Multi-Layer Tubular Soil Moisture and Temperature Sensor

The JW-TRSQ(LC3) Multi-Layer Tubular Soil Moisture and Temperature Sensor is designed for continuous soil profile monitoring at multiple depths. It measures volumetric soil moisture and soil temperature through a sealed PVC tube and transmits each layer’s data through RS485 Modbus RTU.

Standard configurations include 3-layer, 4-layer and 5-layer soil monitoring, while customized measuring depths can be provided according to crop root depth, irrigation method and project requirements.

The tubular sensor is suitable for smart irrigation, open-field farming, greenhouses, orchards, pasture, drought monitoring, agricultural research and water conservancy projects. Its IP68 sealed structure allows long-term vertical installation below ground without exposing metal sensing electrodes directly to soil.

Explore more soil sensors for agriculture and environmental monitoring or contact JW-IoT for layer and depth selection.

What Is a Multi-Layer Soil Moisture Sensor?

A multi-layer soil moisture sensor measures soil conditions at several depths with one vertically installed probe.

A conventional single-point sensor provides data from one local depth. A multi-layer tubular sensor collects separate readings from different sections of the soil profile, helping users observe how irrigation water moves downward through the root zone.

For example, a multi-depth sensor can help identify whether:

• Water remains only near the soil surface
• Irrigation has reached the active crop root zone
• Water is moving below the main roots
• A deeper layer remains dry
• Excess irrigation may be causing deep percolation
• Soil temperature differs between shallow and deeper layers

This profile data gives irrigation managers more context than a single moisture reading.

Why Monitor Soil Moisture at Different Depths?

Soil water is not distributed evenly through the profile. Rainfall, irrigation volume, soil texture, drainage, evaporation and crop uptake all influence moisture at each depth.

A shallow sensor may respond quickly after irrigation but cannot confirm whether water has reached deeper roots. A deep sensor may remain wet even when the upper root zone is becoming dry.

Multi-layer monitoring helps users understand three important processes:

Water Infiltration

Comparing readings at different depths shows how quickly water moves downward after irrigation or rainfall.

Root-Zone Water Availability

Measurements can be aligned with the primary and secondary root zones of the crop, helping users evaluate whether available water is located where plants can use it.

Deep Drainage Risk

If the deepest layer becomes wetter soon after every irrigation event, the applied water may be moving below the effective root zone. This can indicate that irrigation duration or volume should be reviewed.

Sensor data should be interpreted together with crop type, growth stage, soil characteristics, weather and irrigation system performance.

How the Tubular Soil Profile Sensor Works？

The JW-TRSQ(LC3) uses high-frequency dielectric sensing technology to detect changes in the surrounding soil.

The measurement signal operates near 1 GHz and penetrates the sealed PVC housing. Because the sensing components do not need exposed electrodes in direct contact with the soil, the structure helps reduce corrosion and direct contamination from fertilizer or irrigation residues.

Each sensing layer measures the surrounding cylindrical soil area. The sensor converts the measurement into digital values and transmits data through RS485 Modbus RTU.

A typical data flow is:

Multi-Layer Soil Sensor → RS485 Data Logger or RTU → 4G, LoRaWAN or Ethernet Gateway → Cloud Platform

The wireless communication method is provided by the connected data logger, RTU or gateway rather than directly by the tubular sensor.

JW-IoT can integrate the sensor into broader smart agriculture IoT solutions involving soil, weather, irrigation and cloud monitoring.

Measured Parameters

Soil Moisture

The sensor measures volumetric soil moisture from 0 to 100% Vol. Separate layer values help users evaluate moisture distribution through the monitored soil profile.

Soil Temperature

Soil temperature is measured at the configured monitoring layers. Temperature information can support crop growth analysis, irrigation interpretation, frost studies and soil research.

Soil Profile Trends

Although the sensor does not physically measure water flow, the time sequence of moisture values at different depths can help users analyze infiltration, retention, water uptake and drainage trends.

Technical Specifications

Actual structure, length and layer positions should be confirmed according to the selected configuration before ordering.

3-Layer, 4-Layer or 5-Layer: How to Select

The number and position of measuring layers should be based on the crop root profile and the purpose of monitoring.

3-Layer Sensor

A 3-layer version may be suitable when the project needs to compare shallow, middle and deeper root-zone moisture with a relatively simple data structure.

Typical uses include:

• Vegetable fields
• Greenhouses
• Shallow-rooted crops
• Basic irrigation evaluation
• Demonstration monitoring stations

4-Layer Sensor

A 4-layer configuration provides additional detail for observing water movement through medium-depth soil profiles.

It may be suitable for:

• Grain crops
• Orchards with developing roots
• Research plots
• Irrigation uniformity studies
• Soil water balance monitoring

5-Layer Sensor

A 5-layer version offers a more detailed vertical moisture profile and may be selected for deeper root systems, long-duration monitoring or research projects.

