Capacitive Soil Sensor: A type of sensor that measures the dielectric permittivity of a surrounding medium. In soil, this permittivity is highly dependent on water content.
Unlike cheap resistive sensors that corrode in weeks, VarshaKrishi uses industrial-grade capacitive sensors fully encased in epoxy, ensuring a multi-year lifespan in harsh Indian agricultural conditions.
A capacitive soil sensor measures soil moisture by treating the soil as the dielectric of a capacitor: the probe emits a high-frequency signal and measures how the surrounding soil stores charge. Because water's dielectric constant (~80) is vastly higher than dry soil's (~4), the reading tracks water content closely. Crucially, the electrodes never touch the soil electrically — they are coated — so the probe does not corrode the way cheap resistive sensors do.
Resistive sensors (two exposed metal prongs) cost less but corrode within weeks in fertilised, irrigated soil and their readings drift as the electrodes degrade. For a sensor that must survive an entire Indian kharif season buried in the ground, capacitive measurement is the minimum viable technology.
VK-Series nodes use coated capacitive probes at multiple depths, each factory-calibrated and field-adjustable for soil texture. Combined with 15-minute reporting over LoRa, a single node cluster produces the season-long moisture record that irrigation models require.
Quality coated capacitive probes routinely run multiple seasons; the sensing surface is insulated from the soil so there is no galvanic corrosion. Resistive probes, by contrast, commonly fail within one season in fertilised soil.
Yes — a one-time texture calibration (sand/loam/clay) maps the dielectric reading to accurate volumetric water content. VarshaKrishi nodes ship with per-texture curves selectable at deployment.
See also: Volumetric Water Content, LoRaWAN — or browse the full smart farming glossary.
Discover how VarshaKrishi utilizes this technology in our offline-first systems across rural India.
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