Sensors for irrigation systems

Sensors for irrigation systems measure soil, water and weather conditions that affect irrigation decisions. Common irrigation sensors include soil moisture sensors, soil temperature sensors, flow meters, pressure sensors, water level sensors, rainfall sensors and environmental monitoring instruments.

In modern agriculture, these sensors provide measurement data that can help farmers and irrigation system integrators evaluate soil water conditions, monitor water delivery and identify potential operating problems. The measurements can be collected by compatible PLCs, irrigation controllers, RTUs, data loggers and IoT gateways.

A sensor measures a physical parameter; it does not necessarily control irrigation equipment. Automatic watering requires a suitable controller, control logic, power supply and actuators such as solenoid valves or pump-control equipment.

What Sensors Are Used in Irrigation Systems?

The required sensors depend on the irrigation method, crop, soil characteristics, water supply and monitoring objectives. A drip irrigation system may prioritize soil moisture and water flow, while a large agricultural irrigation project may also need reservoir water level, pipeline pressure, rainfall and weather measurements.

1. Soil Moisture Sensors for Irrigation

A soil moisture sensor measures the amount of water present in the soil around its sensing element. Many agricultural sensors estimate volumetric water content (VWC), commonly expressed as a percentage.

Soil moisture sensors are important for irrigation monitoring because they provide direct information about water conditions in the monitored root zone. Measurements can be compared with irrigation thresholds or used together with rainfall, crop and weather data.

A sensor installed in one soil location does not necessarily represent an entire field. Soil texture, rooting depth, irrigation distribution and installation position should be considered when determining the number of monitoring points.

How Soil Moisture Data Is Used

In a moisture-based irrigation system, the controller reads soil moisture data and compares it with a defined control strategy. For example, irrigation may be permitted when the soil is sufficiently dry or postponed when moisture is already above the selected threshold.

The controller, rather than the soil moisture sensor itself, operates the associated valves or pump equipment.

Soil Moisture Sensor

4-in-1 Soil Sensor

Soil pH Sensor

2. Soil Temperature Sensors

A soil temperature sensor measures temperature at the installed soil depth. Soil temperature affects root activity, biological processes and plant growing conditions.

Soil temperature data provides useful context for interpreting root-zone conditions and seasonal changes. It may be combined with soil moisture data when planning irrigation or evaluating crop growing environments.

Soil temperature does not independently determine how much irrigation water is required. It should be considered together with soil moisture, crop requirements and other environmental measurements.

3. Water Flow Sensors and Irrigation Flow Meters

A water flow sensor measures the rate of water movement through a pipe or open channel. A flow meter may also provide a cumulative water volume measurement.

In irrigation systems, flow measurement is useful for verifying water delivery, monitoring water consumption and identifying abnormal operating conditions.

Flow Rate vs Total Water Volume

Flow rate describes how much water passes through a measurement point per unit time, commonly expressed in m³/h or L/min. Total volume represents the accumulated amount of water delivered over a period, commonly expressed in m³ or liters.

A controller can use flow measurements together with pump and valve status to identify possible leaks, blockages or unexpected water delivery. However, a flow sensor alone does not determine the cause of an abnormal reading.

Pipe flow sensors and open-channel flow instruments use different measurement technologies. Select the instrument according to whether the irrigation system uses a pressurized pipeline, open canal or another water delivery arrangement.

4. Water Pressure Sensors

A water pressure sensor measures the pressure of water within an irrigation pipeline or hydraulic system.

Pressure measurements help operators monitor pump discharge conditions, filter pressure changes and the hydraulic performance of irrigation zones.

For example, pressure readings collected before and after a filter can be used by a suitable monitoring system to calculate pressure difference. An increasing differential pressure may indicate a developing filter restriction.

Pressure sensors can also provide input to pump-control systems, but automatic pump regulation requires a compatible controller and appropriate electrical equipment.

The measurement range, pressure connection, wetted materials and output signal should be selected according to the actual irrigation installation.

5. Water Level Sensors for Irrigation Water Supply

A water level sensor measures liquid level in a reservoir, storage tank, groundwater well or other irrigation water source.

Water level measurements are useful for evaluating available water and providing information to properly designed pump-protection or water management systems.

