chapter 5 micro irrigation system. microirrigation basic concept

CHAPTER 5CHAPTER 5CHAPTER 5CHAPTER 5

MICRO IRRIGATION MICRO IRRIGATION SYSTEMSYSTEM

MICROIRRIGATION BASIC CONCEPT

Main topic to discuss…….

Basic concept of microirrigation Advantages & disadvantages Types of microirrigation Main component Automation of system

MICROIRRIGATION BASIC CONCEPT

Introduction• Micro irrigation includes all methods of frequent water

application, in small flow rates, on or below the soil surface. Ideally, the volume of water is applied directly to the root zone in quantities that approach the consumptive use of the plants.

• Through good management of the micro irrigation systems the root zone moisture content can be maintained near field capacity throughout the season providing a level of water and air balance close to optimum for plant growth.

• In addition, nutrient levels which are applied with water through the system can be controlled precisely.

• During the dry season in humid areas, or in arid climates, micro irrigation can have a significant effect on quality and quantity of yield, pest control and harvest timing.

• This technology was first introduced in Malaysia at the end of the 70s(khusus untuk tapak semaian, ladang bunga dan buah-buahan).

• Then use more widely in vegetables, fruits and ornamental plants farms

• Only suitable for row crops such as fruits and vegetables, and nursery.

• Generally only high value crops are considered because of high capital cost of installing

• Recommended places- where the higher cost for water or supplies are limited.

What is Micro What is Micro Irrigation?Irrigation?

• Micro irrigation refers to systems that apply water at very slow rates to points on the soil surface

• Common English terms for micro irrigation include “trickle irrigation”, “drip irrigation ”, and “sub-irrigation”. Sometimes the system is referenced to the type of emitter, such as “micro-spray irrigation”

• Apply water in precise:– time– location– quantity

General Uses of General Uses of Micro IrrigationMicro Irrigation

• Because micro irrigation usually the most expensive method of applying irrigation water and the system O&M requirements are high, this system of irrigation often used where:

– Crop value is high Crop value is high ==

– Water is expensive and or scarceWater is expensive and or scarce– Slopes are too steep for other Slopes are too steep for other

methodsmethods– Advanced manufacturing Advanced manufacturing

facilities are availablefacilities are available

Simple Micro Simple Micro Irrigation SystemsIrrigation Systems

• Not all systems are complex & expensive• Labor-intensive forms of micro-irrigation

are practiced in many areas

Advantages of Micro Advantages of Micro IrrigationIrrigation

1. Water Savings

Irrigation water requirements can be smaller with micro irrigation when compared with other irrigation methods. This is due to irrigation of a smaller portion of the soil volume, decreased evaporation from the soil surface, and the reduction or elimination of the runoff. The losses due to the evaporation from the soil are significantly reduced compared with other irrigation systems since only a small surface area under the plant is wetted and it is usually well shaded by the foliage. Since the micro irrigation system allows for a high level of water control application, water can be applied only when needed and deep percolation can be minimized or avoided.


2. Smaller Flow Rates

Since the rate of water application in micro irrigation systems is significantly lower than in other systems, smaller sources of water can be used for irrigation of the same acreage. The delivery pipes, the pump, and other components of the system can be smaller and therefore more economical. The systems operate under low pressure (5-30 psi) and require less energy for pumping than high pressure systems. .


3. Application of ChemicalsMicro irrigation systems allow for a high level of control of chemical

applications. The plants can be supplied with the exact amount of fertilizer required at a given time. Since they are applied directly to the root zone a reduction in the total amount of fertilizer used is possible.

There is also an advantage to the frequent application of fertilizers through the system in Florida's humid climate. In case of rain, only a small portion of recently applied fertilizer will be washed out and it can be easily replaced through the irrigation system. This application method is more economical, provides better distribution of nutrients throughout the season, and decreases ground water pollution due to the high concentration of chemicals that could ordinarily move with deep percolated water.

Other chemicals, such as herbicides, insecticides, fungicides, nematicides, growth regulators and carbon dioxide can be efficiently applied through micro irrigation systems to improve crop production.


4. Water Sources with High Salt ContentA significant advantage of micro irrigation is that water with relatively high salt content can be used by the system. For optimum plant growth a certain range of total water potential in the root zone must be maintained. The potential defines how difficult it is for a plant to extract water from the soil. Large negative numbers are characteristic of very dry soils with low total water potentials while potentials near zero reflect soils near saturation. The total water potential in the root zone is a sum of the matric potential and osmotic potential. Since matric potential is close to zero under micro irrigation (high moisture content) the osmotic potential component can be a relatively large negative value, indicating high salt content, without harmful effect on plant growth. This is not true for other irrigation systems.


