Dog,
As smooth as your field is, I would just no till drill it. If you lime it, fertilize it according to a soil test and plant it, the broom sage should go away. I would say that the other grasses and clovers will smother it out too.
Since I am not sure where you are located, by the picture I am going to guess you are in the South.
Here, we planted Orchard grass, Fescue, Red clover and Durana, and the only thing that we is trying to push it's way up is Curly Dock. And it is about 10 plants to the acre. I am hand spraying these. The Durana does cover the ground and forms a dense mat. Or you can plant Durana with bermuda too. They did tests in Alabama, and the clover still remained strong in the bermuda 3 years after planting. It is the only clover that can compete with bermuda.
Now my thoughts on the tractor. If I had a 50 acre pasture, and possibly would obtain more, I would at least aim for a 100 hp tractor. Give or take a few hp. Since I am not hung up on a new tractor, I would aim for a an older model with a cab.
Four wheel drive of course so the front end loader won't mess up the front axle, and you can put out hay anytime no matter what the weather is like.
As the saying goes, you can do small jobs with a big tractor, but you can't do a big job with a small one.
A smaller lighter tractor is limited to what size drill you can pull and what size bushog you use. The drills are very heavy and takes a strong heavy tractor. The bush hogs, depending on if you get a three point hitch or a pull type. I personally like the three point hitch type since I can put it where I want it. But a light tractor can't carry the weight. This size tractor can handle large round hay bales in the front and back. It is costly to abuse a smaller tractor. A 100 hp tractor will handle most anything for that you need to run a small cow operation.
I never did like borrowing someone's tractor to do work that I knew was ahead of me. I would be thinking the neighbor would have that on his mind too. Letting him pay the bucks for one that will get the job done, and me skimping and buying a cheaper, smaller tractor and then go asking for his. I would have to hang my head if I asked. :shock:
My ideal tractor is a John Deere 3150,(96 hp) mechanical front wheel drive, with a cab. You can engage or disengage the front wheels depending on the situation. But if you get under a heavy pulling situation, the front wheels will automatically engage. They made these tractors around the mid 80's to early 90's. A comfortable tractor that you will enjoy operating if you have to spend several hours in it.
This is a fine tractor and is old enough that you don't have to sell any children to obtain one, but you might think about letting a kidney or a lung go.
I would stay away from the after market tractors. Like Mahindra, Kioti, etc....... (that is just my thoughts)
Chuckie