Don't cheap up on the racks, you don't want your farm to up in flames because you used wood.
Btw, do I see an Owl on one of those wooden pillars?
Thats the power company mounting those Transformers, standard power line poles is what they use many times as seen here.. Thats just the way they build, cant do anything about it, but there is nothing wrong with it, non conductive, treated wood.. (and the Plastic Owl is to keep the birds away.. )
CL