater is the vertical
movement of water.

The vertical spread of water decreases with increase in
emitter discharge rate. The vertical spread was
observed to be about 18.0% and 32.0% less when
discharge was increased from 2 lph to 4.4 lph and 6.0
lph respectively.
Major Conclusions
Horizontal spread of water increases with increase in
discharge of emitter. The horizontal spread was
observed to be about 25.4% and 47.8% more when the
emitter discharge rate increased from 2 lph to 4.4 lph
and 6.0 lph respectively.

Based on the soil moisture recorded at different
points below the discharging emitter under different
discharge rates it can be concluded that the spread of
water increases in horizontal direction and decreases
in vertical direction when the emitter discharge is
increased.
Hence, the crops which have deeper root
system must be irrigated with smaller
discharge rates compared to crops which have
shallow roots.

ASSESSMENT OF WETTING PATTERN AND
MOISTURE DISTRIBUTION UNDER POINT
SOURCE DRIP IRRIGATION
Binyebebe Maurice, Nsengumuremyi Emile,
and Uwimpuhwe Charlotte
International Journal of Innovation and Scientific Research
ISSN 2351-8014 Vol. 26 No. 2 Sep. 2016, pp. 484-493
Case Studies 4

Objective
Assessment of wetting pattern and
moisture distribution under point
source drip irrigation

Material and methods
STUDY AREA Farm of University
of Rwanda- Nyagatare Campus
Mean annual rainfall 850 mm
Annual mean maximum
and minimum
temperatures
32˚C and 15˚C
Average maximum and
minimum relative
humidity
92 % (8:22 hrs) and 39 % (14:22
hrs)
mean daily
evaporation
3.5 to 7.6 mm

SOIL PROPERTIES OF EXPERIMENTAL
SITE
Texture
Sandy
Loam

T1S1 - Drip lateral at surface with irrigation water at 1.0
IW / CPE ratio
T2S1 - Drip lateral at 10 cm depth from surface with
irrigation water at 1.0 IW / CPE ratio
T3S1 - Drip lateral at 20 cm depth from surface with
irrigation water at 1.0 IW / CPE ratio
EXPERIMENTAL DESIGN

WETTING PATTERN MEASUREMENT
 HORIZONTAL WETTED ZONE
 VERTICAL WETTED DEPTH
The average radius of the
wetted zone was estimated
over time during emission
by measuring the actual
distance in four directions
as the wetting pattern has
almost a circular shape
using the measuring scale.
Immediately after measuring
the horizontal wetting front,
the discharge was stopped.
Then, the soil was cut
vertically along downward to
record the vertical movement
of wetting front after the
specified time

Result
MOISTURE DISTRIBUTION IN SOIL DURING
DIFFERENT PERIOD
Distance from emitters, cm
Depth,cm
30DAS60DAS

Distance from emitters, cm
Depth,cm
90DAS120DAS
Moisture distribution before irrigation at surface, 10
cm and 20 cm depths
While analysing the horizontal behaviour of soil
moisture, the general trend showed that the
moisture decreased with increase in distance
from the emitting point for all the treatments
Philip (1984) and Muthuchamy (1998) that the
moisture content was decreased while the distance
from the emitter point increased.

Moisture content (%) 24 hours after irrigation at 30, 60, 90
and 120 DAS

Horizontal wetting front advancement and
vertical wetted zone depth
the horizontal wetted zone
radius increased linearly
with increase in elapsed
time. It was observed the
faster movement of wetting
front in horizontal
direction for surface drip
treatments than the
treatments of subsurface
lateral installations at 10
cm and 20 cm depth.
Vertical wetting front
advance increased
with increase in
elapsed time. Inversely
to horizontal wetted
zone radius, the
wetting front advance
in vertical direction
was faster in the
subsurface treatments.

Measurement of
wetting pattern at 30
cm depth
Measurement of
wetting pattern at
surface

HORIZONTAL WETTED RADIUS
The following equations representing predicted values
were obtained:
(i) Y (0 cm) = 0.1026X + 10.437 (surface drip)
R2 = 0.8062
(ii) Y (10 cm) = 0.1059X + 6.4858 (sub surface drip, 10 cm depth)
R2 = 0.8621
(iii) Y (20 cm) = 0.1035X + 5.543 (sub surface drip, 20 cm depth)
R2 = 0.891
Where,
Y = horizontal wetted radius, cm
X = elapsed time and
A, C = constants
Horizontalwetted
zoneradius,cm
Time, minFriday, May 4, 2018 70
The range of variation of obtained regression coefficients varied
between 0.8 and 0.9 .This states that the obtained regression line
perfectly fits the data.
indicated that the
variation of
horizontal wetted
radius was highly
correlated to time
increase