5. Improved Quality of the Crop• Micro irrigated plants are supplied very frequently with

small amounts of water and the stress due to the moisture fluctuation in the root zone is reduced to the minimum, often resulting in larger and better quality yield. In arid climates, or during dry seasons, the harvest timing can be controlled by proper water management.


6. Adaptation to any Topography

• Micro irrigation systems can operate efficiently on hilly terrain if appropriately designed and managed. Well managed micro irrigation system will not create runoff even on hilly terrain.


7. Additional Advantages of Micro-Irrigation Systems

• During dry seasons or in arid climates disease and insect damage can be reduced under micro irrigation system since the foliage of the plant is not wetted. With a small portion of soil surface being watered, field operations can be continued during irrigation. The water distribution is not affected by the wind for drip irrigation. However, wind can have some effect on jet spray patterns.

• Since only the portion of the soil surface is wetted/water uptake by the weeds between the rows can also be significantly reduced. Micro irrigation systems can also be extensively automated/ decreasing labor and operating costs.

Disadvantages of Disadvantages of Micro Irrigation Micro Irrigation

• To operate satisfactorily, a micro irrigation system have to be correctly designed and managed to account for the physical properties of soil, quality of irrigation water, and water requirement of the grown plants.

• This type of system definitely requires a higher management level than other irrigation systems. With all the advantages listed above, a micro irrigation system is not a system without problems.


1. Clogging• One of the biggest problems encountered

under micro irrigation is clogging of the emitters. The small openings can be easily clogged by soil particles, organic matter, bacterial slime, algae or chemical precipitates. The micro irrigation system requires very good filtration (most often recommended is 200 mesh screen) even with a good quality water supply.


2. Moisture Distribution• Moisture distribution depends largely on the soil type being irrigated by the

micro system. In some soils, for example deep sands, very little lateral water movement (low capillary forces) can create many problems. The wetted volume has a shape approaching a cylinder rather than a hemisphere (Figure 4) since gravity forces dominate. Under these conditions it is difficult to wet a significant portion of the root zone. It is also more difficult to manage the irrigation without deep percolation since only a small amount of water can be stored in the wetted volume desired. Increasing the number of emitters per plant may improve water distribution in the soil. As a result, coarse sands will require much closer spacing of emitters than fine soils. In general, for any soil, the number of emitters and their spacing must be based on the geometry of wetted soil volume.

• It is important to realize that the micro irrigation system wets only a limited portion of the potential soil-root volume. Most of the plants can perform very well under these conditions. However, there is a minimum volume of roots which has to be wetted or a reduction in yield will be observed.


3. Salt Buildup• Micro irrigation systems can use saline water. However, a

problem may occur from salts accumulating at the edges of the wetted zone during prolonged dry periods. Light rain can wash these salts into the root zone and cause injury to the plants. In arid climates, where the rainfall is less than 10 inches per year, an additional irrigation system (sprinkler or surface) may be necessary to leach accumulated salts from the soil between growing seasons. In areas with heavy rainfall the salts will be washed out of the root zone before significant accumulation occurs.


4. Initial Cost• The initial investment and maintenance cost for a

micro-irrigation system may be higher than for some other irrigation methods. Filters, chemical injectors and possible automation components add to the cost of a micro irrigation system. Actual costs will vary considerably depending on the selection of a particular micro system, required filtration equipment, water quality, water treatment and selection of automation equipment.


5. Additional Drawbacks• Rodents and insects can create additional

maintenance problems by chewing holes in the plastic. In addition, some components of the system can be easily damaged by persons unaware of their locations.

• A micro irrigation system does not provide significant frost protection; therefore it is not suitable for that purpose.

Types of micro-irrigation

• Drip.• Sprayer • And micro sprinkler

System ComponentsSystem Components• Pumping and motor unit• Delivery system

• Main• Sub Main• Manifold• Lateral (sisi)• Riser (Paip Tegak)

• Water applicators – Emitters– Bubblers– Sprayers– Spitters– Misters– Others

System Components

• Control head– Valves– Filters & screens– Chemical storage– Chemical injection

equipment– Flow rate or volume

meter

System Components

• Other Equipment– Valves– Air vents– Vacuum relief valves– Pressure relief valves– Various pipe fittings

& appurtenances

Pressure Variations Pressure Variations over the Fieldover the Field

System ComponentsSystem Components

Komponen dan bentangan (layout) bagi pengairan Mikro.

Pump and Engine• Pam size selection – suitable discharge –refer

to table

• Penentuan keperluan kuasa engin dan pam dipengaruhi oleh kadaralir yang diperlukan, saiz paip, jenis penyebar dan perbezaan ketinggian antara pam dan kawasan tanaman.

