Soil Moisture Sensors Give Farmers Better Irrigation Data

Knowing when to irrigate is still a hands-on decision for many farmers. A field may have been watered recently, but that does not mean every part of it has the same amount of moisture. Soil type, drainage, weather and the crop itself all play a part.

A simple walk across the field cannot show everything happening below the surface. This is why soil moisture sensors are being used to take readings from the soil itself. The sensors can be installed at different depths and used to record moisture levels over a period of time.

The information can be particularly useful between rainfall and irrigation. Instead of checking the soil only when a decision has to be made, growers can look at a series of readings and see how quickly moisture is being lost.

Oklahoma State University published guidance on the subject in 2026. It discusses the use of trend values from soil moisture sensors for irrigation decisions, rather than relying on an isolated reading. Oklahoma State University guidance on soil moisture sensors

Knowing What Is Happening Beneath the Crop

A sensor buried in the wrong place will not tell a farmer much. The depth of the crop's roots is one consideration. The soil around the sensor is another.

University of Minnesota Extension recommends taking the crop root zone, soil conditions and irrigation method into account when installing sensors. More than one sensor depth may be useful when the aim is to see how moisture changes through the soil profile. University of Minnesota Extension guidance on soil moisture sensors

There is also a difference between getting a reading and getting a reliable reading.

Researchers with the USDA Agricultural Research Service tested five commonly used moisture sensors in 2026. Their study found that factory calibration did not account for all variations in soil texture and composition. USDA Agricultural Research Service sensor calibration study

That matters because soil is rarely identical from one farm to another. A sensor placed in a sandy soil is dealing with different conditions from one placed in a heavier soil. The way water moves through those soils is different too.

For anyone using sensor data, the surroundings of the device matter just as much as the number appearing on the screen. Placement, calibration and the depth of the sensor all affect the result.

From Irrigation Readings to Field-Level Data

Moisture is also being measured with other field conditions. The USDA Agricultural Research Service has a project in Missouri that brings together soil electrical conductivity, in-ground moisture sensing, field-scale mapping, digitally controlled irrigation and remote sensing. USDA Agricultural Research Service digital agriculture project

There is a reason for looking at several measurements. A field can change considerably from one section to the next. Water may move quickly through one area and stay longer in another. A map can show those differences in a way that a single measurement cannot.

Different soil sensors are available for different jobs. Some measure moisture. Others can provide readings for temperature or electrical conductivity. In larger systems, readings from several locations can be collected and compared.

The technology does not remove the practical work involved in farming. Sensors have to be installed, checked and maintained. A reading also has to be considered alongside rainfall, crop growth and other conditions before an irrigation decision is made.

For researchers, having all of this information in one place is useful. They can compare soil readings with irrigation activity and field conditions and see how they change during the growing season.

The Next Step Is Measuring the Plant

The soil is not the only source of information being studied. A 2026 report from the USDA National Institute of Food and Agriculture describes research involving the University of Georgia, Iowa State University and the University of Nebraska-Lincoln. Researchers are working with small sensors that can be attached to plants. The devices are being used to study temperature, humidity and bioelectric activity, as well as signals related to water and nutrients. USDA NIFA research on plant-mounted sensors

That gives researchers another way to look at water stress. A sensor in the ground records what is happening around the roots. A sensor on the plant records a response from the crop itself.

The research fits into the wider area of soil health monitoring, where moisture is considered alongside other soil characteristics. Soil properties can change over time, and measurements from sensors and remote sensing can help researchers follow those changes.

USDA projects are also looking at ways to connect soil measurements, remote sensing and precision irrigation. USDA Agricultural Research Service precision irrigation research

For farmers, the immediate use of these systems remains irrigation. A moisture reading can show what is happening below the surface when the field itself gives few clues. Across a large farm, readings from several locations can also show where conditions differ.

The research now underway goes further than that. Scientists are collecting information from soil, plants and the surrounding field at the same time. Some of the work is already being tested in agricultural settings, while other systems are still under development.

The basic question has not changed: does the crop have enough water? What has changed is the amount of information available for answering it.

FAQs

1. What are soil moisture sensors used for?
They measure moisture in the soil at selected depths. The readings can be followed over time and used as part of irrigation planning.

2. Does the position of a sensor matter?
Yes. The crop's root depth, soil conditions and irrigation method all affect where a sensor should be placed.

3. What can soil sensors measure?
Depending on the device, they can measure moisture, temperature, electrical conductivity and other soil conditions.

4. What does soil health monitoring involve?
It involves collecting information about soil conditions and following changes over time. Moisture is one of several factors that can be measured.

5. Are researchers putting sensors on plants?
Yes. Research teams are testing small sensors attached to plants to measure factors such as temperature, humidity and bioelectric activity.

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