The Nebraska Tests are conducted on concrete pulling a weight with a load cell between the tractor and the weight connector. This data can only be used to compare one tractor tested there againts another tractor tested there.
You can also calculate the drawbar horsepower (drawbar HP=(drawbar force~lbs X speed~ft/sec)/550 from the test points and from that determine the max drawbar power as a function of gear and ground speed. That will tell you the gear to get the most drawbar work done per unit time.
Your soil conditions will be different from the test condtions but this data gives you a starting point to figure out where you should operate your plow.