• Pada asasnya, kuasa pam dikira terlebih dahulu kemudian barulah kuasa engin/motor dikira setelah mengambilkira faktor kecekapan

Paip Utama (main)• Paip main boleh diperbuat dari paip PVC kelas

C atau D, besi G.I atau abestos simen.

• Tempoh hayat setiap bahan ini masing-masing 20 – 40, 20 – 40, dan 10 – 20 tahun.

• Paip main sebaiknya dipasang merentasi tengah ladang dan ditanam bawah tanah sebagaimana paip submain.

Paip Sub-utama (submain)

• Paip submain berfungsi sebagai pembekal kepada beberapa manifold.

• Ia biasanya menggunakan paip PVC 50 – 155 mm garispusat kelas C atau D.

• Panjang paip bergantung kepada bilangan manifold dan jaraknya.

• Penentuan saiz paip adalah seperti paip sisi dan manifold.

• Paip submain perlu ditanam antara 0.6 – 0.9 m dalam.

• Ia biasanya dipasang selari dengan manifold

• Di kawasan tanah rata, submain boleh menerima manifold di kiri dan kanan, dan cara ini lebih ekonomik

Paip Pengepala (manifold)• Manifold merupakan sub-unit yang mengandungi

beberapa paip sisi.

• Ia bertujuan untuk mengawal tekanan supaya perbezaan tekanan tidak melebihi 20 %.

• Setiap manifold perlu disediakan injap pintu.• Biasanya diperbuat daripada paip PVC kelas D dan di

tanam 15 – 30 cm.

• Saiz bergantung kepada kadaralir, biasanya antara 25 – 100mm garispusat

• Ukuran panjang bergantung kepada bilangan paip sisi serta jaraknya dan rupabumi.

Paip Sisi (Lateral)• Paip sisi ‘low density polyethylene ‘ (PE) yang sering digunakan

terdiri dari paip yang bergarispusat 13, 16, 18 dam 25 mm.

• Kebanyakkan menggunakan paip berukuran 12 – 16 mm sahaja kerana kos yang lebih rendah.

• Panjang paip perlu sependek mungkin bagi mengurangkan perbezaan tekanan antara salur masuk dan hujung.

• Faktor utama menentukan had panjang paip ialah kadaralir per unit panjang, saiz paip, kecerunan dan bentuk blok tanaman.

• Sebaiknya satu paip bagi satu baris tanaman

• Ia boleh diletakkan di atas permukaan tanah atau di tanam 10 – 15 cm dalam berhampiran batang pokok

• Paip dipasang kendur atau zigzag bagi menyerap pengembangan paip kerana kepanasan dan untuk memudahalihkan paip semasa kerja pembersihan ladang

Jenis Penyebar (emitter)Penyebar yang biasa digunakana. Penitis

- satu @ > titik penyebaran- kadar alir 2,4,8,lsj setiap titik penyebar- tekanan operasi 7 – 14 m (10 – 20 psi)

b. Penyembur (sprayer)- penyebar semburan jet (spray-jet) @ penyebar semburan pusing (spinner)- kadaralir 30 – 60 lsj- tekanan operasi 7 – 14 m- garispusat basah , 2 m

c. Pemercik Mikro- kadaralir 150 lsj- tekanan operasi 7 – 21 m (10 – 30 psi)- garis pusat basahan 2 – 6 m

Water applicator (emitter) selection

• Depends on – Soil characteristic– topografi– Crop water needs– Water source

Drip

Water applicators (emitter)

A dripper in action

Penyebar (emitter) bagi pengairan mikro

Sprayer

Micro-sprinkler

Thin-wall drip line

Tape or Continuous Line Micro Tape or Continuous Line Micro SystemsSystems

Atur Letak Penyebar

• Penyebar boleh di letak dalam pelbagai cara sebagaimana di tunjukkan dalam rajah di bawah

Emitter LayoutsEmitter Layouts• Many

configurations are designed to increase percent wetted area, yet be economical

• Tradeoffs between flow per lateral & total pipe length

Kaedah pemasangan emitter pada paip lateral

Emitter dipasang mengelilingi pokok

Pemasangan Paip Sisi Pada Paip Utama

Sistem Penapis Air• Sistem pengairan mikro memerlukan penapis air yang

berkesan bagi mengelak penyebar dari tersumbat.