VERTICAL WETTED RADIUS
(i) Y (0 cm) = 0.217X + 5.2203 (surface drip)
R2 = 0.9532
(ii) Y (10 cm) = 0.2996X + 5.8946 (subsurface drip, 10 cm depth)
R2 = 0.9647
(iii) Y (20 cm) = 0.2927X + 6.7402 (subsurface drip, 20 cm depth)
R2 = 0.957
Where,
Y = horizontal wetted radius, cm
X = elapsed time and A, C = constants.
Verticalwetted
zoneradius,cm
Time, minFriday, May 4, 2018 71
indicated that the
variation of Vertical
wetted radius was
highly correlated to
time increase

Conclusion
The percentage of moisture was decreasing with increase in
distance from the emitting point in both cases investigated i.e.
before and 24 hours after irrigation.
The surface soil appeared to be almost dry before irrigation in
upper depth of soil say from surface to 15 cm depth. However 24
hours after irrigation is supplied, the moisture content for the
treatments of surface laterals became higher from surface to 15 cm
deep and lesser in the depth of 15 – 30 cm. In case of subsurface
drip treatments, the moisture content observed 24 hours after
irrigation was found to be higher in deeper installation.
Analyzing the contours of 10 cm and 20 cm depths of lateral
placement at different irrigation levels, the moisture content was
evenly distributed 24 hrs after irrigation.Friday, May 4, 2018 72

EFFECT OF SUBSURFACE DRIP IRRIGATION
SYSTEM DEPTH ON SOIL WATER CONTENT
DISTRIBUTION AT DIFFERENT DEPTHS AND
DIFFERENT TIMES AFTER IRRIGATION
DOUH B.*, BOUJELBEN A., KHILA S., BEL HAJ
MGUIDICHE A.
Larhyss Journal
March 2013, pp.7-16
Case Studies 5

Objective
To evaluate soil moisture distribution
before and after irrigation

MATERIALS AND METHODS
Place Higher Institute of Agronomy of
Chott Mariem, Tunisia
Duration May to July 2010
climate Mediterranean
Annual rainfall 230 mm
evaporation 6 mm/day
Avg minimum and maximum
temperature in winter
6 and 18 ℃
Avg minimum and maximum
temperature in summer
23 and 38℃
Soil type sandy loam with average basic
infiltration rate
of 14 mm h-1.
Bulk density 1.40 g cm-3Friday, May 4, 2018 75

Crop Maize
Sowing date 1st May
Crop spacing 80 cm
Irrigation Type Drip irrigation (subsurface)
Emitter depth 5, 20 and 35cm
Location of the dripper respectively at 5, 20 and 35 cm depth

Equipment's used
Soil moisture sensors (Time domain reflectometry tubes)
Emitter discharge :- 4 L.h-1.
Soil moisture was recorded 2 hours before the irrigation, 2, 4,
and 6 h after the irrigation experiment started.
Soil sampling :- 0, 20, and 40 cm away from the emitter and at 10,
20, 30, 40, 50 and 60 cm depths
Trime FM

Moisture distribution patterns
Water distribution in soil profile was presented by
contour maps.
For each treatment, six locations around the drippers
were selected.
The total number of moisture data points was 24
points by depth. These 24 point were arranged in a
matrix of 3 columns and 6 rows and the program
(SURFER 8) was used for developing moisture
content lines.

RESULTS AND DISCUSSION
Soil moisture distribution before and after the irrigation
T1 T2 T3
Before Irrigation
2 h after
Irrigation
4 h after
Irrigation
6 h after
Irrigation
For (T1), and before irrigation,
the water content under the
emitter is at the order of 13%
and then increases from the
emitter to reach high values of
20 to 25%.
2 hours after irrigation, water
content increases to 23% but
remains low at the emitter.
4 hours after irrigation,
moisture increases with
distance from the emitter
After 6 hours of irrigation, the
water content under the
emitter reaches 23% and form
circular curves.
For T2, before irrigation, the
water content varies between 15
and 22%. After irrigation, the
curves of equal water contents of
circular shape around the
dripper have the higher values of
(29%). After four hours of
irrigation, water content
recorded at the emitter is
approximately 24.5% and
decreases away to the sides to
reach values of 18%. After 6
hours and at 30 cm on either side
of the dripper, the water content
is around 13% where it has a
maximum root density.
For T3, before and just after
irrigation, at 20 cm on either
side of the emitter, low water
content of about 17% due to root
uptake has been registered.
After 4 hours of irrigation, there
is a high water content of about
21.5% due to the water source
located at (0,0) and a low water
content at 20 cm on both the
other of the dripper.
After 6 h of irrigation, the water
content is low at the emitter of
about 15% moisture and spreads
to the ends up to 21% at 40 cm
on either side of the dripper.Friday, May 4, 2018 79

