Great men are they who see that spiritual thought is stronger than any material force, that thoughts

1
Great men are they who see that spiritual
thought is stronger than any material force, that
thoughts rule the world -Ralph Waldo Emerson -
Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
2
The fluid that give us the life, the
water.-Anonymous-
Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
3
Chapter V The tensiometer Use, installation
and maintenance
Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
4
Chapter V The tensiometer-Use, installation and
maintenance

• OBJCTIVES
• What is a tensiometer?
• Preparation, calibration and installation
• How does the tensiometer work?
• Maintenance and storage
• Limitations
• Trouble shooting

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• INTRODUCTION
• For an efficient irrigation system, it is
  necessary that water quantities are available for
  the plants during the crop season and precise
  measurements of soil moisture are conducted.
  Plants require a specific amount of moisture in
  the root zone. During the irrigation process,
  quantity of water application must provide for
  the amount of moisture needed by the soil.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• What is a tensiometer?
• A tensiometer indicates the tension with which
  the water is adhered to the soil particles.
• It is a relative and indirect method to indicate
  if the soil has sufficient available moisture for
  the plant growth.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Types of tensiometers

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Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Types of tensiometers

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Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Types of tensiometers

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Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
10
Chapter V The tensiometer-Use, installation and
maintenance

• Types of tensiometers

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Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• How does the tensiometer work?
• The tensiometer should be correctly inserted in
  the soil. After the tensiometer has been properly
  installed, the water in the plastic tube comes in
  contact with the water retained in the soil pores
  through a ceramic tip, that lets a flow of water
  in both directions until the equilibrium is
  reached.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Parts of a tensiometer
• Plastic tube It provides rigidity for the
  instrument and protection for the measure
  mechanisms.
• Porous ceramic tip Allow the water from the
  soil to move inside and out of the instrument.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Parts of a tensiometer
• Reservoir cup It provides space for the storage
  of water to substitute the one lost through the
  porous tip.
• Vacuum gage It indicates the vacuum or suction
  that occurs inside the tensiometer due to water
  movement across the porous ceramic tip by showing
  readable values.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Figure 1A. Principal components of the
  tensiometer.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Figure 1B. Principal components of the
  tensiometer.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Preparation and Calibration
• The tensiometer should be prepared before any
  installation in the field.
• Distilled water is used to fill the plastic tube
  and reservoir cup. Boiled water is also an option
  . Avoid the formation of bubbles.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Preparation and Calibration
• Fill the tensiometer with a water solution with a
  special conditioning green or blue dye.
• Keep the tensiometer submerged in clean water for
  few days before the actual installation . Again,
  fill the tensiometer with the solution (including
  the reservoir cap) and apply suction with the
  hand pump to remove the air bubbles and eliminate
  any partial vacuum.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Factors selecting soil depth and location for the
  installation
• Crop species and the depth of a root system.
• Soil type and variation.
• Natural surroundings and land topography.
• Type of an irrigation system.
• Desired level of control.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Figure 2. Selection of a location for the
  installation of a
• tensiometer.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Figure 3. The use of two tensiometers in a fruit
  orchard.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Location of a tensiometer
• Furrow Irrigation Tensiometer is installed on
  the inner side of the raised bed of a furrow, in
  crops planted in rows on the side of furrows .
  For fruit trees irrigated by ditches, two
  tensiometers are installed One at the side the
  tree facing the noon sun and the second
  tensiometer at a distance of 30 to 45 cm from the
  furrow.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Location of a tensiometer
• Overhead (Sprinkler) irrigation Tensiometers
  should be installed at a location where the plant
  receives afternoon sunlight. The location must
  not be covered with branches of a tree and should
  not be located at the lowest point with
  accumulation of runoff. The tensiometer should
  not be installed too close to the irrigation line
  or a sprinkler. For fruit trees, two tensiometers
  should be installed between two trees down the
  row. For row crops, the tensiometer should be
  installed at the bed of a planted crop.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• LOCATION OF A TENSIOMETER
• 3. Drip irrigation In fruit trees,
  tensiometer should be placed on the sunny side of
  the tree. In newly planted fruit trees, the
  shallow tensiometer should be located near the
  root zone. The row crops require tensiometers
  down the row.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Figure 4. The tensiometer at inner side of a
  furrow.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• INSTALLATION
• There must exist a good contact between the
  ceramic tip and the soil.
• The size of the hole needed to insert the
  tensiometer into the soil should be of diameter
  equal to that of a tube of the instrument.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• INSTALLATION
• 3. The hole is dug with a galvanized iron pipe up
  to a desired depth to install the tensiometer .
• 4. It is desirable to leave a space of 2.5 cm
  between lowest part of a gage and the ground
  surface. This allows free expansion and
  contraction of the diaphragm of the gage.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• INSTALLATION
• 5. At ground level, some loose soil is placed
  around the plastic tube and is pressed lightly so
  that runoff water does not enter into a space
  between the tube and the hole.
• 6. After installation, fill up the reservoir
  compartment with a solution made up of distilled
  water and a blue dye.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• INSTALLATION
• 7. Remove air bubbles from the reservoir
  compartment and plastic tube.
• 8. A good extraction of air increases the
  sensitivity of tensiometer and the accuracy of
  reading. Wait at least two days until the
  instrument reach equilibrium with soil water.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Readings of a tensiometer
• The best time of the day for reading the
  tensiometer is early in the morning.
• At this time, the water movement between the soil
  and the plant is at a minimum level because of a
  state of equilibrium.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Readings of a tensiometer
• Readings should be taken at the same hour on a
  regular basis. Frequency of readings depends on
  the crop, soil and climatic conditions and the
  irrigation method.
• Larger is the interval of irrigation, lesser is
  the frequency of readings.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Readings of a tensiometer
• Tensiometer should be read daily for plants with
  shallow roots and for drip irrigation.
• In sandy soils and hot climates, and for other
  irrigation methods, the readings are taken three
  times a week.
• In moderate climates, one reading a week is
  enough.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Readings of a tensiometer
• Before taking the readings, lightly tap the
  vacuum gage. A quick movement of the needle will
  tell if the soil is drying or receiving moisture.
  
