Couple of things to add that may relate the terms "sodbuster", "stockman" and "jackknife".
First, in my youth, I grew up in Kansas and as I recall from my hazy recollection "sodbuster" was a term first and foremost for the John Deere steel plow, which was the first plow that could reliably punch through the tough, thick sod of the prairie lands of Kansas, Nebraska and Iowa. After that, it became a term for a person who would use a plow, namely farmers, who came to Kansas well after the expansion of free range cattle ranchers. These two camps did *NOT* get along at all and the literal dividing line was barbed wire fencing. Most agricultural museums have displays of barbed wire and their very contentious history, especially surrounding range wars. Crudely, the second wave of settlers included sheep herders, farmers and "civilized law and rights" (translated as get off my land), which flew in the face of the practice of open range ranching (brand 'em and turn 'em loose to feed and then drive them to Dodge City). See:
http://en.wikipedia.org/wiki/Range_wars
So, it makes sense that the Rifleman was called a sodbuster. He was the law and he had a farm.
I believe the term "jack knife" is similarly tied to a name of derision. It appears that "jack knife" is derived from "jack leg knife", which meant crude tools used by unskilled carpenters who lacked more expensive tools and training.
http://www.word-detective.com/2012/01/10/jackleg/
http://www.wordorigins.org/index.php/site/comments/jackleg_jackknife/
So, it would appear that the stockman pattern and the sodbuster pattern literally belong on different sides of the fence and that the fence is made of barbed wire.