Typical applications include:

• Mature orchards
• Vineyards
• Deep-rooted crops
• Pasture and grassland
• Drought monitoring
• Hydrology and soil research

These examples are general guidance rather than fixed installation rules. Final layer depths should be selected according to crop species, soil profile, irrigation method and project objectives.

JW-IoT can provide customized sensing positions when the standard layer configuration does not match the required root-zone depths.

Multi-Layer Sensor vs Single-Point Soil Probe

A tubular profile sensor is preferable when the objective is to understand vertical water movement at one representative location.

Separate point sensors may be preferable when the objective is to compare many horizontal locations or when moisture, EC and temperature must all be measured at each individual point.

For projects requiring soil electrical conductivity in addition to moisture and temperature, see the Soil Moisture EC Temperature Probe for Precision Farming.

Output and RS485 Modbus Integration

The sensor uses an RS485 interface with Modbus RTU protocol. It can be connected to:

• Agricultural data loggers
• Remote telemetry units
• PLCs
• Irrigation controllers
• IoT gateways
• Industrial computers
• Local monitoring displays
• Solar-powered field stations

Supported serial communication settings include 8N1 and optional baud rates of 1200, 2400, 4800 and 9600 bps.

Before integration, confirm:

• Sensor power supply
• RS485 A and B wiring
• Communication address
• Baud rate
• Register definitions
• Data type and byte order
• Sampling interval
• Grounding and surge protection requirements

For temporary field commissioning or manual inspection, the sensor may also be connected to a compatible handheld sensor data logger for agriculture field testing.

Smart Irrigation System Architecture

A complete irrigation monitoring system may include:

1. Multi-layer soil moisture and temperature sensor
2. RS485 data logger or RTU
3. Rainfall and weather sensors
4. 4G, LoRaWAN, NB-IoT or Ethernet communication
5. Cloud monitoring platform
6. Irrigation controller
7. Solenoid valves, pumps or control relays
8. Alarm and reporting functions

The soil profile sensor supplies field measurements. The controller or cloud platform applies the configured irrigation logic.

A typical system may use shallow-layer moisture to identify surface drying, middle-layer moisture to assess root-zone water availability and deep-layer moisture to detect possible excess irrigation. The actual control thresholds must be established for the crop, soil and irrigation method at the deployment site.

See the JW-IoT Wireless Smart Irrigation System for related project applications.

Installation Guide

Correct installation is critical because air gaps, stones and loose soil around the tube can reduce measurement representativeness.

1. Select a Representative Location

Choose an area that reflects normal crop, soil and irrigation conditions.

Avoid:

• Field edges
• Drainage channels
• Leaking emitters
• Large stones
• Large roots
• Vehicle tracks
• Depressions with abnormal water accumulation
• Areas directly beside irrigation pipes unless specifically required

2. Confirm the Required Monitoring Depth

Check the sensor length, ground reference mark and sensing layer positions before drilling.

The upper sensing section should align with the intended shallow monitoring depth, while lower layers should correspond to the crop root profile or hydrological observation plan.

3. Drill a Vertical Hole

Use a suitable soil auger to create a straight hole at approximately 90 degrees to the ground surface.

The hole diameter should match the sensor body as closely as practical. An oversized hole may create air gaps or poor contact between the surrounding soil and the sensing tube.

4. Prepare Fine Soil or Soil Slurry

Remove stones, roots and coarse debris from the excavated soil.

When required by the installation method, mix fine native soil with water to form a uniform slurry. Using soil from the same location helps maintain representative contact around the sensor.

5. Partially Fill the Hole

Place the prepared soil or slurry into the hole according to the installation instructions. Do not leave large air pockets.

6. Insert the Sensor Vertically

Lower the tubular sensor slowly into the hole. Slight rotation may help release trapped air and distribute the surrounding soil material.

Do not use excessive force, strike the housing or push the probe against stones.

7. Align the Ground Reference Mark

Make sure the designated ground line is level with the soil surface. Incorrect vertical position will shift all measurement layers away from their intended depths.

8. Compact and Stabilize the Surrounding Soil

Remove excess slurry and gently compact the surface soil around the probe.

Allow the installation area to stabilize before treating the initial readings as the long-term baseline.

9. Record Installation Information

Document:

• Sensor model and serial number
• GPS or site location
• Installation date
• Crop and growth stage
• Soil type
• Layer depths
• Irrigation method
• Cable route
• Communication address
• Initial readings

These records are important when comparing data across fields and monitoring seasons.

Application Scenarios

Water-Saving Irrigation

Multi-depth moisture data helps users determine whether irrigation water remains near the surface, reaches the active root zone or passes into deeper soil.

It can support drip, sprinkler and other controlled irrigation projects.

