Buried sensor system

A sensing system including in-ground sensors not requiring battery power. A thermoelectric generator sensor rod includes an upper thermal contact and a lower thermal contact at or near its two ends. When the thermoelectric generator sensor rod is buried in the ground with one end buried more deeply than the other, a temperature gradient in the soil produces a temperature difference between the upper thermal contact and the lower thermal contact. The upper thermal contact and the lower thermal contact are thermally connected to a thermoelectric generator, e.g., by heat pipes or thermally conductive rods. Electrical power generated by the thermoelectric generator powers sensors for monitoring conditions in the ground, and circuitry for transmitting sensor data to a central data processing system.