Soil moisture probes need to be calibrated so they can accurately show when soil is full of water or lacking moisture.
Semios automatically calibrates probes using data from the probe, but the soil must first reach saturation. Saturation occurs when the soil is filled with more water than it can hold, causing extra water to drain downward.
What Is a Drainage Tail?
A drainage tail is the pattern that appears on the soil moisture graph after saturated soil begins to drain.
A drainage tail usually shows:
Soil moisture increasing as the soil profile refills.
A rapid drop after irrigation stops.
A curved “swoop” where the trend line levels out.
This pattern indicates that the soil was saturated, drained quickly, and then settled at the maximum amount of water it can retain.
How Probe Calibration Works
To automatically calibrate, Semios needs to detect 3 drainage tail events within 14 days.
Once the probe is calibrated, 100% soil moisture means the soil is filled to its maximum water-holding capacity.
How to Help Probes Calibrate Faster
Irrigate until you think the soil profile is full.
Stop irrigation.
Check the soil moisture graph after a few hours.
Look for a drainage tail.
If a drainage tail appears, no further action is needed until the next irrigation.
At the next irrigation, irrigate until the soil profile is full again.
Repeat until the system detects 3 drainage tail events within 14 days.
Fastest Calibration Method
To speed up calibration, irrigate the field until it reaches saturation once per day for 3 days in a row.
This can help the system collect the 3 drainage tail events needed for automatic calibration.
After Calibration
After the probe is calibrated, the data can be used with confidence. Semios will continue monitoring probe data throughout the season and may fine-tune calibration as soil conditions change.
FAQs
Why do soil moisture probes need to be calibrated?
Soils vary widely, so probes need calibration to accurately show when soil is full or lacking moisture.
What does saturation mean?
Saturation means the soil contains more water than it can hold, causing excess water to drain downward.
How many drainage tails are needed for calibration?
Semios needs to detect 3 drainage tail events within 14 days.
How long does it take to see a drainage tail?
It may take a few hours after irrigation stops for a drainage tail to appear on the soil moisture graph.
What should I do if I do not see a drainage tail?
Irrigate more and check the graph again after a few hours.
What does 100% mean after calibration?
After calibration, 100% means the soil is filled to its maximum water-holding capacity.
Does calibration stop after the probe is calibrated?
No. Semios continues monitoring the data and may fine-tune calibration as conditions change during the season.