deep, well-drained soils, crops will generally root
deeper – if moisture is available. With coarse, shallow
or layered soils, root systems may be limited in depth.
In general, sensors must be located in the effective
root system of the crop. Guidelines on proper depths
for specific crops and conditions can be obtained from
us as well as from your local farm advisor.
NOTE: Our recommendation for anyone using sensors
for the first time is to use an adequate number of
‘stations’ over a smaller area to begin with to get an
accurate picture. Then read them regularly over the
season to learn the patterns which normally develop.
SENSOR INSTALLATION — WATERMARK Soil
Moisture Sensors must be ‘conditioned’ prior to
installation. The sensors should be soaked to
saturation then dried fully twice, then soaked to
saturation again prior to installation. This ‘conditioning’
of the sensors ensures quick response to changing soil
moisture conditions. If a sensor is only soaked and
then installed, several irrigation cycles must pass
before the sensor will respond accurately. Soak the
sensors in a bucket of water for several hours to
saturate them. Hang them up overnight to dry
sufficiently. After ‘conditioning’ they are ready for
installation. Sensors MUST be installed WET in the
active root zone of plants that are typical of the area the
WATERMARKs monitor. Install either vertically or up to
a 45° angle. Bore a 7/8" (22mm) diameter access hole
to the desired depth, then insert the sensor. Be careful
to ensure a snug fit between the sensor and the
surrounding soil then backfill the hole firmly. The
access hole can be made by pounding a 7/8" (22mm)
diameter bar (or 1/2" [13mm] size IPS pipe) into the soil
or using a coring tool or IRROMETER Installation Tool
to the desired depth, then extracting the selected tool,
being careful not to disturb the soil surrounding the
borehole. With hard or rocky soil, a larger diameter
hole can be made with a soil auger. Mix the auger
cuttings with water to create a slurry and pour into the
borehole. Then insert the sensor into the hole. Once
the slurry dries, the sensor will have been “grouted” in
to ensure good contact with the soil. The sensor can be
attached to 1/2" (13mm) class 315 PVC (thin wall SDR
13.5) or 3/4" (19mm) CPVC (SDR 11) pipe with a
transition solvent PVC to ABS cement. The pipe
becomes a conduit to protect the sensor wires. Also,
this makes the sensor easier to push into the access
hole and remove, if desired. The top of this pipe section
7
should be capped or plugged so surface water does
not travel down to the sensor. Drill a small hole in the
side of the pipe just above the sensor to allow water to
drain away if it becomes trapped in the pipe. (See
‘IRROMETER Installation Tools’ for other options.) The
soil temperature sensor should be installed in the soil
near a representative soil moisture sensor. All the soil
moisture sensor readings per Node will be
compensated by the soil temperature sensor. Bore a
1/2" (13mm) diameter hole in the soil and insert the
temperature sensor then backfill the hole. Refer to
instructions that accompany all other sensors for
proper installation. The switch closure sensor is a
pressure gauge with a 1/4" NPT connection and an
adjustable switch mounted to its face. The gauge is
installed into the irrigation pipeline. The pressure range
of the gauge should be selected so that the normal
system pressure is in the middle third of the gauge
range. The normal system pressure is the set point
which will trip the switch, indicating that an irrigation is
taking place.
SENSOR WIRING — Additional wire can be added to
the sensors for long distances. Please adhere to the
following wire size recommendations when adding wire:
DISTANCE
WIRE SIZE
Up to 1000 ft. (300 m) . . . . . . . AWG UF 18 (1.02 mm, 0.82 sq mm)
1001 to 2000 ft. (600 m) . . . . . AWG UF 16 (1.29 mm, 1.31 sq mm)
2001 to 3000 ft. (900 m) . . . . . AWG UF 14 (1.63 mm, 2.08 sq mm)
Multi-conductor wire can be used and twisted pairs are
not necessary. All splices should be made with direct
burial type waterproof splices, Spears DBY
®
or similar.
Be sure to record each pair of sensor wires indicating
what type of sensor is attached and the placement
depth per Node.
NOTE: Videos describing the IRROmesh System and
how to install it are available from the
VIDEOS tab at:
www.IRROMETER.com.
MAINTENANCE — Keep all Node solar panel lenses
clean and clear of any shadows to ensure steady
charging. Monitor the presence of each Node and their
comparative current levels in the WEB display. Units
that ‘drop-out’ or have non-typical voltages likely need
to be inspected for shading or cleanliness.
All Nodes can be ordered from the factory with bird
deterrent covers or retro-fitted with the purchase of a
bird deterrent cap.