> In a reclaimed farm I volunteered at, the heavy machinery compacted the soil so thoroughly that "regular" plants couldn't grow there until after years of dedi

> In a reclaimed farm I volunteered at, the heavy machinery compacted the soil so thoroughly that "regular" plants couldn't grow there until after years of dedicated soil-rejuvenation projects The effect you may be referring to here is the "plough pan," and it's not just a result of heavy machinery, but also specifically of plough design which features a mouldboard, which drags along the ground creating a layer of heavily compacted soil. Heavy machinery can cause this, too, but ploughing is much more effective at ruining land! This is being somewhat mitigated recently by the increasing use of chisel ploughs, fortunately!