A basic setup involves a wooden pole, a copper spiral winding upward, and a grounding spike or buried wire

https://blogfreely.net/galenacmeo/electro-culture-gardening-safety-best-practices-for-home-gardeners

A basic setup involves a wooden pole, a copper spiral winding upward, and a grounding spike or buried wire, positioned near crops to capture atmospheric ions and gently influence local electrostatic conditions.