Put a 100w incand. lamp across the 4v and measure it again. If the voltage drops to 2v there is about 10 Ω (resistivity of the soil?) in series with this voltage.i can take my meter and stick one probe in the ground and touch anything metal and read 4 volts.
if im sweaty there is a tingle.
With this load you may see different voltages depending on what metal you touch, with lower voltages being farther from the source, if there is a single source.
Using your body as an ammeter:
"Tingle" = ~4mA, give or take.
4v/4mA = 1k skin resistance; pretty low for a small contact area, but you have damp, salty, skin.
No tingle = <1 mA means > 4kΩ.
See table 1 in this link.