8
IRRIGATION WATER
IRRIGATION WATER
IRRIGATION WATER
IRRIGATION WATER
IRRIGATION WATER
The irrigation water must be checked regularly, especially in the
hydroponics industry. Conductivity is the most important parameter to
check since plants can be seriously damaged with too high a value.
Water used for irrigation has been classified in four distinct categories
depending on its conductivity:
Class I
Class II
Class III
Class IV
EC < 0.75 mS/cm
EC 0.75 - 2.50 mS/cm
EC 2.50 - 4.00 mS/cm
EC > 4.00 mS/cm
Class I: Any quantity of this type of water can be used without
limitation.
Class II: Only a limited quantity should be used depending on the
irrigation techniques and the crop.
Class III: May be used occasionally but for tolerant plants and/or
well-drained soils.
Class IV: To be used only if there is no other alternative and as little
as possible.
NUTRITIVE SOLUTIONS
The nutritive solutions constitute one of the most important factors in
determining the plant’s growth and yield. Hence, putting the right
solution at the plant’s disposal is indispensable to get the best result.
Conductivity (EC) of nutritive solutions must be checked regularly to
ensure that it agrees with the plant’s constitution. The plants also
have seasonal preferences, typically requiring lower concentrations in
the summer.
Asparagus
Watermelon
Carrot
Cabbage
Cucumber
Crysanthemum
1.50-2.00
1.50-2.50
1.50-2.00
2.00-3.00
2.00-3.00
1.50-2.50
PLANT
PREFERED EC VALUES
LIQUID PROBE
LIQUID PROBE
LIQUID PROBE
LIQUID PROBE
LIQUID PROBE
13
than 30°C, allow more time for the thermal equilibrium of the
system to be achieved.
• The meter provides for an LED alarm when measuring soil salinity.
If the LED is lit it means that the soil is too dry for a proper
measurement or it lacks nutritive substances. Wet the soil with a
moderate quantity of deminarilized water. Carry out the mea-
surement again and if the LED comes on, it means that in the soil
lacks nutritive elements (see page 5 for more details).
NOTE: Before any soil measurement, it is recommended that the tip
HI 76305 (soil probe) is rubbed with a fine sandpaper.
• After the measurement has been completed, the instrument can
be switched off, or it will automatically turn itself off after
approximately 2 minutes.
• The probes should be cleaned and dried (see "Probe Mainte-
nance" on page 14), after each measurement.
CALIBRATION
CALIBRATION
CALIBRATION
CALIBRATION
CALIBRATION
Calibration is not necessary for soil salinity tests.
PROCEDURE FOR WATER CONDUCTIVITY
• Pour sufficient quantity of a conductiv-
ity calibration solution (e.g. HI 7030)
into a beaker. If possible, use plastic
beakers (to minimize any EMC inter-
ference).
• Immerse the conductivity probe (approx.
5 cm/2").
H
I
7030
5 cm
(2“)
