Development of an Automated Irrigation System for Horticultural Nurseries

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Nov 5, 2013 (3 years and 10 months ago)

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1

Development of an Automated Irrigation System for Horticultural
Nurseries



Abdul Aziz Zakaria

Departm
ent of Biological and Agricultural Engineering

Faculty of Engineering

Universiti Putra Malaysia

43400 Serdang,, Selangor DE




Abstract


Horticulture is becoming an important sector in
the agricultural in
dustry. Due to increasing
demand for planting materials, horticultural
nurseries are being established in many parts of
the country. Irrigation is one of the most
important operations for any nursery to produce
salable plants. With increasing cost of labou
r
and less attractive working environment in the
agricultural sector, automation of irrigation and
other agricultural practices, is a necessity in
order for the horticultural industry to survive.

An automated micro
-
irrigation system is being
developed and
evaluated at UPM. An imported
6
-
station controller, solenoid valves, and micro
-
sprayers were installed to irrigate fruit seedlings
grown in ceramic pots. Initial work is on
determining plant water requirements for
scheduling the system operation. For nurse
ries
with enough pressure from the main, use of
battery
-
operated valves are recommended.



1.0

Introduction


Horticulture is widely practiced as an industry
and as a hobby. The horticulture industry is
responsible for the production of fruits,
vegetables, and
ornamentals for local and export
market. Horticulturist in the floral, landscaping
and nursery industries produce ornamental
plants for use in creating attractive surroundings
outside or inside buildings.


The horticulture industry is becoming an
impor
tant sector in the agriculture industry. The
demand for fruits, vegetables, cut flowers and
other ornamentals are increasing every year. The
estimated market value in this sector can be
worth a few billion ringgit. Due to increasing
demand for planting mat
erials, horticultural
nurseries are mushrooming in every part of the
country.





From small roadside nursery to large
-
scale
business by the corporate sector, the
horticultural industry is expanding fast. Starting
with Kuala Lumpur, many other major cities and

local authorities are beginning to beautify their
township with landscaping project. Tree planting
campaigns have been organized by various
government and non
-
government agencies. Our
highways are beautifully landscaped so that it is
really pleasant to dr
ive. If not for the present
economic slow
-
down our horticultural nursery
should have developed much faster. Interest in
agro
-
tourism and agro
-
hobby are steadily
increasing. So, the demand for fruits and other
horticultural plants is expected to increase.



2.0

Automated Irrigation of Nurseries


Nursery plants require water if they are to
develop into healthy salable products. Most
nursery operators irrigate their plants almost

2

daily to replace the moisture lost by
evapotranspiration. For plants that are grown

in
containers like polybags, may require two or
three times more water than plants grown in the
field. A reliable source of water supply is an
important fundamental requirement for
successful operation of any commercial
horticultural nurseries.




Overhe
ad sprinkler and micro
-
irrigation are the
two common methods used in irrigating
horticultural nurseries in Malaysia. For some
smaller nurseries, water hose is still being used
for spraying water to nursery plants. Use of an
automated system is very limited
. With
increasing cost of labour and less attractive
working environment in the agricultural sector,
automation of irrigation and other practices is a
necessity in order for the horticultural industry
to survive.


An automated irrigation system is one whe
re the
amount of water supplied and the time and
duration of irrigation are controlled
automatically by a controller. An automated
irrigation system can be divided into two
categories;


a)

Open Loop System

An open loop control system is defined as a
system i
n which the results of the operation are
independent of the input and an operator is
needed to make decisions, that is when to
irrigate and how much to irrigate, and wrote a
program into the programmable controller.


b)

Closed Loop System

In the closed loop
control system, the input is
directly dependent on the output through a
feedback mechanism from the output to the
input. Closing the loop via the feedback device
allows for comparison of the output with some
reference
-
input signal and precise control syste
m
can be achieved.