Soil moisture distribution in different depths
Vertical Soil moisture distribution respectively under
subsurface drip irrigation (T1), (T2) and (T3) 24 hours
after an irrigation of one hour with 4lh-1 flow
The results show that soil moisture is relatively more
stable for T3 than T1 and T2 with slight difference
except of water’s contributions. The study indicated that
soil moisture content under subsurface drip irrigation at
35 cm depth was more uniform as compared to that at 5
and 20 cm.
The results provide evidence that 35 cm below the soil
surface was so dry as it was hypothesized that SDI
method would improve the water use efficiency of maize
crop by minimizing the evaporative loss and delivering
water directly to the root zone
Soil water content for the depth of 20 to 35 cm was
higher in T3. These results are confirmed by
Bajracharya and Sharma (2005) who put the same
hypothesis to explain the amplification of water use
efficiency of cucumber and tomato crops relatively to
SDI.

Conclusions
This study indicated that soil moisture content
under subsurface drip irrigation at 0.35 m depth was more
uniform in comparison to that at 0.05 m and 0.20 m.
Subsurface drip irrigation allows uniform soil moisture,
minimize the evaporative loss and delivery water directly
to the plant root zone which increases use efficiency and
yield

Hussein Mohammed Al-Ghobari and
Mohamed Said Abdalla El Marazky
Surface and subsurface irrigation systems wetting
patterns as affected by irrigation scheduling
techniques in an arid region
African Journal of Agricultural Research Vol. 7(44), pp. 5962-
5976, 20 November, 2012
DOI: 10.5897/AJAR11.2194
Case Studies 6

MATERIALS AND METHODS
Place Experimental Farm of the College of
Food and Agriculture Sciences of King
Saud University, Riyadh.
Crop Tomato
Irrigation Method Drip Irrigation (Surface and
subsurface)

Layout of experimental field
The study site was divided into two main fields, each
divided into three plots as shown in Figure. One field had a
DI system, while the other had an SI system. The DI and SI
systems consisted of 16 mm inside diameter thin-wall drip
lines with emitter spacing of 50 cm and emitter discharge
of 4 lphFriday, May 4, 2018 84

Physical properties of different soil layers in the
experimental field.

Diagram showing soil sampling locations in lateral
and perpendicular directionsFriday, May 4, 2018 86

Scheduling techniques
 ET-System :- uses weather sensors and automatically
determines the crop ET (ETc).
 automatic (Watermark 200SS-V) sensor
 Control system which was based on automatic
weather station (Davis Cabled – vantage pro2)
Watermark 200SS-V
Davis Cabled –
vantage pro2

Uniformity parameter calculations
where; Cus = Christiansen’s coefficient of uniformity of soil water
content below soil surface,
θi = the measured gravimetric soil water
content at depth i,
θ = the mean gravimetric soil water content, and
N = number of measured points.

Distance from emitter (cm) Distance from emitter (cm)
Soilprofiledepth(cm)
Parallel- 24 h after Parallel- 48 h after
Wetting patterns in lateral and perpendicular directions
in root zone area under drip irrigation system with smart
irrigation scheduling 24 and 48 h after irrigation.

Perpendicular- 24 h after Perpendicular- 48 h after
The distribution of soil moisture with soil
depth was more even with 48 h after
irrigation than 24 h after irrigation in both
lateral and perpendicular directions.The shape and volume of moisture distribution was
homogeneous for 48 hour after irrigation in both parallel
and perpendicular directions, but was non-homogeneous,
with a conical shape with 24 h after irrigation.

Wetting patterns in lateral and perpendicular directions in root
zone area under drip irrigation system with sensor based irrigation
scheduling 24 and 48 h after irrigation.
In the parallel direction, the soil moisture
distribution in the top 20 cm of the soil profile
was better with 48 than 24 h.

The soil moisture distribution throughout the soil
profile was more homogeneous in both parallel and
perpendicular directions with 48 h after irrigation, but
was less homogenous in both parallel and
perpendicular directions for 24 h after irrigation

zone area under drip irrigation system with manually controlled
irrigation 24 and 48 hours after irrigation.
The soil moisture content was higher horizontally
than vertically in both parallel and perpendicular
directions for 48 h after irrigation, but was higher
vertically in both lateral and perpendicular
directions 24 h after irrigation.

