What to measure
For most farms, the key metric is volumetric water content (VWC) by depth — how much water sits in the root zone. Paired sensors often add temperature (affects uptake) and sometimes electrical conductivity (EC) as a salinity proxy. Watching the shallow layer fall faster than the deep layer is your cue to irrigate before plants stall.
- Direct “how full is the sponge” view by depth
- Easy to set thresholds for alerts
- Works across soil textures with calibration
- Temperature: uptake & disease risk
- EC trend: salt build-up on fertigation
- Rain/flow meter overlay for context
Sensor types (quick overview)
Most field kits use capacitance/FDR probes that estimate VWC from the soil’s dielectric properties. They’re affordable and stable when installed correctly. TDR probes are highly accurate but costlier. Tensiometers and granular-matrix sensors report soil water tension (kPa) — a different but useful view of plant effort to extract water. Pick one method and stay consistent for decisions.
Placement by crop & soil
Start with one representative field. Place paired sensors in the main root zone and just below it — e.g., 15–20 cm and 45–60 cm for row crops or veg; deeper for orchards. Avoid wheel tracks and obvious wet/dry spots; install near the crop row and under typical irrigation coverage.
| Crop | Shallow depth | Deep depth | Notes |
|---|---|---|---|
| Vegetables (row) | 15–20 cm | 45–60 cm | Watch fast swings at shallow depth |
| Pasture/forage | 10–15 cm | 30–45 cm | Match to dominant species rooting |
| Orchard/vine | 30–40 cm | 60–90 cm | Place in wetted pattern of emitters |
Irrigation scheduling that works
Define a lower VWC threshold that you don’t want to cross at the shallow sensor (pre-stress) and a recharge target that you aim for after irrigation. Shallow should swing daily; deep should drift slowly and stay within a safe band.
- Pulse rather than flood: smaller, earlier events reduce leaching and runoff.
- Adjust by weather: push thresholds higher in heat/wind; relax in cool/cloudy spells.
- Fertigation: watch EC trends and rinse with plain water if salts climb.
Dashboards & alerts
A simple graph of shallow vs deep VWC tells the story at a glance. Set SMS/app alerts to ping you before the lower threshold. Overlay rainfall and irrigation volume so you can see response curves and fine-tune runtime per block.
- 1 field, 2 depths, 1 gateway (cellular or LoRa)
- Set lower threshold after a full recharge baseline
- Turn on alerts; log irrigations and rain
- Review weekly; nudge runtime, not just start time
ROI snapshot
Even a small cut in runtime (5–15%) across a season usually covers hardware costs, while steadier soil moisture trims stress, tip burn and blossom-end issues. The quieter win: fewer “emergency” night irrigations.
Related products
- Soil-moisture sensor kits
Paired-depth VWC probes with easy install and stable readings.
- Telemetry & dashboards
Gateways, repeaters and apps for alerts, charts and field-by-field thresholds.
FAQ
Do I need to calibrate sensors for my soil?
Factory models work well across textures, but a quick field calibration (full recharge + dry-down) tightens thresholds for your soil and crop.
Can I move sensors between fields?
Yes, but keep them installed long enough to learn the wet-to-dry cycle. Many farms leave one fixed “reference” site and rotate a second kit.
What about salinity on drip/fertigation?
Track EC trend. If it creeps up, shorten pulses and include periodic freshwater cycles to push salts below roots.