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To List Members: In considering installation and calibration methods for the HydroTek sensor, it has become apparent that a single data sheet will not suffice. Possibly, a single, meticulous calibration procedure will not even suffice. Because soil moisture sensors cannot differentiate between soil and air, volumes which can be occupied by water depend on compaction. Any activity which disturbs compaction will probably alter the concentration of water. Sensor geometries can be developed to minimize this disturbance, but will probably never be small compared to the geometries of disturbance. Presently, I am of the opinion that truly accurate results (better than 1%) can only be achieved by rigorously following an installation method designed specifically for the soil type at the installation, and then comparing the readings initially and periodically with laboratory evaluated samples for several seasons. After gaining confidence in a specific region with a particular sensor using specific methods, only then would I recommend unauthenticated placement and use. Of course, if only relative readings matter, i.e., for direct control applications, absolute calibration is not required as long as the sensor provides repeatable, monotonic readings which are uneffected by other factors such as temperature, somewhat beyond the range of interest. Then the irrigation system can be designed to be self calibrating with the sensors installed. M. G.