• Jenis penapis yang biasa digunakan;– Jejaring (screen)- (3 – 1000 meter padu/jam)– Cakera beralur/lurah (grooved disc)– Pasir (sand)- (45 – 450 meter padu/jam)

• Saiz penapis bergantung kepada kadaralir dan saiz jejaring penapisan (mesh)

• Kapasiti penapis hendaklah 20% lebih tinggi daripada kadaralir sistem

• Pemilihan jenis penapis bergantung kepada mutu air dan kos penapis.

• Air jernih boleh menggunakan penapis jejaring dan cakera beralur. Ia murah dan mudah diguna.

• Air berkelodak dan berlumut memerlukan penggunaan penapis pasir dengan mesh 155 – 200. Harga penapis pasir agak mahal.

• Penapis disambung terus kepada paip utama dan biasanya terletak dekat rumah pam. Ia dipsang antara pam dan injap sehala.

Peralatan Kawalan, Pengawasan dan

Keselamatan• Water meter- to measure volume of water supplied.• Pressure relief valve- to relise water automatically when the

over pressure in system Injap Pelega Tekanan berfungsi untuk mengelakkan sistem daripada rosak dengan membenarkan air dilepaskan secara automatik bila tekanan di dalam sistem berlebihan.

• Check valve – prevent back flow when pump not functionInjap Sehala adalah alat yang berfungsi untuk mengelakkan pengaliran balik air bila pam tidak berfungsi.

• Flow control valve – control the flow direction in the systemInjap Kawalan Aliran berfungsi untuk mengawal arah aliran air di dalam sistem.

• Pressure gauge- to measure water pressure in any point of the systemTolok Tekanan untuk mengukur tekanan air di sebarang titik di dalam sistem.

Pemasangan• Pemasangan sebaiknya dimulakan dengan

pemasangan pamset dan alat kawalan berkaitan dengannya, penapis, injap dan lain-lain.

• Ia diikuti dengan pemasangan paip utama.

• Jentera ‘backhoe’ digunakan untuk menggali parit-parit kecil bagi menanam paip utama, subutama dan pengepala

• Paip PVC disambung dengan menggunakan ‘solvent weld’ dan hujung paip perlu bersih.

• Peralatan kawalan seperti injap pelega udara, injap pintu dan meter tekanan boleh dipasang serentak.

• Paip manifold boleh dipasang sel;ari serta diatas paip submain di dalam satu parit. Ia boleh menjimatkan masa dan kos.

JENIS-JENIS TANAMAN • Tanaman Jangka Pendek- Jagung, Sayur

dan Kacang Tanah• Tanaman Dusun atau Komersial- Durian,

Belimbing, dokong atau mempelam• Tanaman Hiasan - pokok memanjat,

pokok malar hijau, kaktus dan lendair, palma.

• Tanaman di Tapak Semaian - Semua jenis tanaman yang dibiakkan sebelum ditanam diladang atau dijual.

Automation systemA controller

• A controller is an integral part of an irrigation system.

• It is an essential tool to apply water in the necessary quantity and at the right time to sustain agricultural production and to achieve high levels of efficiency in water, energy and chemical uses.

• Irrigation controllers have been available for many years in the form of mechanical and electromechanical irrigation timers.

• These devices have evolved into complex computer-based systems that allow accurate control of water, energy and chemicals while responding to environmental changes and development stages of the crop.

Basic control strategies

• Two general types of controllers are used to control irrigation systems: – Open control loop systems, and – closed control loop systems. The difference between these is that

closed control loops have feedback from sensors, make decisions and apply decisions to the irrigation system.

On the other hand, open control loop systems apply a preset action, as is done with irrigation timers.

Open Control Loop Systems

• When using an open control loop system, a decision is made by the operator or the amount of water and the time at which this water should be applied.

• The operator then goes on to set an irrigation controller according the desired schedule. These devices require external intervention they are referred to in control terms as open loop systems.

• Open loop control systems use irrigation duration or applied volume for control purposes.

• Figure 1 shows the basic components of an open loop time- based irrigation controller. Notice that in this type of controller the basic control parameters are how often and how long is irrigation water is to be applied.

• Open loop controllers are also constructed in such a way that a clock is used to start irrigation and the application of a given volume to stop irrigation.

• In this type of controller the parameters set by the system operator are how often and the volume of water to be applied.

http://edis.ifas.ufl.edu/LyraEDISServlet?command=getScreenImage&oid=16726739

• Open loop control systems have the advantages that they are low cost, readily available, and many variations of the devices are manufactured with different degrees of flexibility related to the number of stations and schedule specification.

• However, they do not respond automatically to changing conditions in the environment and require frequent resetting to achieve high levels of irrigation efficiency.

Closed Control Loop Systems

• In a closed control loop the operator sets up a general strategy for control.

• Once the general strategy is defined, the control system takes over and makes detailed decisions of when to apply water and how much water to apply.