It can also be seen that the increase in soil moisture
content from 48 to 24 h after irrigation was higher
parallel to the drip line than perpendicular to the
line.
This trend did not occur for the other treatments.
The best wetting patterns were observed in the
parallel direction, especially under the emitter
compared with the perpendicular direction.

Wetting patterns in lateral and perpendicular directions
in root zone area under sub drip irrigation system with
smart irrigation scheduling 24 and 48 h after irrigation.
Parallel- 24 h after Parallel- 48 h afterFriday, May 4, 2018 95
The distribution of soil moisture with depth was
greater with 48 h after irrigation than 24 h after
irrigation in both lateral and perpendicular
directions.

It was clear that the soil moisture was distributed
deeper for 48 h irrigation. The data show that after
irrigation the soil moisture content increased in
both horizontal and vertical directions to be near
field capacity throughout the soil profile.

zone area under subsurface irrigation system with sensor based
irrigation scheduling 24 and 48 h after irrigation.
The distribution of soil moisture against
soil depth in the parallel direction, both 24
and 48 h after irrigation was greater than
in the perpendicular direction.

The contour lines in the perpendicular direction
were very large under the dripper line compared
with the contour lines in the parallel direction
which were apart from each other

zone area under a subsurface irrigation system with manually
controlled irrigation 24 and 48 h after irrigation.
The increase in the soil moisture content under different
irrigation scheduling techniques was greater vertically
than horizontally, in both lateral and perpendicular
directions 24 h after irrigation

The overall wetted area, delimited by the wetting front was
largest for the manually scheduled DI and SI systems, and
smallest for the smart controller scheduled DI and SI systems,
which was consistent with the results reported by Lubana and
Narda (2001).
Friday, May 4, 2018 100

Coefficients of average uniformity of applied water
(Cus) as a function of soil depth, for drip (DI) and
subsurface (SI) irrigation system using three irrigation
scheduling methods.
The higher value for the SI system can be explained by the
hydraulic gradients existing within the unevenly wetted soil which
cause water movement within the soil profile parallel and
perpendicular to the irrigation lines, resulting in the water
movement within the soil to be more uniformly distributed.
Friday, May 4, 2018 101

Conclusions
1. Using all three irrigation scheduling techniques, smart
controllers; moisture sensors; and manual control; the soil
moisture content under the SI system increased more
vertically than horizontally for 24 h after irrigation in
both parallel and perpendicular directions. The soil
moisture content under SI was also higher horizontally than
vertically for 48 h after irrigation in both parallel and
perpendicular directions.
Friday, May 4, 2018 102

2. The shape of the soil moisture distribution was close
to conical for all the irrigation scheduling techniques
studied. The soil water distribution pattern showed the
highest water content near the drip line under the SI
system for all scheduling techniques, with the water
content increasing with distance and depth in both
lateral and perpendicular directions 24 h after
irrigation.
Friday, May 4, 2018 103

3. The soil moisture contour lines were denser for
the SI system than the DI system with all
irrigation scheduling techniques, for 24 and 48 h
after irrigation in both lateral and perpendicular
directions. This difference may be attributed to the
improved water distribution with SI systems compared with
DI systems.
Friday, May 4, 2018 104

4. The moisture distribution in the soil indicated
the wetting pattern in lateral directions in
both surface and subsurface plots
produced wider soil wetting patterns
especially near the soil surface compared to
the perpendicular direction.
Friday, May 4, 2018 105

Soil moisture distribution under different lateral and
dripper spacing of surface drip irrigation system in
clay loam soil
Sanjay Singh chouhan. K. A asthi, R. K. Nema and L.D.
Koshta
International Journal of Agriculture, Environment and
Biotechnology
DOI Number: 10.5958/2230-732X.2015.00082.0
IJAEB: 8(3): 743-751 September 2015
Case Studies 7
Friday, May 4, 2018 106

Material and Methods
Place Jawaharlal nehru krishi vishwa
vidyalaya Jabalpur Madhya Pradesh
Duration 2012-13 and 2013-14
Climate semi tropical
Annual temperature 25.7°C
average
annual rainfall
1350 mm
Average bulk density 2.65 g/cm3
Field capacity 27%
permanent wilting point 15%.
The soil of the study area was clay loam soil in texture contain clay
28.7%, silt 23.7% and sand 47.6%.Friday, May 4, 2018 107

