Lesson C
Why the same number means different things
A reading of 25% can mean a thirsty crop in one field and a soaked one in the next. The reason is soil — and the fix is calibration. Once you see it, everything else clicks into place.
Two lines that define your soil
Field capacity
25% VWC
Wilting point
12% VWC
Every soil has two important levels. Field capacity is "full" — the most water the soil can hold after the extra has drained away. Wilting point is "empty" — the level below which roots can no longer pull water and the crop wilts. Everything useful happens between these two lines.
Texture changes both lines
Sand, loam and clay hold water very differently. Sandy soil has its full and empty lines low and close together — it dries fast. Clay holds far more water, but grips a large share so tightly that roots can't use it. So the same 25% reading can be near-full in sand and near-empty in clay.
Try the tool below: change the soil type and watch the two lines jump. That movement is the whole reason a sensor must be matched to your field.
Same sensor, different soil
Field capacity and wilting point are not fixed numbers — they depend on your soil. Pick a soil type and watch the "full" and "empty" lines move. That's exactly why a sensor has to be matched to your field.
Choose your soil type
Field capacity
25% VWC
Wilting point
12% VWC
Sandy soils hold little water and drain fast; clay holds much more, but grips some so tightly the roots can't pull it out. The water that actually counts is the gap between the two lines.
How SoilSense does it for you
SoilSense learns where your field's real full and empty lines sit, so you never have to look up a soil table.
So what is calibration?
Calibration simply means finding where your field's own "full" and "empty" lines really sit — not from a textbook, but from your actual soil. The clever part is that the soil tells you, if you watch it over time.
After a good soak, the soil drains and settles at a steady level — that plateau is your field capacity. How long it takes depends on the soil: a few hours in sand, a day or two in heavy clay. The lowest level the crop pulls it down to, just before it shows stress, points to the dry end. Watch a few of these wet-and-dry cycles and your field reveals its own numbers.
How a field finds its own 'full'
Watch a few wet-and-dry cycles. After each irrigation the soil drains — anywhere from a few hours in sand to a day or two in clay — and settles at the same level, and that plateau is field capacity. The lowest point the crop pulls it down to reveals the dry end. This is calibration, and it happens just by watching the soil over time.
- Irrigation or rain fills the soil
- Drains for a few hours, then settles
- Crop slowly dries it down
How SoilSense does it for you
SoilSense watches these cycles for you and detects field capacity automatically — for every crop and every soil type, no manual setup.
Why it's worth it
Without calibration, a moisture percentage is just a number floating in space. With it, every reading becomes a clear answer to the only question that matters: how much water can my crop still reach?
How SoilSense does it for youSoilSense calibrates itself
You don't have to run cycles with a notebook. SoilSense automatically detects field capacity for every field — across all crops and all soil types — by learning from your soil's own wet-and-dry pattern. The science in this lesson runs quietly in the background.