• This type of system requires that feedback be given back to the controller by one or more sensors.

• Depending on the feedback of the sensors, the irrigation decisions are made and actions are carried out if necessary. It is important to note that in this type of systems the feedback and control of the system is done continuously.

• Figure 2 shows the elementary components of this type of system.


• Closed loop controllers require data acquisition of environmental parameters, such as, soil-moisture, temperature, radiation, wind-speed and relative humidity.

• The state of the system (for example measured soil-moisture using a sensor as illustrated in Figure 2) is compared against a desired state and a decision based on this comparison is made whether irrigation should be applied or not.

• Closed loop controllers for irrigation systems base their irrigation decisions on: – 1) direct measurement of soil-moisture using sensors, – 2) calculations of water used by the plants based on

climatic parameters, or – 3) both soil moisture sensors and climatic parameter

measurements.


• When using a computer-based controller, a very important component of a closed loop control system is the logic that is used to make decisions about operation of the irrigation system.

• Some of these systems may be very elaborate and use complicated simulation models that are verified with soil moisture measurements to arrive at an irrigation decision and implement the action at the appropriate time.

• Systems of this type (with different levels of complexity), are quickly being developed, and some have become commercially available in the past few years.

• The simplest form of a closed loop control system is that of a high frequency irrigation controller that is interrupted by a moisture sensor.

• Figure 3 shows this system. The sensor in Figure 3 is wired into the line that supplies power from the controller to the electric solenoid valve.

• The sensor operates as a switch that responds to soil moisture. When sufficient soil-moisture is available in the soil, the sensor maintains the circuit open.

• When soil-moisture drops below a certain threshold, the sensing device closes the circuit, allowing the controller to power the electrical valve.



• Using their arrangement in Figure 3, the controller can be set to irrigate at a very high frequency (4 or 5 times more often than required).

• When the controller attempts to irrigate, irrigation will occur only if the soil-moisture sensor allows it, which in turn occurs only when soil-moisture has dropped below acceptable levels.

• The system has been used successfully in controlling small sprinkler irrigated turf and microirrigated citrus at a research site using switching tensiometers.

• For turf, the tensiometers were installed at the center of the bottom third of the root system (10 inches deep) and the threshold was set to the point at which water stress symptoms were visible.

• In citrus a bank of sensors was used under the emitter connected in parallel, in such a way that any of the sensors would allow irrigation to occur.

• The feedback system in Figure 3 is very low cost and is easy to install and maintain.

• However, the system has limitations: – 1) Determining the best location of the

sensor is not a straight forward task and requires some knowledge of soil-water and root dynamics,

– 2) spatial variability of soil properties may result in readings that are not representative of the system.


Irrigation timers

• Irrigation timers are simple controllers consisting of clock units capable of activating one or more subunits of the irrigation system at specified times.

• Several designs are commercially available with many different features and over a wide range of costs.

• The two most common types of controller designs are electromechanical and electronic. – Electromechanical Controllers

• Electromechanical controllers use an electrically driven clock and mechanical switching (gear arrays) to activate the irrigation stations. These types of controllers are generally very reliable and not too sensitive to the quality of the power available

– Electronic Controllers• Electronic controllers rely on solid state and Integrated

circuits to provide the clock/timer, memory and control functions. These type of systems are more sensitive to powerline quality than electromechanical controllers

Computer-based irrigation control systems

• A computer-based control system consists of a combination of hardware and software that acts as a supervisor with the purpose of managing irrigation and other related practices such as fertigation and maintenance.

• This is done by the use of a closed control loop.

• A closed control loop consists of: – 1) Monitoring the state variables, – 2) comparing the state variables with their desired

or target state, – 3) deciding what actions are necessary to change

the state of the system, and – 4) carrying out the necessary actions. Performing

these functions requires a combination of hardware and software that must be implemented for each specific application.

Hardware Components– Sensors– A/D (analog to digital) interface– Computer system

Software Components

actuators (automatic valves)

• Valves specifically designed for remote control are an important component of the irrigation control system.

• These type of valves are constructed using different materials. Typically brass, stainless steel and a wide array of plastics.

• Different valve actuation designs are used to operate the valves: – 1) diaphragm type, – 2) piston type, – 3) and electric thermal motor type.

MICRO IRRIGATION MICRO IRRIGATION DESIGNDESIGN

Topic to discuss…………….

Determining factors Relationship between discharge and

emitter operating pressure Comparision of Emitter wet diameter

in sandy, loamy and silty soil Micro irrigation design parameters

factors to determine selection of..........