Experimental Details
Surface drip irrigation system was installed with three
lateral spacing
i.e. T1 – 60 cm,
T2 –80 cm and
T3 – 100 cm
with three dripper spacing S1 – 30 cm, S2 – 40 cm and
S3 – 50 cm in three replication under a split plot design
on the same site.
Friday, May 4, 2018 108

Statistical parameters of soil moisture content
soil moisture distribution pattern varied with the diﬀerent lateral
and dripper spacing, although the same amount of irrigation was
applied in each plot. The mean and median of soil moisture content
in 0-60 cm depth of soil gradually decreases with increase of both
lateral spacing and dripper spacing.
Friday, May 4, 2018 109

Soil moisture contour map for T1S1
treatment
Friday, May 4, 2018 110

treatment
Friday, May 4, 2018 111

treatment
Friday, May 4, 2018 112

treatment
Friday, May 4, 2018 113

treatment
Friday, May 4, 2018 114

treatment
Friday, May 4, 2018 115

treatment
Friday, May 4, 2018 116

treatment
Friday, May 4, 2018 117

treatment
Friday, May 4, 2018 118

Water storage efficiency
Effect of different lateral and dripper spacing on
water storage efficiency
Friday, May 4, 2018 119
This may be due to uniform coverage of
moisture in whole cropped area under
closer lateral spacing as compare to
wider lateral spacing

Conclusion
The soil moisture uniformity under dense dripper
geometry is better rather than wider. Installing the
system at 60 cm lateral with 30 cm dripper spacing
is the one to be recommended as it provide a uniform
moisture distribution with high water storage eﬃciency
of 85.73 % in the active root zone for most vegetable
and cereals crops and leads to better water saving in
clay loam soils.
Friday, May 4, 2018 120

Department Studies
Soil water dynamics model for trickle irrigated tomatoes
Prit Pal Singh Lubana*, N.K. Narda
Agricultural Water Management 37 (1998) 145±161
Results
1) The daily volumetric moisture content in several different soil
layers was monitored for a number of irrigation cycles. The predicted
values are compared with the field observed values in the different
soil layers at the end of each drying cycle. Predicted volumetric
moisture content values are found within 2 to 17% of measured
values.
Friday, May 4, 2018 121

 It is also found that as the evapotranspirational demand
increases, the wetted soil volume decreases.
 Considerable amount of water can be lost due to dispersion
from the root zone into the surrounding soil. It has been noted
that dispersion losses have a profound effect on the soil water
regime and water balance in the root zone.
 To prevent increasing the radius of the wetting front, R(t)
down to the root zone depth, the best time to irrigate is when
water uptake by the roots is at its peak. At this time, the
evapotranspiration rate can best compete with the downward
movement of the wetting front.
Friday, May 4, 2018 122

2 Department study
Simulation of soil moisture profiles for scheduling of irrigations
Anchal K. Jain, V.V.N. Murty
Agricultural Water Management
Volume 10, Issue 2, September 1985, Pages 175-181
A mathematical model for simulating soil water content in the
root zone was developed by taking into consideration soil
physical properties, crop and climatic parameters. The governing
differential equation for unsaturated flow of water in the soil was
solved numerically using the Crank-Nicholson finite difference
technique. The water uptake by plants was simulated by using
two different sink functions. The model predictions were in good
agreement with field data and thus it is possible to schedule
irrigations.
Friday, May 4, 2018 123

Simulation of soil moisture movement under rice field using
Hydrus-2D
MAHESH CHAND SINGH*, ANCHAL KUMAR JAIN AND
SUNIL GARG
Crop Res. 45 (1, 2 & 3) : 45-53 (2013)
Department study 3
Conclusions
 The results from the experiment revealed that the soil
moisture content was more in upper layer of the soil profile as
compared to the lower layers due to effect of puddling.
 The application of Hydrus-2D confirmed that the simulated
depth wise soil moisture content values were in good
agreement with observed data.
Friday, May 4, 2018 124

 The model performance was evaluated by using parameters,
namely, root mean square error, absolute percentage error,
correlation coefficient and model efficiency.
 During validation, the average absolute error varied from 2.19 to
13.21%, root mean square error varied from 0.006 to 0.032 cm,
correlation coefficient varied from 0.773 to 0.996 and the average
model efficiency was 98.6%. The use of Hydrus-2D model can be
successfully adopted for simulating soil moisture profiles under
rice crop.
Friday, May 4, 2018 125

Thank You
Friday, May 4, 2018 126

Soil moisture distribution pattern under surface subsurface drip irrigation

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