Chapter VIII Automation

1
Chapter VIIIAutomation

Management of Drip/Micro or Trickle
Irrigation by Megh R. Goyal
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INTRODUCTION
Chapter VIII Automation

• Drip irrigation is an artificial method to apply
  essential water for plant growth that the nature
  has failed to provide.
• Methods of pressure irrigation
• sprinkler irrigation
• center pivot
• micro jets
• drip irrigation
• Management of Drip/Micro or Trickle Irrigation
• by Megh R. Goyal

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Chapter VIII Automation
INTRODUCTION

• Drip irrigation is the most efficient in terms of
  water use efficiency.
• In arid and semi-arid regions of the world
• High frequency control of drip irrigation has
  been automated.

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Advantages of Automation of Drip Irrigation
Chapter VIII Automation

• Economical
• Saving of manual labor
• Increase in crop yield
• Conservation of energy
• Effective control of irrigation

5
PRINCIPLES OF AUTOMATION
Chapter VIII Automation

• Irrigation programming considers several factors
• Time
• Duration and stage of crop growth
• Allowable plant water stress
• Soil aeration
• Soil water potential
• Soil salinity
• Management of Drip/Micro or Trickle Irrigation
• by Megh R. Goyal

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PRINCIPLES OF AUTOMATION The irrigation
controller
Chapter VIII Automation

• 1. Operates solenoid valves in sequence
• 2. Verify operation of
• - Pressure and flow rates

Management of Drip/Micro or Trickle
Irrigation by Megh R. Goyal
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Four methods for automation
Chapter VIII Automation

• 1. Soil moisture
• 2. Plant water stress
• 3. Estimation of evapotranspiration
• 4. Combination of one or more of these -
  
• methods

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Soil moisture method
Chapter VIII Automation

• 1. Successfully used for
  
  irrigation
  scheduling with the help of
• The tensiometers
• Heat transfer psychrometric methods
• Gypsum blocks
• Thermocouples

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Chapter VIII Automation
Soil moisture method

• 2. Microprocessors along with sensors are used to
  simplify the irrigation applications.
• 3. The sensors can provide
• Quick information to make decisions for
  application of irrigation depth.

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Soil moisture method
Chapter VIII Automation

• 4. A thermal method measures
• The matrix potential of soil.
• Soil temperature.

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Soil moisture method
Chapter VIII Automation

• 5. It is based on frequent measurements of
• ability of a porous ceramic sensor to
• dissipate a small amount of heat.

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Soil moisture method
Chapter VIII Automation

• 6. For a closed circuit automatic irrigation,
  the soil sensor is placed in the root zone.

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Soil moisture method
Chapter VIII Automation

• 7. For an automatic control of an irrigation
  system based on soil matrix potential, we need
  equipments for
• Automatic sampling from several sensors in
  sequence.
• Comparison of the readings of each sensor at
  which the irrigation begins at a predetermined
  matrix potential of the soil.
• The operation of irrigation controller to control
  the irrigation depth.

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Soil moisture method
Chapter VIII Automation

• 8. Desktop computers in combination with
  microprocessors have been successfully used.

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Water Content in the Plant
Chapter VIII Automation
Chapter VIII Automation

• 1. The water is frequently one of the limiting
  factors in the crop production.
• 2. Transpiration loss occurs from the plant
  surface due to an evaporative demand.

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Water Content in the Plant
Chapter VIII Automation

• 3. The majority of the plant growth processes
  suffer because of water deficit.
• 4. Probably, the cellular growth is most
  sensitive to water deficit.

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Water Content in the Plant
Chapter VIII Automation

• 5. There are several methods to estimate the
  condition of plant water.
• The determination of relative water content
• Diffusive conductivity of the plant.
• Water potential of the plant.
• Surface Temperature
• Management of Drip/Micro or Trickle Irrigation
• by Megh R. Goyal

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Water Content in the Plant
Chapter VIII Automation

• 6. Methods to measure the plant water stress
• The total leaf water potential with a leaf
  psychrometer.
• Temperature of leaf surface with an infrared
  thermometer.
• The leaf water potential indirectly on the basis
  of the diameter of the stem.

