Spiio™ soil sensors continuously monitor moisture, temperature, and salinity at rootzone depth. This article explains what our internal trial data shows about how installation affects your readings, why Spiio numbers may differ from a TDR meter, and how rainfall relates to what your sensors report.
Data sourced from internal Spiio installation trial (Protocol Spiio123, April 2026). Research conducted by Morgan Bragg and Ilse Barrios, Syngenta Data Science team.
Does Installation Method Affect My Sensor Data?
No, your readings are reliable regardless of how the sensor was physically installed.
In a controlled field trial, Spiio sensors were installed using multiple installation methods and monitored over an extended period. Soil moisture, soil temperature, and soil salinity were all analyzed to determine whether the method of installation changed the data.
Key finding across all three measurements:
Installation method had no statistically significant effect on moisture, temperature, or salinity readings.
The factor that drove differences in readings was time of year, month and season, not how the sensor was put in the ground.
What this means for you: if you've installed sensors across your property using slightly different methods; hand-pressed, machine-assisted, or otherwise, your data is still valid and comparable. Seasonal variation in your rootzone is real, expected, and exactly what the sensor is designed to track.
Why Do My Spiio Readings Look Different from My TDR?
Spiio sensors and TDR meters measure soil moisture differently, this is expected, not a sign something is wrong.
In the same trial, Spiio sensor data was compared directly against TDR 350 handheld meter readings taken at matched timepoints. The results showed a consistent pattern:
Spiio sensors reported an average moisture reading approximately 11% higher than the TDR 350.
Spiio readings showed less variability over time (smaller standard deviation), while TDR readings showed more variability from measurement to measurement.
This difference was consistent across installation methods, it wasn't caused by how the sensor was installed.
Why the difference?
Spiio sensors and TDR meters use different technologies to estimate soil moisture. They are not interchangeable instruments, and their absolute values are not expected to match. This is common across precision sensor comparisons in turf and agricultural research.
The Spiio sensor's value is in trending and consistency, tracking how your rootzone changes over time at a specific location, not in matching the spot-check reading from a handheld meter. Use your TDR for validation spot-checks, and use GreenCast Connect to track the directional trends that drive your management decisions.
Practical guidance:
Don't set thresholds based on your TDR readings and expect Spiio to hit the same numbers, establish your thresholds based on Spiio data and what you observe on the turf.
Use Data Explorer to compare sensor readings over time and establish your baseline for each location.
If you're seeing a consistent gap between a Spiio reading and your TDR, that gap itself can become useful reference information for that specific area.
Why Doesn't Rainfall Always Spike My Moisture Readings?
Spiio sensors measure at rootzone depth, surface rainfall doesn't always reach the sensor zone quickly.
The trial also examined whether daily precipitation correlated with changes in Spiio soil moisture and salinity readings. The result: precipitation had a weak influence on sensor readings overall.
A few things explain this:
Sensor depth: Spiio sensors are installed in the rootzone. Light or moderate rainfall may not penetrate deeply enough to register a meaningful change at sensor depth - particularly in well-draining rootzone mixes.
Seasonal context matters more: Season had a stronger influence on salinity readings than rainfall did. Fall and winter showed the strongest relationship between precipitation and salinity, consistent with leaching behavior in cooler, wetter conditions.
Small rain events ≠ rootzone change: Routine irrigation and larger rain events will show up in your data. A brief passing shower often won't - and that's accurate information, not a sensor error.
If you see no movement in your moisture readings after a rain event, consider: Was the event significant enough to move water to sensor depth? Is your drainage performing as expected? These are the agronomic questions your sensor data is positioned to help you answer.
Summary
Installation method: does not significantly affect moisture, temperature, or salinity readings. Season and time of year are the dominant drivers.
Spiio vs. TDR: Spiio reads approximately 11% higher than a TDR 350. This is expected. Use Spiio for trending; use TDR for spot validation.
Rainfall: has a weak direct effect on sensor readings. Light rain events often won't register at rootzone depth. Larger events and seasonal patterns will.
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