Soil moisture and EC sensors: choose the position before the dashboard

Start with the irrigation question

A grower wants to know whether water is reaching the root zone. Another wants to compare wetter and drier parts of the field. A probe beside one emitter can help with the first question, but it may give a misleading picture of the second. Write down the decision, the zone being represented and who will inspect a surprising reading. The first pilot should make that relationship clear before adding a large number of devices.

Record where the probe is, not just its coordinates

Include depth, soil or substrate, distance from the emitter and the local irrigation arrangement. Avoid positions chosen only because mounting or radio reception is convenient. Review sensor contact and installation against the exact model’s instructions; disturbed soil or poor contact can affect readings. METER’s TEROS manual is one reference that distinguishes mineral soil and soilless-media calibration. Use the documentation for the proposed probe, including any calibration needed for your medium.

Name the conductivity measurement precisely

Conductivity describes an electrical property, and the measurement method matters. The TEROS reference distinguishes bulk EC from pore-water EC and saturation-extract EC. A bulk reading can change with water content as well as the conductive material in the soil. Keep the reported method, unit and any conversion in the point list. A field EC number alone should not be treated as a direct fertilizer prescription or compared with a laboratory value obtained by a different method.

Use the first irrigation cycle to check the setup

Watch the reading before, during and after an irrigation event, while recording the event’s timing and any rain. Ask whether the change fits what the site team observed. If several depths are monitored, label them clearly rather than averaging them into one unexplained number. Keep missing data visible. A quiet graph could mean stable conditions, a disconnected sensor or a placement that does not see the wetted zone.

• Keep a photo and installation note for every probe.
• Label depth, measurement method and units in the platform.
• Record irrigation and rainfall events beside the trend.

Match the sensor interface to the field node

Soil probes may use analog, RS485, SDI-12 or a manufacturer-specific wireless interface. Check the actual protocol, supply, cable and logger support. For Modbus, obtain the register definitions and scaling; for wireless sensors, check the payload decoder and reporting schedule. Do not assume that every probe measuring the same parameters produces the same data. Include the full list of probes when calculating battery or solar power.

Expand by zone rather than by an arbitrary sensor count

After the initial placement has produced useful readings, compare the areas that differ in soil, slope, irrigation or crop management. Decide which differences require another point. Share a sketch of those zones, intended measurements and the irrigation system with the selection team. We can help compare sensor and communication options while the grower or agronomy team defines the crop-specific interpretation and action thresholds.

Common questions