Choose a soil-moisture sensing approach before requesting quotes

A soil-moisture purchase starts with the decision the farm needs to make. Volumetric water-content sensors estimate how much water occupies a volume of soil. Tension or matric-potential sensors indicate how tightly soil holds water. University of Minnesota Extension describes both as irrigation-scheduling approaches with different operating ranges, costs, and interpretation limits. Neither measurement turns into an irrigation instruction without a site-specific trigger and field context.[1]

Write the operator question first: is the farm estimating root-zone depletion, watching how hard roots must pull, checking whether water moved through a profile, or documenting a condition for a remote irrigation decision? That question determines whether a point sensor, profile probe, manual reading, or logged system belongs in the first shortlist. It also prevents a feature comparison from deciding the measurement method by accident.[1]

A sensor-only price is not a system price. A useful quote request separates the sensing element from the logger, gateway, communications plan, telemetry or software subscription, power, installation, training, maintenance, and support. Minnesota Extension lists separate sensor and data-logger costs for several measurement types, which is why a low component price cannot establish the cost of a deployed monitoring system.[1]

Ask whether the intended logger accepts the sensor's actual output and power requirements. For example, METER lists DDI serial and SDI-12 output for the TEROS 12. IRROMETER offers SDI-12 and 0 to 3 V adapter paths for WATERMARK sensors. Acclima lists its TDR-315N as an SDI-12 product. Sentek lists RS232, RS485, SDI-12, and Modbus paths for Drill & Drop configurations. Those statements describe vendor interfaces, not proof that any particular farm controller, cable run, or subscription will work together.[2][3][4][5]

A point water-content sensor can suit a farm that needs repeated readings at chosen depths. METER describes TEROS 12 as a capacitance sensor that reports volumetric water content, temperature, and bulk electrical conductivity; its page lists SDI-12 support. Acclima describes the TDR-315N as a digital TDR sensor with SDI-12 output. These are examples of point measurements, not a finding that one performs better in a particular soil.[2][4]

A tension-oriented system can suit a farm that wants to interpret the effort required to remove water from soil. IRROMETER describes WATERMARK 200SS as an electrical-resistance sensor for soil-water tension and lists a 0 to 200 centibar range. A profile probe can suit a different question: Sentek describes Drill & Drop configurations from 30 to 120 centimeters, with measurements at intervals along the probe. Compare these system shapes against the required decision, soil conditions, installation method, and data workflow rather than treating them as substitutes with one common score.[3][5]

This editorial rubric applies the University of Minnesota Extension's guidance on representative placement, direct contact, measurement interpretation, and system costs to a procurement decision. Apply the same checks to every candidate and leave an item unresolved when the reviewed evidence does not establish it. A conditional shortlist is more useful than a score that hides a missing logger, subscription, export right, or installation constraint.[1]

This is desk research, not FarmHub hands-on testing. The table records manufacturer-published specifications and listed web prices, not a ranking, accuracy finding, or compatibility promise. A listed sensor price does not establish the cost of the logger, gateway, installation, telemetry, support, or the deployed system. The reviewed public pages did not establish availability, regional support, data ownership, API, export, retention, offline behavior, or FarmHub compatibility. Get a dated, configuration-specific answer from the supplier.[2][3][4][5]

Water content is commonly expressed as a decimal or percent. It becomes a root-zone depletion estimate only when it is combined with layer thickness, field capacity or available-water assumptions, crop stage, and management allowable depletion. Tension rises as soil dries, but a threshold must be fitted to the crop, soil, depth, and observed stress response. A profile can show movement through depths, but a lower-depth response alone does not prove application efficiency or drainage loss.[1]

Use a reading with the irrigation record, rainfall, crop stage, forecast risk, and field observation. Treat automated control as out of scope until the farm has verified the timestamp, channel mapping, crop and soil context, and its own local trigger. University of Minnesota Extension recommends using soil-moisture information with other scheduling tools rather than treating one reading as a complete irrigation instruction.[1]

For a uniform irrigated block where the manager needs root-zone depletion, a water-content measurement may be the first shortlist. TEROS 12 and TDR-315N are candidates because their manufacturers publish water-content-oriented measurement and stated interfaces. The next gate is whether the farm can establish representative placement, field capacity, a logger and power path, and a local depletion trigger.[1][2][4]

For a block where the concern is how hard plants must pull for water, a tension-oriented system such as WATERMARK 200SS may be a candidate. The manufacturer-published range and output paths do not establish the trigger. The farm still needs a soil- and crop-specific threshold, a plan for temperature and salinity effects, and a check that the reader and logger represent the installed sensor.[1][3]

For a deep-rooted or variable block where the manager must see whether irrigation reached several depths, a profile probe such as Drill & Drop may be a candidate. Decide which intervals represent the managed root zone, how the bore preserves contact, and who interprets lower-depth movement. If the system cannot export data, retain records offline, or identify stale telemetry, it does not yet meet the decision need.[1][5]

Poor contact, an oversized hole, soil disturbance, unrepresentative placement, sensor or cable damage, power loss, communications loss, stale data, and a wrong channel-to-depth mapping can imitate a moisture change. Salinity, temperature, texture, bulk density, and soil-specific calibration can also change how electrical or dielectric measurements should be interpreted.[1]

This is FarmHub's conservative operational guidance, inferred from the installation, placement, and interpretation limits above. Stop using a reading as a trigger when the timestamp is stale, the value is implausible, a trace changes without a matching irrigation or weather event, expected depth responses are missing, or it conflicts with a checked field observation. Preserve raw data, event record, power and communications state, and installation note. Then determine whether the problem is placement, sensor condition, logger mapping, telemetry, or the irrigation assumption.[1]