• Type of emitter• Main and lateral pipeline size• Emitter spacing and number

Type of emitter selection

• Based on • soil type, • topographi, • crop water reqirement and • water source.

Bil Faktor Jenis Penyebar Disyorkan

1. Ciri Tanah;a.Tekstur Tanah Kasar-SederhanaSederhana-Halusa.Permukaan Tanah Liat Retak

Penyembur & Pemercik MikroPenyembur & PenitisPenyembur & Pemercik Mikro

2 Rupa bumi/kecerunanRata (<3%)Beralun (3-10%)Curam (>10%)

Semua sesuaiPenyembur & PenitisPenitis

3 Keperluan Air Tanaman<150lph150-200lph>200lph

Semua sesuaiPenyembur & PenitisPenyembur

4 Kuantiti AirTidak TerhadTerhad

Semua sesuaiPenitis

5 Kualiti AirJernihBerkelodak atau mengandungi zat besi

Semua sesuaiPenyembur & Pemercik Mikro

6 Penyakit PokokKurang sensitifSensitif

Semua sesuaiPenitis

Jadual 14.1 : Ringkasan Jenis Penyebar dan Faktor Pemilihan

Selection of main and lateral pipe size

• Recommended lateral – LDPE material (sunprove, longlife-up to 20 yrs).

• Size recommended- 13 mm, 16 mm, 19 mm dan 25 mm.

• Main factors determining the length limit– Discharge per length unit– Pipesize– Slope– Shape of crop block

• Main and submain recommended - PVC and HDPE.

• Main pipe buried - 60 cm depth• Sub-main pipe buried - 30 cm depth.

Diameter nominal paip sisi

(mm)

Had kadaralir

yang dibenarkan

(gpm)

Had panjang

yang disyorkan

(m)

Kehilangan geseran

dalam paip (m/100m)

13 1.0 100 5.0

10 2.5 100 5.0

25 8.0 100 7.0

Jadual 14.2 : Had kadaralir dan had panjang paip sisi untuk kawasan tanah rata.

Diameter Paip (mm)

Had Kadaralir Yang Disyorkan(m3/jam)

Had Panjang Yang Disyorkan

(m)

12/13 0.10.25

Sehingga 300Sehingga 100

16 0.250.5


19/20 0.51.0


25 1.02.0


Jadual 14.3 : Saiz paip sisi dan had kadar alir yang disyorkan untuk tanah rata

Diameter nominal

paip (mm)

Had kadaralir

dalam paip (gpm)

Kehilangan geseran dalam paip

(ka/100ka @ m/100m)

25 14 9.00

32 22 6.20

40 30 5.20

50 50 4.00

80 100 2.40

100 180 2.00

150 360 1.20

Jadual 14.4 : Had Kadaralir yang disyorkan untuk paip utama dan sub-utama.

Selection of emitter spacing and number

• Emitter spacing and no.for each crop depend on;– Wet pattern– Crop spacing

• Soil water movement in horizontal and vertical shoul be known to achive an accurate design.

• No.of emitter for each crop depend on;– % of shaded area– Wetting area of each emitter .

• No.of emitter required for each crop determine by using the formula

Kedalaman akar @ tanah serta tekstur tanah

Tanah sejenis (m)

Tanah berlapis

Ketumpatan rendah

(m)

Ketumpatan

sederhana (m)

0.75 m dalamkasar

sederhanahalus

0.450.901.05

0.751.21.5

1.051.51.8

1.5 m dalamkasar

sederhanahalus

0.751.201.50

1.42.12.0

1.82.72.4

Jadual 14.5 : Diameter basah maksima untuk satu penyebar

4

).(

)(%

2wD

apn

penyebarsatuolehdibasahiluas

pokokperluasxnaungann

Formula Emitter no./crop

dimana,• n – no.of emitter per crop• p – % shaded area• a – crop area (luas tanaman per pokok)• Dw – wetting diameter for each emitter

Jenis tanah Dw (m)

Pasir 0.6-1.5

Kelodak 1.5-2.7

Liat 2.7-4.3

Jadual 14.6 : Jenis tanah dan diameter basah

Relation between discharge and emitter operating

pressure• Consist of fixed type and variable size types. The fixed size emitters

do not have a mechanism to compensate for the friction induced pressure drop along the lateral while the variable size types have it.

• Emitter discharge may be described by:

xKhq • Where:

– q is the emitter discharge L/s; – K is constant for each emitter ; – h is pressure head at which the emitter operates and – x is the exponent characterized by the flow regime.