2.1
Advantages of Automated System


a)
Reduced Uneven Water Supply

Too much or insufficient water will reduce plant
growth. Where there is insufficient water, the
plants have difficulty absorbing water to replace
water loss through evapotran
spiration. Too
much water will result in water logging on the
soil surface or in the containers where the soil
becomes fully saturated. The plant roots will
have difficulty obtaining oxygen from the soil.
Beside that, too much water will also increase
the
depth percolation losses below the crop root
zone, irrigation runoff from the field and also
surface evaporation. By using automated
irrigation, the controller will control the quantity
of water supplied to plants at the optimum level
required without much

wastage.



b)
Decreased Labour Cost

Using automated irrigation system can minimize
the use of labour. This is because the automated
system can be used to replace some of the work,
which are done manually by human being such
as switch on and off the valve, c
ontrol the
timing, the duration and the quantity of water
needed for irrigation. If the cause of labour is
high, using an automated can save the labour
cost and increase the reward in the future.



c)
Decreased Energy Requirements

Automated irrigation system

can save the water
requirement that is used to irrigate the plants,
especially on the occasion that the quantity of
available water is limited. Normally, the water
used for irrigation purpose is pumped from
pond. When the quantity of water is reduced the
cost of pumping is also reduced. Therefore, by
using automated system, the energy cost of
pumping irrigation can be reduced.


2.2
Disadvantages of Automated System


The cost of an automated system can be high
compared to a manual system. The initial cost of
a

micro
-
irrigation system can be many times

3

higher compared to a sprinkler system irrigating
the same area. Another problem with an
automated system is the tendency of the operator
to ‘set it and forget it.’ This can result in over
irrigation during rainy p
eriod especially for an
open loop system without any rainfall sensors.



3.0

Components of Automated System


a)

Automatic Controllers and Timers




Automatic or programmable controllers and
timers are devices that can be programmed to
operate the solenoid val
ves with any degree of
automation. They range from a simple time
switch, which turns a single solenoid valve on,
and off on a pre
-
set time schedule, to extremely
sophisticated and versatile programs which can
operate a very large and complex area like a 36
-
hole golf course. They send electric signal to
actuate the solenoid valves installed in the
system. Controllers and solenoid valves must be
properly matched for successful operation.


b)

Solenoid Valves




Solenoid valves are water valves that are
actuated
by electric current to raise or lower the
valve disc. Most standard solenoid valves
operate on a 24
-
VAC 50/60 cycle solenoid
power. This is considered safe for ground burial
with underground wire.

c)

Piping System


Whether a sprinkler or micro
-
irrigation
system is
being used, a system of pipes is required to
convey the water to the required areas for
irrigation of nursery plants. PVC, PE, or other
pipe materials can be used for this purpose.


d)

Sprinkler Head/Emitters


Sprinkler irrigation is the most commo
n method
of irrigating nursery. Rotating sprinkler head is
the most common type nozzle. Perforated hose
or pipes are also being used for irrigating plants
grown in closely space polybags. For micro
-
irrigation, micro
-
sprayers, point
-
source emitters,
and per
forated hose are the common methods
used for irrigating plants grown in large
containers.


e)

Pump


For nurseries that depend on surface water for
irrigation, pumping is necessary to develop the
required pressure. Availability of electrical
power source is

essential for automation of
pumping. Electric signal can be sent from the
central controller to the pump to turn on or turn
off the pump.


f)

Soil Moisture Sensor





Soil moisture sensors are devices that monitor
the soil moisture levels and control indivi
dual
solenoid valve to prevent unnecessary irrigation.


g)

Rainfall Sensor


Rainfall sensors are devices that monitor the
rainfall levels and override the controller to
prevent unnecessary irrigation




4







4.0

System Development at UPM


Automated irrigation sys
tem is being developed
at UPM using imported components. A 6
-
station
controller with solenoid valve is being evaluated
for irrigation of fruit seedlings grown in ceramic
pots. Micro
-
sprayers, perforated hose, and mini
sprinklers are being evaluated for the
ir
performances. Battery
-
operated valves are also
being evaluated for application in areas with
sufficient pressure from the main
-
line.



