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14 REFILL LIMITS
It is important to distinguish between the default calibration of the sensors and the
setting of upper and lower readily available water limits for each probe after
installation.
(This will be covered in detail in the agronomy principles section).
Once the probe is installed, you need to calibrate the readings obtained from the
probe against relative soil moisture content.
In essence, a depletion curve is derived
and by monitoring one or several typical wetting-drying cycles, an upper and lower
“refill” limit is obtained. If the service has been requested, then this function is
usually performed by a contracted agronomist.
The adjacent graphs are examples of a typical depletion cycle which has been
implemented after first having recorded how the farmer was irrigating as a standard
practice. The first graph shows the separate depth levels or data from sensors
positioned at various depths. The second graph is the combined result of all the
selected sensors for a specific probe.
Figure 13: A typical separate level graph showing a depletion cycle