Jenis Penyebar K x

Aliran jauh (saiz besar)

0.00018 0.63

Aliran jauh (saiz sederhana)

0.000073 0.63

Aliran jauh (saiz kecil)

0.000042 0.63

Orifis 0.00038 0.46

Tiub dua dinding(double wall tube)

0.00046 0.50

Jadual 14.7 : Contoh nilai K dan x

Perbandingan diameter basah penyebar pada tanah pasir, lom

dan liat

Parameter rekabentuk pengairan mikro

• Kadar Penyejatpeluhan Rekabentuk• Pekali Perubahan Luahan Penyebar (CV)• Keseragaman Penyebaran• Kehilangan Turus Dalam Paip

Penghantaran• Perubahan Turus Pengendalian Yang

Dibenarkan• Kapasiti Sistem

Design of ET Rate

• Where: – ETt is average evapotranspiration rate for crops under

trickle irrigation; (kadar penyejatpeluhan rekabentuk (mm/hari))

– P is the percentage of the total area shaded by crops; (peratus kawasan yang dinaungi tanaman (%))

– ET is the conventional evapotranspiration rate for the crop (kadar penyejatpeluhan lazim, mm/hari)

– Sekiranya P85, maka ETt = ET

85.P

ETETt

Karmeli and Keller (1975) suggested the following water use rate for trickle irrigation design

Keadaan iklim Kadar ET (in/hari)

1 Sejuk lembab 0.10-0.15

2 Sejuk kering 0.15-0.20

3 Hangat lembab 0.15-0.20

4 Hangat kering 0.20-0.25

5 Panas lembab 0.20-0.30

6 Panas kering 0.30-0.45

Jadual 14.8 : Pengaruh iklim terhadap kadar penyejatpeluhan air

E.g. :If a mature orchard shades 70% of the area and the conventional ET is 7 mm/day, the trickle irrigation design rate is ?:

Solution :

So, 7/1 x 70/85 = 5.8 mm/day

85.P

ETETt

Emitter Discharge manufacturer's coefficient of variation (Pekali

Perubahan Luahan Penyebar (CV))

• Water application efficiency in irrigation depend on;

• Variation of emitter discharge• Pressure difference along lateral• Water loss through evaporation• percolation

• Pekali perubahan luahan penyebar, Cv adalah antara 0.02 – 0.4.

Emitter Uniformity• Coefficient variation (Cv) yang boleh diterima adalah <0.15 bagi

penyebar jenis punca titik dan <0.20 bagi penyebar punca talian. • Keseragaman penyebaran bagi sistem mikro boleh ditentukan

dengan dua persamaan berikut;

5.0

8.01

n

CEU V

avgv q

qC

nEU min

5.0

27.10.1100

dimana• EU - Keseragaman

penyebaran• Cv - Pekali perubahan

penyebaran• n - Bilangan penyebar

setiap pokok (n=1 untuk penyebar punca talian)

• qmin - Kadar luahan penyebar minimum

• qavg - Kadar luahan penyebar purata

Friction head loss in delivery pipe

Kehilangan Turus Dalam Paip Penghantaran

dimana• Hf - Jumlah kehilangan turus geseran dalam

paip,m• K - Pemalar, 7.89 x 105• L - Panjang paip,m• Q - Kadar luahan,l/s• D - Diamater dalam paip,mm

75.4

75.1

D

KLQH f

Perubahan Turus Pengendalian Yang Dibenarkan

• havg - Turus atau tekanan rekabentuk

• hmin - Turus atau tekanan minimum dalam sesuatu bahagian

)(5.2 minhhh avg

System Capacity

• Pemilihan saiz pam yang sesuai untuk kadaralir yang diperlukan dapat dibuat berpandukan jadul di bawah;

Saiz Pam (mm) Kadaralir (m3/jam)

50 30-60

75 60-100

100 100-140

125 140-180

150 180-220

adual 14.11 : Jadual Pemilihan Saiz Pam

Procedure to calculate Q

1. System efficiency (T)

T = Eu x a

2. Water quantity

v = ETt x a x Cf

ηtWhere;

V = water volume (L/day) ETt = Design ET rate (mm/day)a. = crop area (m2) or root zone area Cf = crop factor (kematangan

Cont…….3. Discharge rate for each crop

4. Discharge rate for each emittert

Vq p

n

qq ps

5. Water in root zone Kehadiran Air Dalam Zon Akar

(water Amount = MHC x Rz volume)

6. Max. Total amout of water required for each crop Jumlah Air Maksimum Yang Diperlukan Oleh Setiap Pokok.

(Jum air akarx 0.5 x susutan LembapanTerizin)

Kecekapan Pengairan

Cont……..

TD

AkarZonIsipadu43

1 2

7. Irrigation interval Selang Masa Maksimum Antara Pengairan

sela = Jumlah air perlu diberi v

8. Operation time Jangkamasa Operasi Pada Setiap Penggunaan

9. System capacityQ=qn

Cont…….

