Fazley Rabbi"We water every morning because that is how we have always done it." On many vegetable farms, fruit orchards, nurseries and greenhouses, watering follows a routine rather than the state of the soil. Some days the soil was already wet, and the water, diesel or electricity was wasted. Other days, after a hot afternoon, the roots were dry long before the next round. Too much water can also wash nutrients away and encourage root problems.
Soil moisture sensors let you see what is happening at the roots, so you water by need instead of by habit.
What the system is made of
- Soil moisture sensors buried at root depth in a few representative spots.
- A small field unit that reads the sensors and sends the readings. In fields far from Wi-Fi, a long-range radio link such as LoRa can carry readings to a gateway at the farm office; where mobile coverage is good, mobile data works too.
- A dashboard or phone app that shows moisture over time for each zone.
- Later, if it makes sense, automatic valves or pump control that water a zone when it gets too dry.
There is rarely mains power out in the field, so field units usually run on a small solar panel and a battery.
Reading the numbers correctly
A sensor reading is only useful if you know what it means for your crop. The right moisture level depends on the crop, the soil type and the growth stage, so I do not give fixed numbers here. Get guidance from your local agriculture extension officer or an agronomist, and calibrate by observation: for the first few weeks, keep watering as usual, watch the readings, and note when plants look stressed or the soil feels wet.
Placement matters as much as the sensor itself:
- put sensors where the roots actually are, not right next to a drip emitter or at the edge of a bed
- use at least one sensor for each zone that is watered separately
- in nurseries and greenhouses, group plants with similar water needs into the same zone
A sensible order of steps
- Pick one zone or one crop where water or pumping is a real cost or a real worry.
- Install a few sensors and just watch the readings for a few weeks.
- Agree your watering points with your agriculture adviser, based on what you observed.
- Add alerts, so you get a message when a zone is drying out.
- Only then automate, if it makes sense. Valves and pump control must be wired by a qualified electrician, with a manual switch so you can always water by hand.
Monsoon, heat and field realities
In the monsoon, the readings can show that the soil is still wet after rain, so you skip a round. In the hot, dry months they show which zones dry out first. Sensors in the ground corrode or drift over time, so check them against a simple hand test now and then and replace them when needed. Rats, cattle and tillage are a bigger threat to cables than the weather, so plan cable routes and protection with that in mind.
If the network or a field unit goes down, the farm must still be watered the old way. Do not let staff lose the habit of checking the soil by hand.
What you do, and where help is useful
You and your farm staff know the crop and the field. An agriculture expert gives you the targets. A technical partner builds the sensors, radio links and dashboard, and makes them survive sun, rain and mud. See IoT device development for what that involves.
A small first step
Put three or four sensors in one zone and watch them for a month alongside your normal routine. If the readings change when or how much you water, extend to more zones. The IoT pilot project page explains how to keep that trial focused, and you can contact me if you would like help setting it up.