Product Manual

4
stop. 9. Tip (body) of instrument can be removed by pulling out from the top housing. Be sure to
remove the cap before attempting to pull the tip (body) out to avoid damaging the gauge. Replacement
tips (bodies) are available.
CAUTION for RSU — use the Test Pump service unit pump (with the gauge attached), as this model
IRROMETER does not have a gauge. With the model “RSU” carefully pull a vacuum to a reading of
80 to 85 for standard (white tip) IRROMETERS, 30 to 35 for LT (blue tip) IRROMETERS and 10 to 12
for MLT (miniature blue tip) IRROMETERS. Be very careful to bleed vacuum slowly. The transducer
diaphragm is very sensitive and can be damaged by a rapid release of vacuum or over-pumping.
Selecting Locations for Installation
Careful selection of key locations for installation is of utmost importance with IRROMETERS, as with
all other methods of soil moisture measurement. Except where there is very level, uniform soil and
subsoil and very uniform distribution of water
– as with sprinklers – do not install the
instruments in a “checkerboard” pattern.
Almost invariably such factors as
productivity in good and poor sections,
topography, infiltration rate and water
holding capacity of varying types of soil and
subsoil will govern the location of “stations”.
With furrow or basin irrigation, instruments
are usually placed near the lower end of the
run. In very long furrows, a second station of
instruments is sometimes installed at the
upper end or at some intermediate point in
the run.
If, after an irrigation cycle or two, the
appearance of the crop indicates that more
critical areas exist, either move some of the
instruments to these areas or install
additional instruments.
The IRROMETERS should always be
installed in the root zone of a vigorous plant
or tree. Also, where the plants are large
enough to shade part of the ground, it is
customary to install all instruments in locations on the sunny side of the plant where ground surface
evaporation losses are greatest.
When crops have a root system exceeding about 18", instruments should be installed at two depths
— one at about 25% of root zone depth and one at about 75% depth.
In making an initial installation, concentrate more instruments than you think will ultimately be
required in a relatively small area. Later, instruments can be moved to other areas if they are not
needed. Otherwise, leave instruments in permanent locations for the entire growing season, so there
will be continuity in the seasonal chart curves. Most of the value of the charts is lost when instruments
are moved. In starting out it is better to do a thorough job in a small area than to scatter a few
instruments over the entire acreage.
NOTE: Due to many infield variations of soil types, it is best to use two “locations” in a
single irrigation block. Then “average” the readings for a better overall picture.
Zone of moisture control
with two IRROMETERS.