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Leaf Water Potential
Chapter VIII Automation

• The leaf water potential is measured by
  psychrometer or by adhering thermocouples to the
  leaves.
• Although the psychrometric measurements are taken
  routinely for research purpose, yet the
  instruments are expensive and not feasible for
  commercial use.

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Leaf Temperature
Chapter VIII Automation

• Measurements of leaf temperature can indicate
  status of a water stress.
• 2. Leaf temperature is measured with a
  non-contact infrared thermometer.
• 3. The measurements are sensitive to changes in
  the ambient temperature, interactions with soil
  and leaf area index.

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Stem diameter
Chapter VIII Automation

• 1. The diameter of the stem and the leaf water
  potential are closely related to one another.
• 2. The measurements of the stem diameter can be
  used for continuous recording of the stem growth
  and the condition of plant water.

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Stem diameter
Chapter VIII Automation

• 3. The periodic calibration of the changes in
  diameter of stem versus leaf water potential can
  be conducted for each phenological stage of a
  plant.
• 4. This technique can be used for the purpose of
  automation.

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Evapotranspiration (ET)
Chapter VIII Automation

• 1. To program irrigation, ET models have been
  successfully used throughout the world.

Management of Drip/Micro or Trickle Irrigation
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Evapotranspiration (ET)
Chapter VIII Automation

• 2. The following information is needed for ET
  estimations and the criteria to decide when to
  irrigate
• Evapotranspiration of a reference crop, potential
  ET, etc.
• Crop growth curve, crop coefficient and
  consumptive use of a crop.
• Index to estimate the additional evaporation from
  the soil surface when the soil surface is wet or
  dry.

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Chapter VIII Automation
Evapotranspiration (ET)

• Index to estimate the effect of soil water loss
  in relation to ET.
• Estimation of the available soil moisture used by
  a crop Consumptive water use.
• Relation between expected crop yield and crop
  water use.

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Direct Measurement of Essential ET
Chapter VIII Automation

• 1. The weighing lysimeter can serve as a guide to
  provide an adequate irrigation depth for the crop
  need.
• 2. The Etc can be used to program irrigation
  automatically.

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INSTRUMENTATION and EQUIPMENTS
Chapter VIII Automation

• 1. The automation of a drip irrigation system at
  a given pressure can potentially provide an
  optimum crop yield and optimum water use.
• 2. An automated irrigation system uses sensors to
  measure variables, such as
• Depth and frequency of irrigation.
• Flow rate
• Operating pressure.

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INSTRUMENTATION and EQUIPMENTS
Chapter VIII Automation

• Environmental conditions such as
• Wind speed.
• Ambient temperature.
• Soil moisture.
• Solar radiation.
• Rain fall.
• Leaf temperature, etc.

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INSTRUMENTATION and EQUIPMENTS
Chapter VIII Automation

• 3. Instrumentation and equipments can be
  subdivided in six categories
• Controls.
• Valves.
• Flow meters.
• Filter.
• Chemical injectors.
• Environmental Sensors.

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Controls
Chapter VIII Automation

• 1. The controls receive feedback
  about the volume of water for
• Field
• Pressure in the line
• Flow rates
• Climatic data
• Soil water
• Plant water stress

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Controls
Chapter VIII Automation

• 2. The controls can be operated automatically or
  manually
• Volumetric valves.
• Hydraulic valves.
• Fertilizer or chemical injectors.
• Flushing of filters.

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Valves
Chapter VIII Automation

• 1. Automatic valves are activated
• Electrically.
• Hydraulically.
• Pneumatically.

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Valves
Chapter VIII Automation

• 2. These are used to
• Release or to stop the water in the lines.
• Flush the mains and laterals.
• Continue the water from one field to another
  field.
• Regulate flow or pressure in main, submain or
  lateral lines.

