I can share some knowledge on these. Where I come from we call them Whirl-Wind Plows for making Terraces. Back when soil concervation was introduced (late 40s-and 50's some of the farmers had these and plowed-threw up miles of terraces since few people had access to bull dozer service.
I thought my Dad came up with the idea by himself since he build a Twin-Augar machine powered by a Ford flat head V-8 engine and later had one mounted on a WD Allis tractor. I've heard a lot of Farmers done this for extra money working for the USDA-Farmer cost share programs. There is even one that fits the 9N Ford tractors. Just a few years ago My Dad had one like in the picture and liked to finish the terraces after the dozer pushed them up for to get the final contour just right.
Now the big Farmers would just as soon eleminate the Terraces and use the gps to farm every which way. Water ways and Terraces are just an inconvence for the high yeild and big equipment.cleddy