PenitisperKadaralirXPokokperPenitisBilangan

PokokSetiapDiperlukanYangAirMaksimaJumlahmasaj /

EXAMPLE : NO.1

Calculate the daily water needs of each plant based on the information below:

Given; Evapotranspiration, 7.5 mm/dayCrop spacing , 6 x 6 m2Crop factor, 0.5% of crop shaded area 80%System efficiency 85%

SOLUTION :

Given; Evapotranspiration, 7.5 mm/dayCrop spacing , 6 x 6 m2Crop factor, 0.5% of crop shaded area 80%System efficiency 85%

• = 7.5mm/day x 80/85• = 7.06 mm/day

v = ETt x a x Cf

ηt

= 7.06 x 6x6x0.5/0.85

= 149.5 L/day

85.P

ETETt

EXAMPLE :NO.2

i. Calculate the water discharge rate (L/s) if the total head of pipe friction loss is3m for each 100m of pipe and the diameter pipe are 12 mm.

ii. If the 16mm diameter pipe are used for supply the same water discharge rate, calculate the total friction loss head for each 100m of pipe.(assume values of K is 7.89 x 105)

SOLUTION :

• 3 = 7.89 x 10exp5 x 100x Qexp1.75

12 exp4.75Q = 0.05 L/s

75.4

75.1

D

KLQH f

EXAMPLE : NO.3

Given Data:• Farm size: 150 m x 150 m• Crop Spacing: 6 m x 6m• Wet Diameter: 2.5 m• Evapotranspiration:8 mm/day• % of crop shaded: 80 %• Crop Factor :1.0• Variable coefficient:0.12

calculate• Design evapotranspiration rate

(ETt)• Number of emitter for each plant

(n)• System efficiency by assuming

that the irrigation efficiency is 90 % (ηT)

• Number of plant on the field• Total number of emitter• The daily volume of water for

every plants (v)• The emitter discharge if the

system operation is 5 h/day (qe)• The system capacity (Q)

SOLUTION :

i. iii.

ii.

daymmET

daymmET

PETxET

T

T

T

/53.7

)85

80)(8(

85

687.590.4

33.2

4/)(

)66)(80.0(

2

2

2

nm

mn

D

xn

A

Pan

w

w

96.0

96.040.01499.2

096.01

6

)12.0(8.01

)(8.01

5.0

5.0

EU

EU

EU

EU

n

CEU v

%4.86

864.0

)96.0)(90.0(

))((

T

T

T

aT Eu

iv. v.

vi.

62536

22500

)6)(6(

)150)(150(

p

p

p

p

fp

n

n

n

a

an

3750

)6)(625(

.

et

et

pet

n

n

nnn

dayliterV

V

CaETV

T

fT

/75.313

)864.0

1)(.36)(53.7(

..

vii.

viii.

hq

q

n

qq

e

e

pe

/45.106

.75.62

.

hq

dayh

dayq

t

Vq

p

p

p

/75.62

/5

/75.313

hQ

Q

nqQ pp

/75.39218

)625)(75.62(

.

EXAMPLE : NO.4

Calculate the total friction head of PE pipeline in to micro-irrigation system as layout in Figure S5, Friction Loss Characteristic-P.E pipes table and appendix 1.

DATA• Emitter discharge : 0.15 gpm• No. of emitter recommended for

each crop : 2 • Total crop : 100• Hf in fitting and filter : 20% of Hf

in pipe line• Safety factor added : 12%.• Type of pipe used in main and

lateral pipeline : P.E pipe

8pkk

8pkk

8pkk

8pkk

8pkk

8pkk

8pkk

8pkk

12pk

k

12pk

k

12pk

k

A B C D E F G H

I

CONT……..

bahagian

Saiz paip (in)

Jarak paip (ka)

Kadaralir (gpm)

PSI/100’ panjang

Jumlah PSI

A – B 1.25” 40

B – C 1.25” 30

C – D 1.25” 30

D – E 1.25” 30

E – F 1.25” 30

F – G 1.25” 30

G – H 1.25” 30

Lateral

0.5” 1008p

kk

8pkk

8pkk

8pkk

8pkk

8pkk

8pkk

8pkk

12pk

k 12pk

k 12pk

k

A B C D E F G H

I

SOLUTION :

SEKIAN TERIMA KASIH

chapter 5 micro irrigation system. microirrigation basic concept

Documents

system of irrigation

irrigation methods

trickle irrigation

drip irrigation

microspray irrigation

volume of water

smaller sources of water

rate of water application