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Chapter VIII Automation
Figure 2. Hydraulic valve.
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Chapter VIII Automation
Figure 3. Automatic metering valve along with a
hydraulic valve
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Chapter VIII Automation
Figure 4. Automatic irrigation controller (Rain
Bird).
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Chapter VIII Automation
Figure 5. Fertilization and irrigation programmer
for six different valves (for green house or
field)
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Chapter VIII Automation
Figure 6. Automatic controller (Nirim
electronics) for sequential irrigation using a
digital counter.
39
Chapter VIII Automation
Figure 7. Automatic controller (Nirim
electronics), using a programmer with a
perforated tape or card.
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Chapter VIII Automation
Figure 9. Bermad Automatic volumetric valve.
Management of Drip/Micro or Trickle Irrigation
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Flow Measurements
Chapter VIII Automation

• The flow metering equipments can deliver a
  predetermined volume and rate of water.

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Flow Measurements
Chapter VIII Automation

• Flow metering valves are of
• Propulsive type.
• Turbine type.
• Usually these meters are calibrated to measure
  applied volume of water or to measure the flow
  rate.

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Environmental Sensor
Chapter VIII Automation

• 1. Various types of instruments are available to
  determine the soil moisture
• Tensiometers.
• Gypsum blocks.
• Heat dissipater sensor.
• Soil psychrometer.

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Environmental Sensor
Chapter VIII Automation

• 2. Climatic Instruments
• Weather Station.
• Automated evaporation tank.
• 3. Plant water stress or leaf temperature of
  crop
• Leaf psychrometer.
• Porometer for stomate diffusion.
• Infrared and sensorial thermometer.
• Stem diameter sensor.

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Environmental Sensor
Chapter VIII Automation

• 4. The sensor can be used as a feedback for the
  management of irrigation
• If the soil at a particular field station is wet,
  the sensor opens the circuit of the hydraulic or
  solenoid valve and this station is bypassed.

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Filter
Chapter VIII Automation

• 1. The obstruction in the drippers caused by
  clogging agents (physical, chemical or
  biological) is a common problem and is considered
  a serious problem in the maintenance of the drip
  irrigation systems.
• 2. The suspended solids may finally clog or
  reduce the filtration efficiency.
• 3. The automatic flushing is available for
  different types of filters.

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Filter
Chapter VIII Automation

• 4. The flushing is done by means of backflow of
  water, thus allowing the water to move through
  the filter in an opposite direction.
• 5. This will depend on the type of the filter and
  and the accumulated solids.

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Chemical Injectors
Chapter VIII Automation

• The chemigation methods to inject the
  fertilizers, pesticides and other inorganic
  compounds are
• Pressure differential.
• Venturi meters.
• Injection Pumps.

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Chemical Injectors
Chapter VIII Automation

• In all the cases, digital flow meters can be used
  for chemigation by allowing a known amount of
  chemicals in a known amount of water to maintain
  a constant concentration of chemicals in the
  irrigation water.

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AUTOMATIC SYSTEMS
Chapter VIII Automation

• 1. Sequential hydraulically operated system.
• 2. Sequential System Operated electrically or
  operated hydraulically-electrically.
• 3. Non-sequential system electrically operated
  with or without programation, with the
  possibility of using information of the field.

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Sequential hydraulically operated system
Chapter VIII Automation

• 1. This system controls the valves in sequence.
• 2. The pressure arrives at the valve by means of
  a flexible hydraulic tube to provide a required
  pressure.
• 3. The diameter of the tube is generally between
  6-12 mm.

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Sequential hydraulically operated system
Chapter VIII Automation

• 4. Some hydraulic systems can be connected to the
  main valve of the line or to the system that
  replaces the water.
• 5. Electrically operated system activates the
  pump and deactivates it when the irrigation is
  over.

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Sequential hydraulically operated system
Chapter VIII Automation

• 6. The sequential hydraulically operated system
  is controlled by a predetermined amount of water.
  

