Can Soil-Moisture Sensors Tell Farmers When to Irrigate?

A farmer often decides when to irrigate by looking at the crop, touching the soil or following a fixed schedule. These methods come from experience, but they do not always show how much water is actually available around the roots.

Soil-moisture sensors offer another way to make that decision. They measure moisture in the soil and provide information that can help farmers decide when irrigation is needed.

In September 2026, ICAR-CRIJAF and CSIR-CMERI trained 80 farmers in West Bengal on sensor-based water management and demonstrated IoT-based irrigation systems under field conditions. The aim was to move away from fixed irrigation schedules towards irrigation based on actual field conditions.

What does a soil-moisture sensor do?

A soil-moisture sensor measures the amount of water present in the soil. Different sensors use different methods to measure this moisture.

Capacitance sensors detect changes in the soil’s electrical properties. Time Domain Reflectometry sensors use electromagnetic signals, while tensiometers measure the force with which plant roots need to extract water from the soil.

The information can tell farmers whether the soil is relatively dry or has enough moisture for the crop.

This matters because the surface of the soil does not always tell the whole story. The top layer may look dry while moisture remains deeper in the root zone, or the surface may appear wet after rain even though another part of the field needs attention.

How can the sensor change irrigation?

Traditional irrigation often follows a calendar. A farmer may irrigate every few days because that has worked in the past.

A sensor-based system works differently. It provides information about current soil conditions. The farmer can then decide whether irrigation is required.

If the soil still contains enough moisture, irrigation can potentially be delayed. If moisture falls below the level required by the crop, the farmer can irrigate.

ICAR says sensor-based irrigation can help farmers apply water only when and where it is required. Its technology database lists an IoT-enabled soil-moisture sensing system for irrigation scheduling that has shown 10–15% water savings compared with traditional scheduling in the reported application.

The actual saving on a farm will depend on the crop, soil, irrigation method, weather and how the system is used.

Sensors can also work with irrigation systems

A sensor does not have to be used only as a device that displays information.

It can also become part of an automated irrigation system. Sensors can send soil-moisture readings to a controller, which can then operate valves or pumps according to predefined conditions.

IoT-based systems can combine sensor readings with weather information and crop requirements. Some systems can send information to a mobile application so farmers can check field conditions remotely.

This can be useful for farmers who manage several fields or cannot physically inspect every plot several times a day.

But automation should be based on appropriate thresholds and crop needs. A machine should not simply switch irrigation on whenever the soil becomes slightly dry.

What is happening in Indian farms?

ICAR-RCER in Patna established an indigenous IoT-enabled soil monitoring system in May 2026. The project was developed with Birla Institute of Technology Mesra to address problems including erratic rainfall, declining groundwater levels, rising irrigation energy costs and inefficient water application.

The system is being tested under field conditions, with calibration and performance evaluation still underway. ICAR-RCER says the aim is to develop affordable and farmer-friendly technology suitable for wider use.

In West Bengal, ICAR-CRIJAF and CSIR-CMERI demonstrated another sensor-based approach in jute-based cropping systems in September 2026. Farmers received hands-on exposure to IoT irrigation prototypes that had been deployed and operated under field conditions.

These examples show that the technology is moving beyond laboratory research and into field testing and farmer training.

Can small farmers use the technology?

Cost is one of the biggest questions.

A sensor may be affordable on its own, but a complete smart irrigation system can also require controllers, connectivity, power supply, valves and irrigation equipment.

For a small farmer, buying an expensive system for a small plot may not make economic sense. Shared systems could be more practical where several farmers use the same equipment or where an FPO, cooperative or farmer group manages the technology.

ICAR has specifically highlighted the need for affordable, scalable and farmer-friendly soil-monitoring technology in its Patna project.

Farmers should therefore calculate the full cost before purchasing. The question is not simply how much the sensor costs, but how much water, electricity, labour or crop loss the system could potentially save.

What should farmers check before buying?

Farmers should first check whether the sensor is suitable for their soil, crop and irrigation method.

Sensor placement is also important. One sensor may not represent an entire field if soil conditions vary significantly from one area to another.

Farmers should ask how deep the sensor measures moisture, how often it needs calibration, how the readings are displayed and whether technical support is available locally.

They should also check whether the system continues to work during power or internet interruptions. A farmer should not depend entirely on a digital reading without understanding the field itself.

The best use may be to combine sensor readings with crop observation, weather forecasts and local agricultural advice.

The goal is not to irrigate less. It is to irrigate better.

Saving water does not mean giving crops less water than they need. The aim is to supply the right amount at the right time.

ICAR describes water-smart irrigation as using tools and data to match water application with crop needs and environmental conditions. Such systems can reduce unnecessary irrigation, runoff and water losses while improving water-use efficiency.

This becomes more important where groundwater levels are falling or pumping water is becoming expensive.

For farmers, the biggest change is simple: irrigation can move from a fixed routine towards a decision based on what is actually happening in the soil.

The farmer will still decide when to irrigate. But instead of relying only on the calendar or appearance of the field, there can be another piece of information beneath the surface.

A small sensor in the soil could tell the farmer something the eye cannot always see: whether the crop’s root zone actually needs water.