Common continuous level measurement technologies include non-contact radar and submersible hydrostatic pressure transmitters. The appropriate sensor depends on installation access, measurement range, water conditions and whether direct contact with water is acceptable.

A level sensor measures the water level. Low-water pump protection or automatic refill control requires a compatible controller, suitable thresholds and correctly configured actuators.

6. pH and Electrical Conductivity Sensors for Irrigation Water

Irrigation water quality can affect crop growing conditions, nutrient management and the performance of fertigation systems. Two commonly monitored parameters are pH and electrical conductivity.

Water pH: Measures the acidity or alkalinity of irrigation water or nutrient solutions. The appropriate measurement range, electrode design and installation depend on the medium and process.

Water EC: Measures electrical conductivity, which is influenced by dissolved ionic substances. EC is commonly used in nutrient solution and irrigation water monitoring but does not independently identify individual nutrient concentrations.

For water-based measurement, use compatible water quality sensors. A soil pH electrode should not automatically be treated as interchangeable with a continuously immersed process-water pH sensor.

The following original image illustrates a soil pH measurement instrument, which is a separate measurement application from irrigation water pH monitoring.

7. Rainfall Sensors for Irrigation Planning

A rainfall sensor or rain gauge provides precipitation information that can be considered when planning irrigation.

Automatic rain gauges commonly measure accumulated rainfall in millimeters. Suitable instruments may also provide rainfall intensity calculated over a defined period.

A tipping bucket rain gauge measures rainfall through calibrated bucket movements. Rainfall records can help determine whether a scheduled irrigation event should be reviewed after natural precipitation.

Rainfall measurement alone does not determine how much water has reached the crop root zone. Surface runoff, infiltration, soil moisture conditions and irrigation method also affect the resulting soil water availability.

Tipping Bucket Rain Gauge

Automatic Rain Gauge

Evaporation Sensor

8. Wind Speed and Direction Sensors

Wind measurements can be important when irrigation water is applied through sprinklers or other methods affected by air movement.

High wind speeds can increase spray drift and affect the uniformity of water distribution. A wind speed sensor provides information that an irrigation operator or suitable controller can use when evaluating operating conditions.

A cup anemometer measures wind speed, while a wind vane measures direction. Some ultrasonic wind sensors provide both measurements in one instrument.

Wind Speed Sensor

Wind Direction Sensor

Temperature, Humidity & Pressure Sensor

9. Air Temperature and Humidity Sensors

Air temperature and relative humidity sensors measure atmospheric conditions relevant to crop water demand and growing environments.

Temperature and humidity influence atmospheric evaporative demand. They are commonly used together with solar radiation and wind measurements in meteorological calculations and irrigation planning.

A combined air temperature and humidity sensor provides useful environmental information, but it does not independently calculate the exact irrigation requirement of a particular crop.

For a complete agricultural weather monitoring configuration, see the Automatic Weather Station selection page.

10. Evaporation and Evapotranspiration Measurements

Evaporation and evapotranspiration are related but different processes. Their distinction is important when using meteorological measurements for irrigation planning.

Evaporation describes the conversion of liquid water into water vapor from surfaces such as open water or wet soil.

Evapotranspiration (ET) includes both evaporation and water vapor loss through plant transpiration.

An evaporation pan or water-level-based evaporation instrument measures changes in the water level of an exposed water surface. That measurement should not automatically be treated as the actual evapotranspiration of an agricultural crop.

Reference evapotranspiration (ETo) can be estimated from suitable meteorological data using recognized calculation methods, such as the FAO Penman–Monteith approach. This method requires appropriate weather inputs and defined calculation conditions.

Crop evapotranspiration estimates additionally depend on crop characteristics and growth stage. Irrigation scheduling should consider these estimates together with effective rainfall, soil moisture and the irrigation system's operating conditions.

How Irrigation Sensors Connect to Controllers and Pumps

A complete irrigation monitoring and control system contains both measurement equipment and control equipment. These functions should be considered separately during system design.

Soil / Water / Weather Sensors → RS485 / Analog / Pulse → Irrigation Controller / PLC → Relay or Valve Driver → Solenoid Valve / Pump

The sensors provide measurements. A controller evaluates the data and issues commands based on a defined irrigation strategy.