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Normal Flow
Chapter VIII Automation

a. Normal Flow Figure 10. Flushing of automatic
filters by inverse or back flow.
Management of Drip/Micro or Trickle Irrigation
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Back Flow
Chapter VIII Automation
b. Inverse Flow Figure 10. Flushing of automatic
filters by inverse or back flow.
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Chapter VIII Automation

• Sequential hydraulically operated system
• The hydraulically sequential system can be used
  to irrigate
• Green houses.
• Gardens.
• Nurseries.
• Fruit orchards establishing low flow rates
  through tubes of small diameter.
• Flow rates in any diameter of tube.

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Chapter VIII Automation

• Sequential hydraulically operated system
• The system includes
• Automatic metric valve.
• Hydraulic valve.
• Hydraulic tube.

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Sequential System Operated electrically or
operated hydraulically-electrically
Chapter VIII Automation

• 1. These supply an electrical current through
  cables for the remote control of the valves
• 2. The current from the control panel to the
  valves, usually passes through a step down
  transformer to supply a voltage of 24 V.
• 3. The regular solenoid valves are mainly used
  for low flow rates.

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Sequential System Operated electrically or
operated hydraulically-electrically
Chapter VIII Automation

• 4. For pipes of larger diameters, the solenoid
  valves are used only as controls to activate the
  hydraulic valves and all the automation process
  is hydraulically-electrical.
• 5. The control of the second valve is always
  hydraulic.

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Chapter VIII Automation
Figure 11. Sequential hydraulically operated
system for green houses, gardens, nurseries and
fruit orchards. .
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Chapter VIII Automation
Figure 12. Electrically operated tensiometer and
solenoid valve.
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Programming irrigation with solenoid valves
Chapter VIII Automation

• The solenoid valves can be used to program the
  irrigation.
• 2. In order to calculate the crop water use, a
  computer program can be used with the information
  such as
• Use of crop water
• The soil moisture
• Evapotranspiration rates
• Date of the next irrigation
• The amount of water to be applied

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Programming irrigation with solenoid valves
Chapter VIII Automation

• 3. The ET models use crop and climatic
  information such as
• Crop coefficient
• Root zone depth
• Allowable depletion
• Drainage rates

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Programming irrigation with solenoid valves
Chapter VIII Automation

• 4. Climatic Information
• Temperature.
• Radiation.
• Precipitation.
• Constants used in evapotranspiration equations.

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Programming irrigation with solenoid valves
Chapter VIII Automation

• 5. Actual field data after the irrigation can be
  helpful to compute the infiltration and immediate
  drainage for correction of an estimated soil
  moisture.
• 6. The rate of computed ET can be used to
  indicate the required amount of irrigation or to
  specify the time for irrigation interval
• 7. This method is more practical for drip
  irrigation than for other irrigation methods..

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Automatic valves
Chapter VIII Automation

• 1. The automatic valves are commonly used for the
  pump house and filters for regulating the
  pressure in the main line to control the
  flushing cycles in the filters, or to control the
  volume of water through the secondary or lateral
  lines..
• 2. The solenoid valves can be used in the
  secondary or lateral lines to control the volume
  of water to the individual plots.

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Automatic valves
Chapter VIII Automation

• 3. The primary function of a solenoid valve is to
  switch on or switch off the system.
• 4. Automatic control valves can also be equipped
  with manual valves for better efficiency.
• 5. Automatic valves require periodic maintenance
  for a satisfactory operation.

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Automatic valves
Chapter VIII Automation

• 6. The maintenance program depends on the use of
  valve and the flushing operations.
• 7. It is important to clean the deposits on the
  stem of the valve.

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Chapter VIII Automation

• Automatic valves
• 8. A number of auxiliary controls can be adapted
  to the diaphragm valves to provide flexibility
  and convenience
• a. Control to reduce the pressure
• This valve responds to changes in the pressure at
  the exit of the main valve and adjusts to the
  pressure in the cap or valve cover to compensate
  for any change. A trouble in the operation can be
  caused by contamination, obstructions, incorrect
  assembly, damage or worn out parts.