• Readings must be taken always before servicing
  the instrument.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Readings of a tensiometer
• 10. The use of the tensiometer is most efficient
  when the data is copied on graph paper and
  the curve is drawn. The curve describes the
  tendency of crop water use.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Figure 5. Graph paper for recording tensiometer
  readings.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Interpretation of the Readings
• Near saturation (2 10 cb) Soil stays close to
  saturation on an irrigation day and a few days
  later.
• Field capacity (11 20 cb) Irrigation must
  stop in this interval to prevent water loss by
  deep percolation and loss of nutrients.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Interpretation of the Readings
• Irrigation interval (30 60 cb) Usual interval
  to initiate the irrigation. At these intervals
  assures that soil water will be available to the
  plant.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Interpretation of the Readings
• Dry (60 70 cb) The stress interval. Crops are
  not necessarily under water stress. In some
  soils, water is available for the plant but is
  not enough.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Interpretation of the Readings
• Breakage of tension (80 cb) This is the limit of
  precision of the tensiometer. Readings over 80
  are possible but the tension breaks the water
  column between 80 and 85 cb.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Automation of an irrigation system
• The tensiometers are sensors in an automatic
  irrigation system.
• These instruments are inserted in the soil at a
  specific depth depending on crop type, soil and
  irrigation method.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Automation of an irrigation system
• Each tensiometer includes an electrical conductor
  that converts measurement of the soil tension
  into an electrical signal.
• This signal is received by a control panel, which
  operates a solenoid valve to regulate the flow of
  water from the system to the field.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Advantages of an automatic irrigation
• a. Better control of quantity and frequency of
  irrigation.
• b. Money is saved since no labor is needed to
  open and close irrigation lines in the field.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Advantages of an automatic irrigation
• c. One does not have to visit the field during
  odd hours to allow the irrigation.
• d. It registers tendencies of water consumption
  with a system of automatic recording units.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Typical automatic irrigation

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Maintenance and service
• After installation, the instrument must be
  revised frequently and daily. Excess air is
  removed and then water is added to the reservoir
  cup.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Maintenance and service
• If the tensiometer is not serviced and maintained
  for a long period of time, then the water level
  in the reservoir is lowered significantly. It
  must be filled up again with water. Air bubbles
  must also be removed with a hand vacuum pump.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
46
Chapter V The tensiometer-Use, installation and
maintenance

• Maintenance and service
• Under saline conditions, maintenance is essential
  to keep the ceramic tip free of salts.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Vacuum hand pump
• This is an instrument to remove air from the
  tensiometer. It has a universal suction tip that
  adjusts itself to all models of tensiometer.
• Suction is applied to the tensiometer to create a
  vacuum and remove the air bubbles that make the
  readings less precise.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Figure 7. Vacuum hand pump.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Suction Method
• This method consists of placing the tensiometer
  inside a Matraz Erlenmeyer flask through a
  rubber plug.
• A know amount of suction is applied around the
  ceramic tip by opening a stopcock. The vacuum
  gage will show a reading corresponding to the
  applied suction.
• Then the suction valve is closed. If the reading
  of the instrument remains unchanged, then it
  implies that there is no loss of suction from the
  seal of the ceramic tip and the gage.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Figure 8. Suction method to test the operation of
  a tensiometer.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance

• Storage
• After crop season is finished, the tensiometer
  must be removed, emptied and stored.
• The ceramic tip never should be allowed to dry
  up. Immediately after removing it from the soil,
  cover the ceramic tip with a wet towel to keep it
  wet, while it is being packed.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
52
Chapter V The tensiometer-Use, installation and
maintenance

• Storage
• Wet packing is recommended for temporary packing.
  
• Dry packing is only recommended for long periods
  of time.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
53
Chapter V The tensiometer-Use, installation and
maintenance

• Limitations
• The tensiometer is filled with water and is
  limited by the physical properties of the water.
• The operational limit of the tensiometer is 80
  cbars at sea level.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
54
Chapter V The tensiometer-Use, installation and
maintenance

• Limitations
• Tensiometer with common vacuum gage does not
  respond quickly. A good precision is possible for
  changes in tension with tensiometer equipped with
  electric digital sensors.

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance
Trouble shooting

• The instrument always reads 2

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Chapter V The tensiometer-Use, installation and
maintenance
Trouble shooting

• The tensiometer does not indicate the correct
  tension

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
57
Chapter V The tensiometer-Use, installation and
maintenance
Trouble shooting

• Water needs to be replaced frequently

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
58
Chapter V The tensiometer-Use, installation and
maintenance
Trouble shooting

• Little response to the irrigation

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
59
Chapter V The tensiometer-Use, installation and
maintenance
Trouble shooting

• Wide variation in readings

Management of Drip/ Micro or Trickle Irrigation
By Megh Goyal
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Things must be done right although you fail, not
to do them wrong to see if they turn out
right.-Victor Pellot Power-