4.1.
Irrigation Water Requirements


Information on irrigation water requirements for
nursery is important in the design an
d selection
of sprinkler or emitter spacing and discharge.
Different size plants will require different
volume of water to meet the evapotranspiration
demand. From past studies on water requirement
for plants grown in containers the water
requirements can
range from 3.0 mm/day in the
shade to 5.0 mm/day for plants grown in the
open. For plants grown in polybags with
drainage holes, the evapotranspiration can be as
high as 12 mm/day.



4.2.
Emitter Selection


For irrigating plants grown in containers, point
sour
ce emitters, micro
-
sprayers, or perforated
hose can be used. Information on discharge
-
pressure relationship for each type need to
known for estimating the duration of irrigation.
For the system set
-
up at UPM, micro
-
sprayers
with discharge
-
pressure relatio
nship of q = 3.62
H
0.56

(q in liters per hour, H in kilopascals) were
used. A 6
-
station controller was installed to
irrigate fruit seedlings grown in ceramic pots.
Battery
-
operated valves were also evaluated at
commercial nursery.


4.3.
System Installation


A 6
-
station controller was set
-
up to irrigate fruit
seedlings grown in ceramic pots. Only three
lateral lines were set
-
up to irrigate pulasan,
water
-
apple, and longan seedlings. Battery
-
operated valves were also used where the
mainline water pressure is h
igh. The schematic
diagram of the installation is shown in the figure
below


4.4.
Evaluation


Results from the water balance study showed
that the average evapotranspiration rate for the
fruit seedlings is about 4.0 mm per day. The
system was operating successf
ully, provided
there is no power failure. The only problem is
that sometimes the solenoid valve did not fully
closed when actuated to do so. This results in
over
-
irrigation for that lateral line. Based on the
moisture characteristic of the soil used, the
s
ystem was program to operate once a day every
day for the peak water demand period of June
through August.


The battery
-
operated valves were installed at a
commercial nursery. The programmable valves
have been working successfully for the past two
years. T
he only precaution that has to taken is to
protect the battery
-
operated valve from rainfall.
The other problem that can happen is clogging
of the valve due to lack of good filtration
system.



5.0

Conclusions


A 6
-
station programmable controller with
solenoi
d valves was set up at Universiti Putra
Malaysia for automated irrigation of fruit
seedlings grown in ceramic pots.


Electricity and water supply (with enough
pressure) are necessary for successful operation.
The system was set up to irrigate only a small
number of plants but can be expanded to operate
more stations (solenoid valves). From initial
water balance study the average
evapotranspiration for the fruit seedlings grown
in large ceramic pots is about 4.0 mm per day.
This system can be used for irriga
tion of larger
nurseries. For smaller nurseries with available

5

water supply from the main, battery
-
operated
programmable valves are recommended.



References


Davidson, H., Mecklenburg, R, and Peterson, C.
1988. Nursery Management


Administration
and Cul
ture. Prentice Hall, Englewood Cliffs,
USA.


Fauzi Abdullah. 1993. Determining Evaporation
and Evaluating Water Requirements Using
Perforated Pipe System of durian Seedlings
Grown in Polybags. M.Sc. Thesis University of
Newcastle
-
Upon Tyne


UPM.


Kooi, S.
L. 1998. Development of an Automated
Micro
-
irrigation System for Commercial
Production of Advanced Planting Materials.
Final Year Project Report. Faculty of
Engineering, UPM, Serdang.


Siti Hawa Perseh. 1997. Water requirements of
Licuala Grandis . Final
Year Project Report.
Faculty of Engineering, UPM, Serdang.


Walter W. Hinz, et al, (Editor: Claude H. Pair).
1975. Sprinkler Irrigation. Sprinkler Irrigation
Association, USA.