Equipment and Principles

Implementing Smart Irrigation: Equipment and Principles

The implementation of smart irrigation requires the use of the following connected hardware:

• Soil moisture probes (capacitive or tensiometric)

• Valve controllers

• Water meters

• Pressure sensors

• Weather stations (to provide a comprehensive overview of water input)

Metrological Principles of Probes

A capacitive probe determines the soil water content by measuring the variation in the soil's electrical capacitance. This variation is directly linked to its water content via dielectric permittivity. The probe provides a percentage value: the Volumetric Water Content (VWC).

A tensiometric probe determines water availability for plants by measuring the soil's matric potential—the force with which water is held by the soil matrix. This value is directly related to how easily plants can extract water. The probe provides a water tension reading in centibars (cbar).

Comparison Table

Criteria	Capacitive Probe	Tensiometric Probe
Measured Variable	Volumetric Water Content	Matric Potential
Principle	Dielectric Permittivity	Water Vacuum/Tension
Information Provided	Quantity of water in the soil	Water availability for plants
Measurement Range	Wide (dry to saturated soil)	Limited to moist soils
Maintenance	Low	Regular
Soil Sensitivity	Texture, salinity	Less sensitive to texture

The use of capacitive probes is generally simpler for "non-expert" users compared to tensiometric probes, making them the preferred choice for smart irrigation.

Capacitive Probes Offered by Greencityzen:

• Waterscout SM100: The soil volume "sensed" by the probe is a cylinder 6 cm long by 2 cm wide.

• HSTI Hydrascout: The soil volume "sensed" by the probe is equivalent to the size of a volleyball (sensing radius around a 38 mm diameter probe).