When sensor readings need context: turning PEATLESS data into irrigation decisions

CESENS is analysing continuous monitoring data to correct misleading patterns, understand changes in substrate salinity and develop practical irrigation alerts.

A sensor reading is not automatically a useful result. Before monitoring data can support irrigation management, researchers must determine whether each variation reflects a real change in the growing medium or an external effect influencing the equipment.

The first continuous datasets analysed by CESENS have already revealed both situations. Some patterns initially appeared to show changes in substrate moisture but were caused by temperature. Other variations provided useful information about salinity, irrigation and crop management events.

These findings illustrate an important part of the PEATLESS approach to testing alternative growing media: measurements must be interpreted in relation to the properties of each formulation and the conditions surrounding the trial.

A daily cycle caused by heat, not water

The outdoor moisture readings showed a repeated daily pattern. Values increased and decreased at similar times each day, apparently indicating changes in the water content of the substrate.

Further analysis demonstrated that the cycle had nothing to do with water.

The sensor head and cable were exposed to direct sunlight and became considerably warmer than the growing medium. This temperature difference affected the measurements and generated an artificial variation in the moisture data.

CESENS quantified the effect and applied an individual correction to the affected sensors. The adjusted data removed the false daily cycle while preserving genuine irrigation events and the longer-term trend.

Not every variation in a sensor reading represents a change in the growing medium. Context is essential for interpreting continuous data correctly.

Identifying and correcting this effect prevents temperature-related interference from being mistaken for water loss or an irrigation response.

Salinity as a process rather than a snapshot

Continuous monitoring also provided a more detailed view of how salinity changed over time.

The compost-based formulations began with considerably higher salinity levels than the peat control. The data showed how these salts were progressively washed out by irrigation during the first weeks of the trial.

As irrigation continued, the values recorded in the compost-based growing media gradually moved closer to those of the peat control.

A single measurement could show the salinity level at one particular moment. Continuous data revealed the complete process, including the changes occurring between individual irrigation events.

The system also registered an unexpected increase in salinity that did not follow the previous pattern. Further investigation showed that it coincided with a crop treatment applied to the beds.

Continuous monitoring can reveal gradual trends and unexpected events that may remain hidden between occasional measurements.

The data do not automatically explain why an unusual event has occurred, but they help researchers identify when to investigate its cause.

From raw measurements to available water

Raw sensor values have limited practical meaning for growers. Knowing that a sensor has recorded a particular value does not necessarily indicate how much water remains available to the crop or whether irrigation is needed.

CESENS is therefore translating the measurements into an index of readily available water.

The calculation is anchored to the physical characterisation of each growing medium. This is important because the same raw value may have different implications depending on the properties of the formulation being monitored.

The weighing-based approach follows the same principle. Instead of presenting weight changes alone, the system can trigger an alert once the monitored unit has lost a defined proportion of its available water.

This turns the measurement into a clearer operational message: the growing medium is approaching the point at which irrigation may be required.

Configurable alerts for new formulations

The interpretation settings and alert thresholds can be configured without programming. As new formulations enter the trials, the monitoring system can therefore be adjusted to reflect their individual physical characteristics.

This adaptability is necessary because alternative growing media do not all retain and release water in the same way. A single threshold would not provide an equally meaningful indication for every formulation.

The next step is to validate this approach in additional facilities. The systems will be extended to INAGRO in Belgium and ZHAW in Switzerland, allowing the interpretation methods and alerts to be assessed under new conditions.

This work complements the validation of reduced-peat and peat-free formulations at INAGRO and will help determine whether the monitoring tools can provide consistent, practical information across different growing media and facilities.

For growers considering alternative substrates, the objective is not simply to collect more data. It is to obtain information that helps them understand how those materials behave and when irrigation may be necessary.