Can Soil Sensors Tell Farmers When to Irrigate? What Should Small Farmers Know Before Buying Them?

Farmers often decide when to irrigate by looking at the soil surface or following a fixed schedule. Soil-moisture sensors offer another approach by measuring moisture inside the root zone. ICAR-CRIJAF recently trained farmers in West Bengal on sensor-based water management for jute-based cropping systems.

The technology can help farmers base irrigation decisions on measured soil conditions rather than applying water simply because a particular number of days has passed. But a sensor is only useful when installed correctly and interpreted according to the crop, soil type and irrigation method.

A soil-moisture sensor measures the amount of water present in soil around the sensor. Different technologies estimate moisture in different ways, and the reading can be expressed in different units depending on the equipment.

The useful question for farmers is not simply whether soil is wet. They need to know whether enough moisture remains available around the crop’s active roots to support healthy growth without unnecessary irrigation.

A sensor is placed at an appropriate depth in the crop’s root zone. It records changes in soil moisture as plants use water or rainfall adds moisture to the field. Farmers can use the readings to decide when irrigation is needed. More advanced systems can connect sensors with controllers, pumps and valves so irrigation can be automated when defined moisture conditions are reached.

Why is sensor depth important?

A sensor placed too close to the surface may dry quickly and give a misleading picture of moisture available to deeper roots. A sensor placed too deep may miss conditions affecting shallow-rooted crops. The correct depth depends on crop rooting depth, soil type and irrigation method. Farmers should follow crop-specific technical guidance rather than placing sensors at an arbitrary depth.

They can help avoid irrigation when soil already contains sufficient moisture. This can reduce unnecessary watering, particularly where farmers normally irrigate according to a fixed calendar. The amount of water saved will vary with crop, soil, rainfall, irrigation system and farmer practices. A sensor does not automatically reduce consumption unless farmers use its readings to change irrigation decisions.

ICAR-CRIJAF organised a farmer training programme on sensor-based water management in jute-based cropping systems in West Bengal. The programme involved 80 farmers and focused on using technology for more informed irrigation decisions.  The training included practical exposure to sensor-based irrigation and water management. Such demonstrations matter because farmers need to understand not only what a sensor measures but also how those readings translate into field decisions.

Yes, but the economics need checking. A farmer with a small plot may not benefit from expensive equipment if the potential water savings are too low to recover the investment. Farmers can consider shared equipment, demonstrations or custom services where available. Before purchasing, they should compare equipment cost with irrigation expenses and the expected reduction in unnecessary watering.

Does one sensor cover an entire farm?

Not always. Soil conditions can vary within the same field, especially where there are differences in texture, slope, crop growth or irrigation distribution. A sensor provides information from the location where it is installed. Farmers with larger or variable fields may need more than one measurement point to understand moisture conditions across the crop.

Soil-moisture monitoring can be used across many irrigated crops, including vegetables, fruits, cereals and fibre crops. The usefulness depends on crop rooting depth, irrigation method and how frequently water availability changes. The sensor threshold also needs to be interpreted differently for different crops and soils. A reading that indicates adequate moisture for one crop may not be suitable for another.

Yes. Soil-moisture sensors can complement drip irrigation by helping determine when irrigation is required. Drip systems deliver water directly near the crop root zone, while sensors provide information about moisture conditions. Together, they can help farmers avoid applying water simply according to a fixed timer. The system still needs correct installation, filtration and maintenance to operate properly.

What is the difference between a sensor and automation?

A sensor measures soil conditions. Automation adds equipment that can use those measurements to control irrigation without requiring the farmer to switch the system manually. A basic sensor setup may only display moisture readings. An automated system can connect sensors to controllers, pumps and valves, making it more expensive and requiring additional technical maintenance.

The answer depends on the equipment. Some systems use batteries, while more advanced installations may require a continuous power source or solar supply. Farmers should ask about battery life, replacement cost and power requirements before purchasing. A sensor that stops recording because its power source fails can provide little value during a critical irrigation period.

Some modern systems send readings to a mobile phone or online dashboard. Others simply display measurements locally. Farmers should not pay for connectivity features they do not need. If mobile coverage is weak, a system requiring constant internet access may be less practical than equipment that provides readings directly in the field.

Sensors need proper installation and regular checking. Soil movement, physical damage, poor connections and incorrect placement can affect readings. Farmers should follow the manufacturer’s instructions for cleaning, calibration and storage. They should also compare sensor readings with actual field conditions instead of assuming every reading is automatically correct.

Can farmers irrigate only by sensor readings?

Not necessarily. Sensor readings should be considered alongside weather forecasts, rainfall, crop growth stage and irrigation system performance. A field may receive rainfall shortly after an irrigation decision is made. Farmers can combine sensor information with weather conditions to avoid unnecessary watering while ensuring crops receive adequate moisture during critical growth stages.

Farmers should check the sensor’s measurement range, required depth, accuracy, power source, durability, calibration requirements and compatibility with their soil and irrigation system. They should also ask whether local technical support is available. A cheaper sensor that cannot be installed or interpreted correctly may provide less value than a system supported by trained technicians.

Is the technology worth the cost?

That depends on the farm. Farmers with high irrigation costs, limited water supplies or crops sensitive to water stress may have more reason to consider sensor-based management. The calculation should include equipment, installation, maintenance and replacement costs. Farmers should compare these expenses with possible water savings, improved crop management and labour saved through better irrigation scheduling.

Soil-moisture sensors do not replace the farmer’s judgement. They provide another source of information about what is happening below the soil surface, where crop roots obtain water. For small farmers, the decision should begin with a simple calculation. How much do you spend on irrigation, how often do you water, and could reliable moisture information change those decisions enough to justify the equipment cost?