Watermark 900M Installation And Operating Instructions Manual

INSTALLATION AND
Model 900M – Monitor
Automatically Collects Soil Moisture Sensor Readings
The WATERMARK Monitor automatically reads up to eight (8) sensors and stores the readings for collection and
display by a computer. WATERMARK soil moisture, soil temperature, IRROMETER Model V and RSU (4-20mA
transducer), switch closure, voltage, rain gauge and 4-20mA sensors can be read and recorded (some require adapters).
SENSOR SITE SELECTION — Often more than one sensor should be placed at a given location, at varying depths; for
instance, one sensor in the upper portion of the plant's effective root zone and other sensors located deeper into the root
zone profile. It can give a better representation of the plant's uptake of water and is referred to as a 'sensing station'.
PLACEMENT
Furrow or Flood Irrigation – Locate sensing station about 2/3 the way down the run, just ahead of the tail or backup
water. This is the area where water penetration is usually the poorest. With tree crops, locate sensors on the
southwest side of the tree (in the Northern Hemisphere) as this side gets the hot afternoon sun.
Sprinkler Irrigation – Even though the distribution is typically more uniform with sprinkler irrigation, there can be
great differences in penetration and holding capacity due to soil variations, interfaces and contour. These variation
sites make good locations for sensor stations. With tree crops, locate sensors at the drip line of the canopy being
sure that they are not obstructed from the sprinkler's distribution. With row crops, locate sensors right in the plant row.
Center Pivot Irrigation – Place sensors at 4-5 locations down the length of the pivot (between towers) just ahead
of the 'start' point. Additional locations at 'hot spots' or good production areas of the field, can help give a better overall
view of the field. Be sure to use enough 'sensing stations'; every 10-15 acres is a good rule of thumb.
Drip or Micro Irrigation – Sensors must be located in the wetted area. With drip emitters this is usually 12"-18" (30-
45 cm) from the emitter. With micro-sprinklers, usually 24"-36" (60-90 cm) is best. Monitor often enough to get a good
overall picture of the field, or irrigation 'block', and consider the soil variations which exist. Keep in mind that light soils
dry very quickly and heavy soils more slowly.
DEPTH — This depends on the rooting depth of your crop, but can also be affected by soil depth and texture. With
shallow rooted vegetable crops, one depth may be adequate (root system less than 12" [30 cm]). With deeper rooted
row crops (small grains, vines and trees) you need to measure soil moisture in at least two depths. With 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 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. Always
install a wet sensor. If time permits, slowly wet the sensors by partially submerging them (no more than half way) in
water for 30 minutes in the morning, let dry until evening, wet for 30 minutes, let dry overnight, wet again for 30
minutes the next morning and let dry again until evening. Soak over the next night and install WET. 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 it will respond accurately. After 'conditioning' sensors are ready
for installation.
Sensors MUST be installed in an active portion of the root zone of the plant being monitored, either vertically or
up to a 45° angle. Using a 7/8" (22 mm) diameter bar (or 1/2" IPS pipe) or an IRROMETER Coring Tool or Slide
Hammer Tool, bore an access hole to the desired depth. Extract the bar, 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. In either
case, fill the bottom of the hole with a fluid mixture of mud made from soil removed from the hole and water, then
firmly push the sensor down into the mud at the bottom of the hole. Once this mixture dries, the sensor will have been
'grouted' in to ensure maximum surface contact between the sensor surface and the surrounding soil. Alternately, if
the soil is already adequately moist, the sensor can be firmly pushed to the desired depth as long as it is a tight
enough fit to ensure adequate contact. A snug fit is absolutely necessary. Backfill the hole firmly.
Before installation, the sensor can be attached to a 1/2" class 315 PVC (thin wall SDR 13.5) or 3/4" CPVC
(SDR 11) pipe with a transition solvent PVC to ABS cement. The pipe becomes a conduit to protect the sensor
wires. This also makes the sensor easier to push into the access hole and remove, if desired. The top of
INSTRUCTIONS
OPERATING
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