Product Manual

14
unsuspected run off or subsoil drainage. Radical reduction or even discontinuance of irrigations in the
lower sections during some periods often results in material saving in water and at the same time
maintains better soil moisture content for crop growth.
In soils containing rock or gravel, frequent soil sampling is often either impractical or the cost is
prohibitive, yet these are the soils where irrigation control is needed most. They dry out quickly in hot
weather and to ensure adequate moisture, much water is often wasted to deep percolation by
“guesswork” irrigation. Charting IRROMETER readings frequently – even daily – often results in
material water savings and in better soil moisture conditions for plant growth.
In many cases, the value of IRROMETER control goes far beyond cash savings on the monthly water
bill. It makes a limited supply of water go farther and thus saves the investment required for developing
new sources of supply.
Common Questions
The following are answers to questions that sometimes arise when IRROMETERS are used for the
first time.
INSTRUMENTS ALWAYS READ ZERO
Soil is saturated from irrigation, rainfall or poor drainage.
Instrument has no water or lost suction due to low water level in the IRROMETER. Refill
IRROMETER.
Check gauge calibration and fill the IRROMETER (gauge should read 80-85 with vacuum applied by
hand vacuum pump, less with LT, MLT).
INSTRUMENTS DO NOT SEEM TO
RECORD TRUE SOIL MOISTURE CONTENT
This is by far the most common question. Almost invariably it is due to the fact that actual soil
moisture content is very different from what you thought existed. Taking soil samples within about 6”
of an IRROMETER station and at the exact depth of the ceramic tips with a soil tube auger or shovel
will usually demonstrate the instrument readings are accurate. Refer to the sections on “GAUGES”
and “CERAMIC TIPS” on page 17.
INSTRUMENTS REQUIRE FREQUENT REFILLING
This usually indicates under-irrigation – readings in the upper range for periods of several days. Other
occasional causes may be:
Improper installation – soil not properly packed around the instrument.
A leaky seal at the closure. Replace rubber stopper if it has hardened.
A leaky gauge connection.
INSTRUMENTS RESPOND SLOWLY TO IRRIGATIONS
This is usually due to a slow infiltration rate of the particular type of soil.
Make sure that the instrument is full of fluid and free of air. See section on “FIELD SERVICING” on
pages 8-9.
Ceramic tips partially sealed with salts. See section on “CERAMIC TIPS” on page 16.
Gauge movement “sticky” due to minor damage. Tap the gauge lightly before taking readings.
If IRROMETERS are several years old or tip has been frequently dried by removing from the soil,
factory reconditioning the IRROMETER is desirable. For a nominal cost, the IRROMETER tip,
stopper and cap is replaced. The IRROMETER is returned to you as new.
WIDE VARIATIONS IN RATE OF CHANGE OF INSTRUMENT READINGS
This is to be expected. Almost all new users discover amazing variations in soil moisture content in
different sections due to topography and different soil types. That is the reason that an adequate
number of instruments is necessary for reliable irrigation control. Attempting to control irrigations on
the basis of inadequate information can be misleading rather than helpful.