Depending on the system, the controller may operate 24 VAC irrigation valves, another compatible actuator voltage or a pump-control interface. The electrical design must match the selected valves, pumps and controller outputs.

Remote monitoring can be added through a compatible data logger or IoT gateway. However, RS485 Modbus sensors should not be assumed to include their own 4G modem or cloud connection.

How Sensor Data Supports Irrigation Decisions

Sensor data can support different irrigation management approaches. The appropriate strategy depends on the crop, soil, irrigation method and controller capabilities.

Soil-Moisture-Based Irrigation

An irrigation controller can compare measured soil moisture with configured thresholds. The controller may permit irrigation when soil moisture is low or prevent a scheduled cycle when sufficient water is already present.

The thresholds should be selected according to soil conditions, crop rooting depth and the intended irrigation strategy. There is no single moisture percentage suitable for every crop and soil type.

Weather-Based Irrigation Planning

Weather-based irrigation planning uses measurements such as rainfall, temperature, humidity, wind and solar radiation to assess environmental conditions and estimate water demand.

These measurements can be used together with crop information and soil conditions. A weather station alone does not independently determine a universal irrigation amount for every planting area.

Flow and Pressure Monitoring

Flow and pressure measurements provide information about the hydraulic operation of an irrigation system.

When combined with valve and pump status, these measurements can help a controller or monitoring platform identify possible water delivery problems, such as leaks, insufficient flow, filter restrictions or abnormal pressure.

Accurate diagnosis requires suitable measurement locations and operating logic. An abnormal flow reading does not automatically identify a specific equipment failure.

Selecting Sensors for Different Irrigation Applications

Different irrigation systems require different sensor arrangements. The following configurations are typical starting points rather than fixed requirements.

The number of monitoring points should reflect irrigation zones, field variability, crop rooting patterns and hydraulic system design.

Benefits and Limitations of Irrigation Sensor Monitoring

Irrigation sensors provide measurements that can improve visibility into soil and water conditions. When integrated with suitable controllers and monitoring methods, they can support better-informed irrigation decisions.

Water-use monitoring: Soil moisture and flow measurements provide information about crop-zone conditions and water delivery. The actual water savings depend on the irrigation strategy and baseline operating conditions.

Hydraulic monitoring: Flow, pressure and water level measurements can support assessment of pumps, filters, pipelines and available water supplies.

Environmental context: Rainfall, temperature, humidity, wind and solar radiation provide information relevant to crop water demand and irrigation planning.

Automation support: Sensor measurements can be used by compatible irrigation controllers to implement schedules, thresholds, fault alarms and equipment-control strategies.

The presence of sensors alone does not guarantee a specific percentage of water savings, higher crop yields or reduced plant disease. These outcomes depend on the complete system design, installation, irrigation management and growing conditions.

Frequently Asked Questions

Which sensors are most important for an irrigation system?

Soil moisture, water flow and pressure sensors are common starting points. Water level, rainfall, weather and water-quality measurements may also be required depending on the irrigation application.

Can a soil moisture sensor automatically operate irrigation valves?

A standard measurement sensor normally provides data rather than directly operating valves. Automatic operation requires a compatible irrigation controller and appropriate electrical output equipment.

Is a flow sensor necessary for every irrigation project?

Not necessarily. However, flow measurement is useful when the project needs to verify water delivery, track consumption or identify abnormal hydraulic conditions.

Can RS485 irrigation sensors connect to a PLC?

Yes. Sensors with compatible RS485 Modbus RTU outputs can connect to PLCs, RTUs and data loggers that support the required electrical and communication settings.

Can irrigation sensor data be monitored remotely?

Yes. A compatible data logger or IoT gateway can collect sensor measurements and transmit them to a monitoring platform or private server through a supported communication network.

Irrigation Monitoring Sensors from NiuBoL

NiuBoL provides soil, weather, water level and water-quality sensors for agricultural monitoring and integration with compatible irrigation control and data acquisition systems.

Available measurement options include soil monitoring sensors, weather station sensors, water level sensors and water-quality monitoring sensors.

For sensor selection and quotation, specify the irrigation method, crop, soil conditions, number of irrigation zones, required measurements, output interfaces, power supply, cable length, monitoring system and project quantity.