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Automatic valves
Chapter VIII Automation

• b. Pressure regulator valves
• These valves are used to separate the system from
  the pressure in the main line. These must be open
  during the normal operation.
• c. Controls to adjust the velocity of the main
  valve
• These are small adjustable controls in the pilot
  control system. These regulate the speed of
  opening and closing of the main valve by blocking
  or strangling the flow that enters or leaves the
  casing. These can be subjected to obstructions by
  fine sediments if tightly fit.

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Chapter VIII Automation
Automatic valves

• Controls
• 1. Several electromechanical and electronic
  controls in the drip irrigation system are
  automated.
• 2. The controls with mechanical time clocks open
  and close only a single valve at one time.
• 3. Many controls are available also to diagnose
  operation and identify the troubles and to take
  remedial steps.
• 4. Others put off the system during rainfall and
  restart the system when necessary.

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Chapter VIII Automation
Automatic valves

• The microprocessors and microcomputers, based on
  controls, also can be programmed using data of
• Tensiometers.
• Class A pan evaporation.
• Thermocouples.
• Soil moisture tension gages.
• Anemometer.
• Flow meter.
• Pressure transducer.

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Automatic valves
Chapter VIII Automation

• 5. These controls are based on the climatic and
  soil sensors or according to the program
  specified by the irrigator.
• 6. The data from the flow meters and pressure
  gages is used to
• Determine flushing time.
• Detect any troubles in the system.

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Chapter VIII Automation
Automatic valves

• 7. In most of the cases, the controller has a
  calendar programmer, so that the cycle of
  irrigation begins automatically on a particular
  day of the week and at a particular time of the
  day.
• 8. Practically all automatic controllers have a
  station selector on the outer surface of the
  panel.

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Automatic valves
Chapter VIII Automation

• 9. This station selector shows a green light to
  show the station in operation. In addition, it
  can also be set manually so that the irrigation
  operator can start and put off whenever desired.

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Sequential System Electrically Operated
Chapter VIII Automation

• 1. In these systems, the amount of water
  distributed to the different blocks is determined
  by a flow meter.
• 2. A timer determines the duration of operation
  fourteen (14) days and twenty-four (24) hours per
  day.

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Sequential System Electrically Operated
Chapter VIII Automation

• 3. These can be activated by sensors based on
  tensiometers or class A pan evaporation.
• 4. Although this type of system was developed
  mainly for green houses, yet it can be used for
  drip irrigation.

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Non-sequential system
Chapter VIII Automation

• 1. These systems are completely automatic and are
  controlled electrically.
• 2. These non-sequential systems are controlled by
  hydraulic or electrical valves that can operate
  the valve in the desired block at random, and can
  supply known amount of water for a known duration
  to a desired block.

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Non-sequential system
Chapter VIII Automation

• 3. Each unit can supply a known flow at different
  hours during the day, in response to soil
  moisture status in each block.
• 4. The Control Panel consists of electrical
  circuits that operate the pump, main valve, adds
  fertilizer according to a pre-established
  schedule and measures the soil moisture to
  estimate the crop irrigation requirements.

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Non-sequential system
Chapter VIII Automation

• 5. Such systems usually operate by a remote
  control system and are designed to provide
  feedback of field data, so that the automatic
  adjustment can be made and adjustments for
  changes in pressure and flow rates can be made to
  the discharge flow in the distributing lines.

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Central Panel
Chapter VIII Automation

• The central panel allows to control all the
  operations of the field, sending instructions to
  the valves and receiving continuous data on the
  operation of system. It consists of a programmed
  unit of irrigation, a unit for transmission of
  information, a unit for the control of flow in
  the laterals and a unit for warning signals.

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Chapter VIII Automation

• Field Panel
• The field panel is placed centrally in the field
  and operated by remote control unit. The signals
  of main panel are sent by an individual
  communication channel and these are transmitted
  to individual field panel. The field panel can
  collect the data on water meters, operating
  pressures and warning signals. Then the data can
  be transmitted to the main panel (control panel).

