Wratherax

I deffinately don't want anything to grow back ever. It's a huge track and there are tons of weeds. I can do it by hand but it'll take forever and a day. That seems like the only option right now though. I'm not sure how well round up will work to get rid of every weed and its roots so that nothing grows back. What kind of salt would I use to prevent regrowth? And what would that cost me?