Open-Field Crop Monitoring

The sensor can be deployed in corn, wheat, vegetables, cotton and other field crops to monitor water infiltration and root-zone conditions.

Multiple sensors may be installed in different management zones when soil texture, elevation or irrigation uniformity varies across the field.

Orchard and Vineyard Irrigation

Orchards and vineyards may contain both shallow feeder roots and deeper structural roots. A multi-layer profile helps evaluate moisture availability across these zones.

Sensor positions should represent the wetting pattern created by drippers or micro-sprinklers.

Greenhouse Cultivation

In greenhouse vegetable, flower and seedling production, the sensor supports root-zone moisture and temperature monitoring for irrigation scheduling.

For smaller containers or substrate applications where EC measurement is also required, consider the Soil Moisture EC Temperature Probe for Substrate and Soil Testing.

Precision Agriculture

The sensor can be connected to an RTU or IoT gateway to create a digital soil monitoring network.

Data from multiple field zones can be combined with rainfall, weather, crop and irrigation records to support management decisions.

Pasture and Grassland

Long-term profile measurements can support pasture irrigation, ecological research, vegetation monitoring and drought assessment.

Soil and Irrigation Research

Agricultural universities and research institutes can use multi-layer data to study:

• Soil water movement
• Infiltration rates
• Moisture retention
• Irrigation treatments
• Crop water uptake
• Soil temperature profiles
• Drought response
• Water balance

Water Conservancy and Hydrology

The sensor may be used in watershed observation, drought monitoring, soil water balance studies and water conservancy projects where profile moisture information is required.

Soil Contact and Measurement Area

The sensor measures a cylindrical soil area around the probe rather than only the surface of the tube.

For the current model, the approximate moisture measurement area extends across a cylindrical zone of about 10 cm in diameter around the sensor.

Because the surrounding soil contributes to the reading, installation quality is important. Large air spaces, stones or non-representative backfill can cause the measured zone to differ from the undisturbed field soil.

After installation, readings may also change while the soil settles and moisture redistributes around the probe.

Fertilizer and Soil Salinity Considerations

The sealed PVC tube and high-frequency detection method help reduce direct problems associated with exposed metal electrodes, including corrosion and deposits.

However, soil texture, bulk density, temperature, salinity and installation conditions may still influence dielectric soil moisture measurements to varying degrees.

For projects requiring high comparability across unusual soil types or strongly saline conditions, site verification or soil-specific calibration should be considered.

When direct EC and salinity monitoring is required, a dedicated soil moisture and EC sensor should be used rather than inferring salinity from moisture data alone.

Data Interpretation for Irrigation

A single moisture value should not automatically trigger irrigation without considering the complete field context.

Useful interpretation may include:

• Comparing each layer with its own baseline
• Watching the sequence in which layers respond after irrigation
• Evaluating drying rates between irrigation events
• Comparing profile data with rainfall
• Reviewing deep-layer increases for drainage risk
• Adjusting thresholds by crop growth stage
• Comparing several representative monitoring zones

Irrigation thresholds should be established using crop requirements, soil characteristics and local agronomic experience.

The sensor provides measurement data; it does not independently determine the correct irrigation volume for every crop and field.

Operation and Maintenance

Recommended inspection tasks include:

• Check the exposed cable and connector
• Protect cables from machinery and animals
• Inspect the data logger power supply
• Confirm RS485 communication
• Review values for abrupt or unrealistic changes
• Compare readings with rainfall and irrigation records
• Check whether field construction has disturbed the sensor
• Back up historical data
• Record maintenance and system changes

Because the tubular probe is installed below ground, it should not be repeatedly removed unless maintenance or relocation is necessary.

Related Soil Monitoring Options

This multi-layer sensor is designed primarily for vertical soil profile monitoring.

Other JW-IoT products may be more appropriate for different measurement objectives:

• Use a Soil Moisture EC Temperature Probe for Precision Farming when local moisture, temperature and EC must be measured together.
• Use a Soil Moisture EC Temperature Probe for Substrate and Soil Testing for local soil or growing-media measurements.
• Use a Soil NPK Moisture Sensor for Farming when the project requires additional soil nutrient indicators.
• Use a Handheld Sensor Data Logger for field inspection, commissioning and portable sensor readings.
• Browse the complete Soil Sensors category for other monitoring options.

Request a Multi-Layer Soil Monitoring Solution

Please provide the following information when requesting a quotation:

• Crop type
• Approximate root depth
• Required number of layers
• Preferred measurement depths
• Soil type
• Irrigation method
• Number of monitoring locations
• RS485 cable length
• Data logger or RTU requirement
• 4G, LoRaWAN or other communication requirement
• Cloud platform or API requirement
• Installation country and project schedule

Contact JW-IoT to configure a multi-layer soil moisture and temperature monitoring solution for your irrigation, agriculture or research project.