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Use of Sensors to Program Irrigation
Chapter VIII Automation

• In addition to the above mentioned instruments,
  sensors are available to determine the soil
  moisture tension or the soil moisture.
• 2. Tensiometers and gypsum blocks are simple and
  economical to use.
• 3. Another method is neutron scattering method
  but it is quite expensive and is only for
  research purpose.

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Use of Gypsum blocks and Tensiometers
Chapter VIII Automation

• 1. The gypsum blocks can measure the soil
  moisture tension in the range of 1-15 atm.
• 2. The precision of this method is based on the
  temperature, salt concentration in the soil
  solution, physical characteristics of the gypsum
  block and the electrical resistivity of the soil.
  
• 3. For tensions of 2-80 cbars, a tensiometer is
  recommended instead of a gypsum block.

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Use of Gypsum blocks and Tensiometers
Chapter VIII Automation

• 4. Tensiometer (Figures 13 to 15) measures the
  tension and the reading is given in cbars.
• 5. The main disadvantage of tensiometer is a
  relatively low critical tension of 85 cbars
  after which the air enters into the plastic stem
  of a tensiometer.
• 6. The soil moisture by any method will show
  variations in the soil moisture within the same
  field.

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Chapter VIII Automation
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Chapter VIII Automation
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Chapter VIII Automation
Figure 16. Automatic unit for control of
irrigation based on the gypsum blocks (sensors).
Management of Drip/Micro or Trickle Irrigation
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Neutron Scattering Method
Chapter VIII Automation

• 1. The neutron disperser consists of a neutron
  radiation source of high energy and a neutron
  detector.
• 2. The use of the neutron scattering method
  requires the installation of access tubes at the
  beginning of planting and removal of these tubes
  after the last harvest.

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Neutron Scattering Method
Chapter VIII Automation

• 3. It is recommended to install one sensor at
  each 30 cm depth. Periodically the operator will
  obtain the readings of the tube at the desired
  depth.
• 4. The readings can be recorded automatically and
  are stored in the memory of the neutron
  scattering panel.

Management of Drip/Micro or Trickle Irrigation
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Class A Pan Evaporation to Automate the System
Chapter VIII Automation

• The relationship between pan evaporation and the
  water loss have been well established, both are
  exposed to similar climatic conditions in the
  same field.

Management of Drip/Micro or Trickle Irrigation
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Preventive Maintenance
Chapter VIII Automation

• Preparation after the Last Harvest
• 1. Clean the controllers, valves and sensors.
• 2. Examine the condition of the control panel and
  store it well.
• 3. Remove and store batteries.

Management of Drip/Micro or Trickle Irrigation
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Preventive Maintenance
Chapter VIII Automation

• 4. Flush and drain the hydraulic tubes.
• 5. Disconnect the electrical wires in the field
• 6. Examine for possible breakage and defects in
  electrical conductors.

Management of Drip/Micro or Trickle Irrigation
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Preparation for the start of a crop season
Chapter VIII Automation

• 1. Be sure that all the electrical connections
  are cleaned and adjusted well the electrical
  contacts are free of corrosion and dirt.
• 2. Inspect all the hydraulic lines and pneumatic
  lines for leakage or breakage.
• 3. Verify that the equipments, accessories and
  sensors operate properly.

Management of Drip/Micro or Trickle Irrigation
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During the Crop Season
Chapter VIII Automation

• 1. Visually examine all external components
  weekly
• 2. Disconnect the electrical wires in the field
  during electric storms.
• 3. Disconnect the batteries when the control is
  out of service for one week or more than one week.

Management of Drip/Micro or Trickle Irrigation
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Positive Thought
Chapter VIII Automation

• Its quite simple One sees clearly only with
  the heart. Anything essential is invisible to the
  eyes. . .
• 
  Antoine De Saint-Exupery

Management of Drip/Micro or Trickle Irrigation
by Megh R. Goyal