I have learned on this new farm of ours that the Walnuts I am used to seeing in Nebraska definitely have a different looking bark than the ones here in KS. We are only 4.5 hours away, but it is defintitely noticeable.
Its far more difficult to tell without the leaves.... I thought it looked like walnut as well..... If it is a walnut it is big enough where you should find at least traces of the nuts and hulls around the base.
I always tell folks to mark the tree and then wait until it leafs out and try to get us pictures of the leaves. You can normally at least narrow it down to the family it belongs to that way.
To me, it doesn't look like any kind of tree that would have compound leaves, it's too "twiggy". The bark looks a lot like a slippery elm that once stood in my yard, but it's hard to I.D. just by the bark.
I was focusing so much on the last picture, I just noticed there are 2 different trees.
First one could likely have compound leaves (Possibly walnut or ash) 2nd tree looks like Slippery Elm or American Basswood. FWIW