#1). BEWARE! There have been "season" set for p'dogs in some states and if you are out of season--"go to jail". Not aware of NE, but CHECK!!! (then check again, bunny hugger pressure.)
#2). Forest Service in Chadron has charge of much fed grasslands... (yes, forest service runs the grasslands too... government...) Never hurts to inquire there.
#3). East of Haytown? or West? East is "sandhills" really, hills, huge hills of sand--lousy tunnels and less population. West is the pine ridge. Rougher ground but suitable to tunnels for p'dogs.
Regardless, cowboys have told me of shooting p'dogs in the winter on banks of snow sunning. Makes big red spot on snow (unless they miss). First hatch of pups is in the March/April/May time frame and they are coming and going until hard freeze in Oct/Nov. Then slow down. Late April/May the pups will be about adult size. Almost. (and ignorant as in "dumb"...)
Wish I could go along. Had family there, "in the ground" now. LUCK.