This is a little over my head, but it proves two things:
1. Electical currents CAN pass through soils.
2. Soils are not uniform, they do weird things.
Electroculture: Ohm's Law
Reference
(Shield, 1955)
Shield, R. T. (1955). On Coulomb's law of failure in soils. Journal of the Mechanics and Physics of Solids, 4(1), 10-16.